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NLG Users Repair Logs and Other Ramblings. Request your very own topic. Just ask any site staff. => Channelmaniac's Arcadecomponents' Old School Repair Logs => Topic started by: channelmaniac on May 23, 2014, 08:40:08 PM

Title: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:40:08 PM
Fixed: AES JAMMA system
Symptom: Would only play the supplied Puzzle De Pon cartridge.

This was a strangely modified home game system. It had a custom BIOS chip and an added on chip that was used to add in a test switch and game credits. It also had an external audio amplifier board and a JAMMA edge connector/wires soldered in to allow it to be played in an arcade.

Pulled the added-on 74LS245 IC, wiring, test switch, and custom BIOS chip. Erased and reprogrammed the custom BIOS chip with UniBIOS code. Resoldered cracked solder joints on the external audio amplifier. System will no longer take quarters or have an arcade style test switch with coin reporting, etc., but will now play all AES games as requested by the owner.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:40:24 PM
Subject: Troubleshooting vertical lines on the MV6 6-slot system

Do you have vertical lines on the screen either on the moving foreground objects or background objects on your 6 slot board?

On the 6 slot board there are a bunch of 74LS251 8 to 1 data selector ICs. The ICs nearest slot 6 are for the foreground objects and the ICs nearest slot 1 are for the background objects.

The easiest way to check these chips for the bad one is to put a test cart in slot 5 and flip DIP switch 8 to pause the screen where you can see the problem images on screen.

Next take the logic probe and check pin 15 of each 74LS251. Look for the IC with no signals on that pin. If you find one without a signal then check the trace between the slot and that pin.

Not fixed? Next check pin 4 of each 74LS251 for data output. If one is missing then replace the IC.

Still not fixed? Next take the logic probe and put it on pin 15 of each 74LS251. Slide the tip over to where it momentarily shorts between pin 15 and 16. Look at the screen for lines. See lines pop up? That's not the chip you are looking for. Finally find one that doesn't pop up any extra lines when you short it across? OK. That's the data line that is the problem. Follow pin 4 of that chip and find where it connects to go to the bottom board.

Can't find where it goes to the connector? Check a neighboring 74LS251 IC and see where it goes. If you can find it then check for a bad trace between the suspect data line on pin 4 and the connector to the bottom board and patch it.

Still not it? Check the connection between the top and bottom board. If there is no signal then desolder the connector, disassemble it, pull out the offending connector piece, clean it, reassemble, and resolder it back in place. Test it.

Still no? Follow that trace to the chip it goes to and if the trace is good then replace the chip.

If that doesn't do it then call a priest and have the board exorcised.

Enjoy!
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:40:40 PM
Model: MVS MV-4 (4 slot)
Symptom: Missing background graphics

There's a 74LS138 on the top board. It's a 3 to 8 decoder. It's used to enable the slot wanted. Not part of the repair, but just wanted to doc it on the forum. Also, there are a LOT of 74LS244 buffers & 74LS245 latches on the board. Each one is hooked together with the neighboring chip that is doing the same function on each of the different slots. In other words, each cartridge slot has multiple buffers and latches. Each latch for specific connections (program data lines 0-8, for example) on the cartridge slot has their board side connections (not cartridge side connections) tied together to the connectors that take the signal to the bottom board.

Now, on to the repair:

Test Cart used: Shock Troopers, 2nd Squad.

This top board had a totally white screen with the exception of the "insert coin" words in the center and the "credit 0" at the bottom right and even that text was mispelled...

Used a logic probe to check each and every chip for input and output logic levels. Found a 74LS244 next to slot 4 that had incorrect levels for input vs. output. In tracing the pins on the chips I discovered that there is a chip doing the same thing for each of the slots and they are all tied together. That makes 4 video ROM buffers - one for each slot - all tied together when the connect to the bottom board.

Why does it matter that they are tied together? Well, when one shorts it tends to draw excessive current through the others and takes them out too.

Replaced the 74LS244 chips at locations N4, J4, E4, and A4 to fix.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:40:53 PM
Model: MVS MV-4
Symptom: Cartridges do not work. Crosshatch pattern is all you get on the screen, no matter what slot. Unusual in that the problem follows the top board when swapping boards out.

Resolution: There is a 74F138, 3 to 8 decoder, at position A2 that determines which slot is active. Fixed broken trace on one of the 3 enable lines to allow the system to switch the slots and access the cartridges.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:41:16 PM
Model: MVS MV-4
Symptom: Vertical lines in the graphics on slot 3.

Resolution: The graphics ROMs connect to the system board through a series of 74F253 ICs. These are dual 1 of 4 line selectors. Pin 21B on the bottom cartridge slot connector's data wasn't seen on the output (pin 9) of the 74F253 at position D1. Patched the trace to fix.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:41:24 PM
Model: MVS MV-6
Symptom: Stuck in Watchdog (a.k.a. Click of Death)

6 slot board would constantly reset... Logic probe on pin 18 of the CPU confirmed that the reset line kept bouncing. This was the watchdog circuit trying to kickstart the CPU into booting.

Checked the data lines and enable lines on the work RAM - checked fine.

Checked the enable lines on the backup RAM and discovered that the WE* line on one of the RAMs was missing its signal and the OE* line on both RAM chips was missing its signal.

Repaired the bad traces to fix the bottom board.

It appears that something corroded the plate-thrus on the board. Seems to be a common occurrence on all models of the MVS boards.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:42:05 PM
Model: MVS MV-6
Symptom: Graphics corruption

Found and repaird 4 gouged traces on the top board. Traces were damaged due to insufficient padding when item was shipped. The top cover was bent and the traces were gouged by it.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:42:22 PM
Board: MVS MV-4
Symptom: Crosshatch of death

Crosshatch of death is where the board shows the self test crosshatch screen. It is not recognizing any cartridges inserted into the board.

This is a common problem on the older, larger 4 slot board. The NiCD backup battery will leak and eat through traces that run under and next to it. Trace the lines with a multimeter from the connector next to the battery and run jumpers to patch any bad traces.

That connector is what the system uses to access the program ROMs on the cartridges. If it can't read and run the program then it cannot detect and use the cartridges. ;)
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:43:16 PM
Model: MVS MV-4F (newer, smaller 4 slot)

Wow. This one was a bitch. Typical crosshatch problem, but the battery was not leaking and no traces were damaged near it. (Although the battery isn't in the same proximity to the traces on this board like on the older 4 slot board. Thus, this board doesn't suffer from the same Crosshatch of Death problem)

I spent a lot of time troubleshooting and pinning out the SMT chips on the top board before moving down to the bottom board.

The top board has the NEO-G0, NEO-244, and NEO-253 chips on it.

It appears from the troubleshooting that the NEO-G0 chip is made up of 4 74LS245 chips. I haven't pinned out the 244 or the 253 chips but assume that they are similar (4 x 74LS244 and ? x 74LS253 chips)

Enjoy the pinouts:
Code: [Select]
NEO-G0 chip at location D1

1 - d3 to cart 4
2 - d0 - cn10-4a
3 - d1 - cn10-5a
4 - d2 - cn10-6a
5 - d3 - cn10-7a
6 - d0 to cart 3
7 - d1 to cart 3
8 - d2 to cart 3
9 - d3 to cart 3
10 - gnd
11 - d4 to cart 3
12 - d5 to cart 3
13 - d6 to cart 3
14 - d7 to cart 3
15 - d4 - cn10-8a
16 - d5 - cn10-9a
17 - d6 - cn10-10a
18 - d7 - cn10-11a
19 - N/C?
20 - N/C?
21 - d4 to cart 4
22 - d5 to cart 4
23 - d6 to cart 4
24 - d7 to cart 4
25 - gnd
26 - vcc
27 - d8 to cart 3
28 - d9 to cart 3
29 - d10 to cart 3
30 - d11 to cart 3
31 - d8 - cn10-12a
32 - d9 - cn10-13a
33 - d10 - cn10-14a
34 - d11 - cn10-15a
35 - d8 to cart 4
36 - d9 to cart 4
37 - d10 to cart 4
38 - d11 to cart 4
39 - Connects to E1-39 & CN9-14
40 - Connects to 52 & to B1 52/40
41 - N/C?
42 - gnd
43 - d12 to cart 3
44 - d13 to cart 3
45 - d14 to cart 3
46 - d15 to cart 3
47 - d12 - cn10-16a
48 - d13 - cn10-17a
49 - d14 - cn10-18a
50 - d15 - cn10-19a
51 - CN9 - 13b & E1-51
52 - Connects to 40 & to B1 52/40
53 - d12 to cart 4
54 - d13 to cart 4
55 - d14 to cart 4
56 - d15 to cart 4
57 - gnd
58 - vcc
59 - N/C?
60 - gnd
61 - gnd
62 - d0 to cart 4
63 - d1 to cart 4
64 - d2 to cart 4

--------------

NEO-G0 chip at location B1

1 - d3 to cart 2
2 - d0 - cn10-4a
3 - d1 - cn10-5a
4 - d2 - cn10-6a
5 - d3 - cn10-7a
6 - d0 to cart 1
7 - d1 to cart 1
8 - d2 to cart 1
9 - d3 to cart 1
10 - gnd
11 - d4 to cart 1
12 - d5 to cart 1
13 - d6 to cart 1
14 - d7 to cart 1
15 - d4 - cn10-8a
16 - d5 - cn10-9a
17 - d6 - cn10-10a
18 - d7 - cn10-11a
19 - N/C?
20 - N/C?
21 - d4 to cart 2
22 - d5 to cart 2
23 - d6 to cart 2
24 - d7 to cart 2
25 - gnd
26 - vcc
27 - d8 to cart 1
28 - d9 to cart 1
29 - d10 to cart 1
30 - d11 to cart 1
31 - d8 - cn10-12a
32 - d9 - cn10-13a
33 - d10 - cn10-14a
34 - d11 - cn10-15a
35 - d8 to cart 2
36 - d9 to cart 2
37 - d10 to cart 2
38 - d11 to cart 2
39 - Connects to C1-39 & CN9-13
40 - Connects to 52 & to D1 52/40
41 - N/C?
42 - gnd
43 - d12 to cart 1
44 - d13 to cart 1
45 - d14 to cart 1
46 - d15 to cart 1
47 - d12 - cn10-16a
48 - d13 - cn10-17a
49 - d14 - cn10-18a
50 - d15 - cn10-19a
51 - CN9 - 12b & C1-51
52 - Connects to 40 & to D1 52/40
53 - d12 to cart 2
54 - d13 to cart 2
55 - d14 to cart 2
56 - d15 to cart 2
57 - gnd
58 - vcc
59 - N/C?
60 - gnd
61 - gnd
62 - d0 to cart 2
63 - d1 to cart 2
64 - d2 to cart 2

OK...

After all of that I moved to the bottom board and checked the interface chips that connect the bottom board to the top board. WOW There were a lot of missing and incorrect signals coming from those chips. My logic probe got a workout on this system.

Replaced the following bad chips to fix it:

74LS245 @ N1
74AS245 @ M4
74F245 @ N9
74F245 @ L9
74AS245 @ F11
74AS245 @ D11
74AS245 @ C11

I'm thinking that someone MUST have disconnected the two boards with the system powered up. That's the only thing I could think of that would've taken out all those chips at once.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:44:26 PM
Model: MVS MV-2
Symptom: Multiple - Video RAM Error $8000 and Calendar Error

Had an MVS 2 slot sent to me for repair that had a couple of issues. The first was the typical Video SRAM issue at $8000 - The CXK5814 chips were both bad.

The second issue was the game was stuck at the green screen. It would boot to the Backup RAM test if you turned all the DIPs on and would work fine with a UniBIOS chip. It was a Calendar Error problem. This problem does not always show up as the text "Calendar Error" on the screen. It may manifest itself as a "stuck on green screen" problem.

Armed with my trusty logic probe the calendar IC (D4990) checked like this:

Code: [Select]
Pin 1 - H
Pin 2 - H
Pin 3 - H
Pin 4 - L
Pin 5 - H
Pin 6 - L
Pin 7 - L

Pin 8 - L
Pin 9 - L
Pin 10 - H
Pin 11 - H
Pin 12 - Nothing
Pin 13 - H
Pin 14 - H

Hmmm... Crystal looks to be defective.

Grabbed a working board and the signals look like this:

Code: [Select]
Pin 1 - H
Pin 2 - H
Pin 3 - H
Pin 4 - L
Pin 5 - H
Pin 6 - L
Pin 7 - L

Pin 8 - L
Pin 9 - L
Pin 10 - Pulsing H/L
Pin 11 - H
Pin 12 - H
Pin 13 - H
Pin 14 - H

OK - Really looks like a bad crystal now. Swapped one off a parts board and POOF. System is now working.

Hope the logic readings help you troubleshoot your system if you ever need it.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:44:38 PM
Model: MVS MV-4
Symptom: Stuck in Watchdog (Click of Death)

Board gave garbage on the screen with constant clicking sound. In other words, it was dead and the watchdog circuit was resetting the CPU.

Replaced a shorted 74AS245 at location B7. It was shorted internally and was getting red hot. Board powered up with a Video RAM error at 8000. Replaced the lower bank IC at L11 to finish repairing the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:44:48 PM
Model: MVS MV-2
Symptom: Will not boot. Resets.

This one is a 2 slot that was shipped to me with the description of "stuck on green screen with garbage"

When it arrived I hooked it up and it would get to the green screen as normal but would then reboot. This cycle repeated indefinitely. Battery had leaked and there was corrosion on some of the board traces. It was not a Calendar Error issue as it rebooted. Calendar error would've manifested itself by freezing on the green screen and not rebooting.

Pin 20 of the backup RAM was missing its signal. Removed the battery, cleaned the board, replaced the corroded 74HC32 at location J2, and patched a corroded trace between J2 Pin 2 and transistor C1815 to fix. Replaced the battery with a new one and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:45:13 PM
Model: MVS MV-4
Symptom: Garbage on screen / Click of Death (Stuck in Watchdog)

This one had some physical damage that someone did a half-ass repair on. It's ugly as sin but the trace they patched is working.

The board would display nothing but garbage and would constantly do a click click click - watchdog circuit was trying to restart the system.

Replaced 2 74LS245 ICs at locations B7 and B8. Both were shorted and getting very hot.

Board was still in watchdog restart.

Patched a bad trace on data line D16 between the upper Backup RAM and the upper Data RAM. Now the board would constantly go through self test and restart with garbage on the screen. It was a different restart than with the watchdog circuit.

Examined the board under a magnifying glass and found one more gouged trace the previous tech missed between data line D1 on the CPU and pin 60 on the PRO-C0 chip. Patched the trace and the board is now running fine.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:45:23 PM
Model: MVS MV-2
Symptom: Vertical bars through graphics

This 2 slot had some bad battery damage and vertical bars through the Neo Geo logo and certain sprites.

Checked the ROM Data Lines on the cart slot pins A19/B19 through A26/B26 with the logic probe. Cart was working fine. Followed the traces to the NEO-257 IC at J2 with the logic probe. Traces were good. Followed the outputs of the NEO-257 IC to the NEO-ZMC2 IC. Two of the data lines (D0 and D1) were missing from the NEO-257.

Replaced the surface mount NEO-257 IC at J2 with one pulled from a parts board to fix.

Cleaned the board & replaced the battery as well.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:45:32 PM
Model: MVS MV-2
Symptom: Random Backup RAM errors

The control signals were missing from the Backup RAM chips. Installed a UniBIOS to further check the board and it would constantly crash. A close inspection of the board revealed corrosion damage from either liquid or rodents. Cleaned the board and found that the trace for address line A13 was damaged coming off of the CPU. Patched the trace and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:45:41 PM
Troubleshooting with the UniBIOS chip

The UniBIOS chip can be used to bypass Backup RAM, Calendar Error, and other problems to allow for a board to be further tested. If the system bypasses errors and runs then odds are it will be an easier repair.

If it's crashing then there are other problems that are masked by the error message. Check the BIOS socket, look for gouged traces, and check for corroded plated thru holes.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:45:49 PM
Model: MVS MV-2
Symptom: Backup RAM error

Board was giving a Backup RAM error (written 5555 read 5500.)

The "00" typically means the chip is missing control signals.

Checked the board and it had 2 bad traces going to the control lines of the 2nd Backup RAM IC. Patched the traces and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:46:03 PM
Model: MVS MV-4
Symptom: Corrupted Graphics

The Neo Geo logo screen had the words broken into jumbled blocks and there were "0" (zeros) down the left and right sides of the screen.

Checked the board for broken traces. Did not find any. Swapped the top board with my test board. Same problem - it's on the bottom board. Replaced the 2 74LS244 buffer chips that were driving the address lines for the graphics ROMs. No change.

This was still an address line problem since the problems were in blocks and not in vertical lines on the screen.

Took the logic probe and checked each address line at the top board. Noticed one of the lines only had a slow pulse on it instead of activity. Shorted it to the next address line over and the zeros went away and there was just garbled graphics. Traced that line back and found where there was a very small area of board between connector CN8 and the edge of the board that had taken a hit.

Patched the broken trace to fix the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:46:32 PM
Here's a pinout for the custom NEO-ZMC2 chip

The NEO-ZMC2 IC is documented incorrectly on a few websites. It does NOT multiplex sound data. Instead it takes the foreground and background graphics (16 bits each for a total of 32 bits) and interfaces with a single 8 bit (8 traces) connection to the Neo graphics subsystem.

On the older 2 slot the ZMC2 pins GAD0 through GAD3 and GBD0 through GBD3 connect to the NEO-C0 IC to get this multiplexed graphics data into the video subsystem.

Standard conventions apply - Vcc = +5v, Gnd = ground, a "*" means active low (when there's a bar over top of the pin's function), etc...

RJ

Code: [Select]
NEO-ZMC2
1 - GAD2
2 - GND
3 - GAD3
4 - DOTA
5 - LOAD
6 - EVEN
7 - H
8 - DOTB
9- NC
10- GBD0
11- GBD1
12- Gnd
13- GBD2
14- GBD3
15- C1
16- C1
17- C2
18- C3
19 - C4
20 - C5
21 - C6
22 - C7
23 - Gnd
24 - C8
25 - C9
26 - C10
27 - C11
28 - C12
29 - C13
30 - C14
31 - C15
32 - C16
33 - Vcc
34 - C17
35 - C18
36 - C19
37 - C20
38 - C21
39 - C22
40 - C23
41 - C24
42 - Gnd
43 - C25
44 - C26
45 - C27
46 - C28
47 - C29
48 - C30
49 - C31
50 - 12M
51 - NC
52 - Gnd
53 - MA11
54 - MA12
55 - MA13
56 - MA14
57 - MA15
58 - MA16
59 - MA17
60 - MA18
61 - MA19
62 - MA20
63 - Gnd
64 - MA21
65 - A8
66 - A9
67 - A10
68 - A11
69 - A12
70 - A13
71 - A14
72 - A15
73 - Vcc
74 - A0
75 - A1
76 - SORD0 (Can't quite make out the writing)
77 - CS*
78 - CSDOT*
79 - GAD0
80 - GAD1
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:47:28 PM
From Kyuusaku on the Neo-Geo.com forums:

Here's the ZMC2's early counterpart at least for home carts:

ALPHA-8921 / PRO-CT0

Code: [Select]
D1 odd.15 1 64 VCC
D3 odd.19 2 63 VCC
D5 odd.24 3 62 odd.26 D6
D7 odd.28 4 61 odd.22 D4
D8 odd.14 5 60 odd.17 D2
D10 odd.18 6 59 odd.13 D0
D12 odd.23 7 58 A8
D14 odd.27 8 57 A7 inputs?
D9 odd.16 9 56 A5
D11 odd.20 10 55 A9
D13 odd.25 11 54 test?
D15 odd.29 12 53 test?
D0 even.13 13 52 test?
D2 even.17 14 51 test?
D4 even.22 15 50 gnd
D6 even.26 16 49 gnd
D1 even.15 17 48 B39
D3 even.19 18 47 B38
D5 even.24 19 46 B37 mux outputs?
D7 even.28 20 45 B36
D8 even.14 21 44 gnd
D10 even.18 22 43 gnd
D12 even.23 23 42 B35
D14 even.27 24 41 B34
D9 even.16 25 40 B33 mux outputs?
D11 even.20 26 39 B32
D13 even.25 27 38 test?
D15 even.29 28 37 test?
B30 29 36 test?
select inputs? B31 30 35 test?
GND 31 34 test?
GND 32 33 test?

Notes:
test? = NC pins or pins with tracks that ONLY lead off the board for testing.
A## are not address lines but home cart pin numbers as are B##

Don't mind the bad formatting
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:47:57 PM
Here's the NEO-257 @ location J2 on the 2 slot board. (MV-2)

Code: [Select]
Pin - function/chip connection/slot connection (cartridge pin function)
1 - Slot 2 B26 (CA15)
2 - Gnd
3 - Gnd
4 - Slot 1 A19 (CA0)
5 - Slot 2 A19 (CA0)
6 - Slot 1 B19 (CA1)
7 - Slot 2 B19 (CA1)
8 - ZMC2 - 15 C0 (CA0)
9 - ZMC2 - 19 C4 (CA1)
10 - Gnd
11 - ZMC2 - 16 C1 (CA2)
12 - ZMC2 - 20 C5 (CA3)
13 - Slot 1 A20 (CA2)
14 - Slot 2 A20 (CA2)
15 - Slot 1 B20 (CA3)
16 - Slot 2 B20 (CA3)
17 - Input (Slot) Select 1/2
18 - Gnd
19 - Slot 1 A21 (CA4)
20 - Slot 2 A21 (CA4)
21 - Slot 1 B21 (CA5)
22 - Slot 2 B21 (CA5)
23 - ZMC2 - 17 C2 (CA4)
24 - ZMC2 - 21 C6 (CA5)
25 - Gnd
26 - Vcc
27 - ZMC2 - 18 C3 (CA6)
28 - ZMC2 - 22 C7 (CA7)
29 - Slot 1 A22 (CA6)
30 - Slot 2 A22 (CA6)
31 - Slot 2 B22 (CA7)
32 - Slot 2 B22 (CA7)
33 - Gnd
34 - Gnd
35 - Vcc
36 - Slot 1 A23 (CA8)
37 - Slot 2 A23 (CA8)
38 - Slot 1 B23 (CA9)
39 - Slot 2 B23 (CA9)
40 - ZMC2 - 24 C8 (CA8)
41 - ZMC2 - 28 C12 (CA9)
42 - Gnd
43 - ZMC2 - 25 C9 (CA10)
44 - ZMC2 - 29 C13 (CA11)
45 - Slot 1 A24 (CA10)
46 - Slot 2 A24 (CA10)
47 - Slot 1 B24 (CA11)
48 - Slot 2 B24 (CA11)
49 - NC
50 - NC
51 - Slot 1 A25 (CA12)
52 - Slot 2 A25 (CA12)
53 - Slot 1 B25 (CA13)
54 - Slot 2 B25 (CA13)
55 - ZMC2 - 26 C10 (CA12)
56 - ZMC2 - 30 C14 (CA13)
57 - Gnd
58 - Vcc
59 - ZMC2 - 27 C11 (CA14)
60 - ZMC2 - 31 C15 (CA15)
61 - NC
62 - Slot 1 A26 (CA14)
63 - Slot 2 A26 (CA14)
64 - Slot 1 B26 (CA15)
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:48:33 PM
If you look at a 74257 data sheet you will see that it is a 2 to 1 data multiplexer. The NEO-257 is simply 4 of these chips combined into one package to save some board space.

The hard part is that I cannot tell which pins are for "output enable" like on the 74257 since the only function that isn't set to ground or +5v is the one for input select. It appears these chips are set to always be enabled.

Enjoy!

Code: [Select]
NEO-257 pinouts

1 - Input 16B
2 - Gnd
3 - Gnd
4 - Input 1A
5 - Input 1B
6 - Input 2A
7 - Input 2B
8 - Output 1
9 - Output 2
10 - Gnd
11 - Output 3
12 - Output 4
13 - Input 3A
14 - Input 3B
15 - Input 4A
16 - Input 4B
17 - Input Select A/B
18 - Gnd
19 - Input 5A
20 - Input 5B
21 - Input 6A
22 - Input 6B
23 - Output 5
24 - Output 6
25 - Gnd
26 - Vcc
27 - Output 7
28 - Output 8
29 - Input 7A
30 - Input 7B
31 - Input 8A
32 - Input 8B
33 - Gnd
34 - Gnd
35 - Vcc
36 - Input 9A
37 - Input 9B
38 - Input 10A
39 - Input 10B
40 - Output 9
41 - Output 10
42 - Gnd
43 - Output 11
44 - Output 12
45 - Input 11A
46 - Input 11B
47 - Input 12A
48 - Input 12B
49 - NC
50 - NC
51 - Input 13A
52 - Input 13B
53 - Input 14A
54 - Input 14B
55 - Output 13
56 - Output 14
57 - Gnd
58 - Vcc
59 - Output 15
60 - Output 16
61 - NC
62 - Input 15A
63 - Input 15B
64 - Input 16A
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:48:55 PM
Troubleshooting Color and Sync problems on MVS boards:

This post is from the perspective of repairing a MVS 2F board - the newer version of the 2 slot - but will work for most other MVS boards.

The output of the video subsection will go through the NEO-G0 chip then on to the Palette RAM (8k x 8bit SRAM) and the 74LS273 latches. From there it goes to a resistor ladder per color with a couple of the lines being buffered/amplified (higher current) by a 74LS05 IC before going out to the JAMMA connector.

When troubleshooting MVS color issues take a moment to divide the problem into sections.

1. Palette, or Color RAM error
2. No Sync (either horizontal or vertical)
3. Missing or incorrect colors

Part 1: Palette, or Color RAM error

If there are Palette RAM problems this can be caused by a problem in any of the ICs connected to that data bus: NEO-G0 chip, Palette SRAM, or the 74LS273 latches. The easiest thing to do is to power OFF the board and check the data lines on the SRAM ICs for shorts to +5v or ground connections. If there are none then replace the SRAM first.

If there is a short, remove the 74LS273 ICs first as they will be the most likely culprit. Check the data lines again. If the short is gone, replace the latches. If not, move on to the next chips, the SRAM. Repeat tests and replace the NEO-G0 last.

Part 2: No Sync (either Horizontal or Vertical)

The sync line goes from the NEO-I0 chip through a 100 ohm resistor to the JAMMA connector. It's also tied high to +5v through a 470 ohm resistor. Check both resistors. Replace if bad. If there is still no sync, replace the NEO-I0 chip.

Part 3: Missing or incorrect colors

Missing colors can be caused by any of the parts in the output section. Unless there's an esoteric problem with the Color RAM the digital part can be mostly taken out of the equation.

The output is made up of the 74LS273 latches, a series of resistors forming a ladder network, and 74LS05 Hex Buffer/Inverter IC.

With the power OFF, check the inputs and outputs of the 74LS05 IC for shorts to either +5v or ground connections. Replace the IC if any shorts are found. If there are shorts but the 74LS05 IC isn't it then replace the 74LS273 ICs. Next check the resistors for any that are burned.

If the RGB outputs are shorted the most likely culprits will the the 220 ohm and 150 ohm resistors as these are the lower value resistors. (The lower the value the higher the current that will flow through during a short.) check these resistors with an ohmmeter and replace any that are not reading correctly.

The next step is to check the outputs of the 74LS273 ICs with a logic probe. On the datasheet there are D and Q pins listed. The D is the input, the Q is the output. Check for signals on both sides. Replace the ICs that have inputs but no outputs between their D and Q pins.

Hook everything back up after replacing the parts and give it a test!

I had a board in the shop with missing red colors. There were no other symptoms on this board such as lines through images, etc... just screwy looking colors.

I replaced the NEO-G0 IC before stepping back and taking a better look at the circuit. After analyzing the circuit I replaced a shorted 74LS05 IC and two bad resistors to fix the board.

The 150 ohm and 220 ohm resistors were bad and the 74LS05 gate driving the 150 ohm resistor was shorted to ground.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:51:29 PM
Model: MVS MV-4
Dignosing bad RAM ICs

Board is a NEO-MVH MV4 (4 slot)

Code: [Select]
Backup RAM Error:

Address    Write  Read
00D01406   AAAA   AA2A

The Read code is broken up into 2 parts... AA and 2A

The first 2 characters are the upper bits and are handled by the IC at D9
The second 2 characters are the lower bits and are handled by the IC at F9

--------

Code: [Select]
Video RAM Error:

Address    Write  Read
00000607   5555   5455

Same thing here... the Read code is broken up into 2 parts... 54 and 55

The first 2 characters are handled by the IC at L9
The second 2 characters are handled by the IC at K9

--------

Work RAM is laid out backwards from Backup RAM and Video RAM on the NEO-MVH MV4

Code: [Select]
Work RAM Error:

Address    Write  Read
xxxxxxxx   AAAA   AABA

(Yeah, I was too lazy to write down the exact address of the error...)

The first 2 characters are the upper bits and are handled by the IC at H9
The second 2 characters are the lower bits and are handled by the IC at G9
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:52:05 PM
Model: MVS MV-6
Diagnosing bad RAM ICs

Here's the info on the 6 slot board:

Upper Backup RAM: E9
Lower Backup RAM: F9

Upper Video RAM: L9
Lower Video RAM: K9

Upper Work RAM: J9
Lower Work RAM: H9

Just keep in mind that if you have an error at the bottom boundary then you need to check traces.

For example a video error of:

Code: [Select]
Video RAM Error:

Address    Write  Read
00000000   5555   5455

Shows up on the zero boundary. You need to check to see if the traces (wiring that is on the circuit board) are all good. A bad trace or a bad chip can each cause this type of error.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:53:33 PM
Model: All MVS boards
Troubleshooting Backup RAM Errors

If you see this for a Backup RAM Error:

Code: [Select]
Backup RAM Error:

Address    Write  Read
00D00000   5555   0000

Then you have a different problem all together.

This is caused by the chip not being selected properly for read/write access. This is almost always (well, I'd say > 99.5%) a problem with the chip or with the trace that is controlling the SRAM and NOT with the SRAM.

Look for broken traces whether from battery leakage or someone scraping something across the board which physically damaged the traces. If that's not it then trace back the chip control traces to see what chip is feeding it.

On the 32k x 8 SRAM ICs (the 62256 or equivalent) that are used for the Backup, Work, and Video RAM that would be:

Code: [Select]
Pin 27: *write (also known as *WE) - Write Enable
Pin 22: *G (also known as *OE) - Output Enable
Pin 20: *E (also known as *CE) - Chip Enable

OK, OK... the * in front means it is an active low signal. If it's high, it's not being signaled. If you get NO signal from your logic probe on one of the pins then you have an open trace for sure.

Pin 20: should always be grounded on the Work RAM and Video RAM. That pin is directly connected to ground and if it isn't then you have a physically damaged trace. On the Backup RAM it is used to put the chips into low power standby mode.

Pin 22 & 27 connect to different chips. These are the ones you are most concerned with when troubleshooting this type of problem. Follow the traces and repair corroded or otherwise damaged ones. (99.5% of the times this is the fix)

Oh, when troubleshooting these you WILL have to strip off the red cardboard and the black foam under the circuit board in order to follow the traces. Have fun cleaning all that crap off. Yuck.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:53:44 PM
Board: MVS MV-2
Backup RAM locations

When diagnosing the Backup RAM problems on a NEO-MVH MV-2 2-slot board:

Upper Backup RAM location: H3
Lower Backup RAM location: H4
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:53:54 PM
Model: MVS MV1FZS
Symptom: Crosshatch of Death

This board does not suffer from the same battery damage induced Crosshatch of Death as the old style 4 slot board.  The old-style 4 slot board's problem is one of legendary status and it should be documented that it is the ONLY board to consistently suffer from that kind of problem.

Powered up the board and duplicated the symptoms. Looked for obvious signs of damage and found where the bottom of the board was gouged by something. Repaired 3 broken traces connecting to the cartridge slot resolve the crosshatch problem and repaired another 3 broken traces causing corrupt video.

Always check the boards you are working on for signs of physical damage. It's pretty common on arcade boards.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:54:47 PM
Model: MVS MV-4F (newer style 4 slot)
Symptom: Z80 error and rapid audio click

Had a MV4F board that came in with a Z80 error and a rapid clicking sound in the speakers. Strange thing is that as the speakers clicked the picture on the monitor flickered.

(Little did I know this thing would kick my ass.)

Replaced the Z80 CPU to fix the Z80 error.

Now the system booted but flickered like mad. Audio ouptut was horribly distorted.

With the audio down the system worked fine except the audio output IC was getting very hot. Recapped the audio section. No help. Replaced the audio output IC. No help. Replaced the volume control. No help.

For some reason there was an oscillation happening in the audio circuit. This oscillation was causing the audio output IC to suck up large amounts of current. This was causing dropouts in the +12v output of my bench supply. These dropouts matched the screen flicker and the clicking of the speakers.

Checked every trace in the audio section - all were good. Replaced the 3 op-amps. No help. Checked all the film caps (the non-electrolytic caps)... all checked good.

All voltages looked OK but were a little lower than another MV4F board but they were within reason (+12v was a little low so the other voltages around the chip were correspondingly lower)... On a whim I removed both of the .1uf film caps on the speaker outputs. Audio was distorted but amplifier was stable.

Next I put them back in circuit one at a time. The one on the right speaker was the cause of the problem. Replaced the cap and problem was still there. It looks like there's an issue with the ground trace inside the board. Removed the cap and ran the board for an hour at 3/4 volume with no problems.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:55:19 PM
Model: MVS MV-4F
Troubleshooting reset lines

In working on a 4 slot board (MV4F) I encountered a Z80 error.

The board had other issues (documented elsewhere) and when those were fixed and the board not yet reassembled, it gave a Z80 error.

The reset line was held high.

The reset line goes through the 74AS245 IC at location E11. It goes through the latch on pins 2 and 18. If that IC is bad the reset line could be stuck high or low, causing the Z80 CPU to never boot.

That reset line must transistion from low to high to reset the Z80 CPU and make it start executing commands.

In this case the problem came because the IC at E11 was pulled from the board as a step in troubleshooting. Once the IC was placed back in the board the reset line cycled normally and the Z80 booted. (This was also tested by jumpering the reset line on pin 15 of IC A9 to pin 26 of the Z80 before replacing the IC)
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:55:30 PM
Model: MVS MV-4F
Symptom: Stuck in Watchdog (Click of Death)

Have a 4 slot board in to repair that was giving the click of death - stuck in watchdog - problem.

This can be caused by many different problems, including:

Bad CPU
Bad Work SRAM
Bad Backup SRAM
Missing control signals on Work or Backup SRAM
Shorted 74AS245 ICs buffering program ROMs on top board to CPU on bottom
Short on address bus
Short on data bus
Missing address or data signals to chips

First thing... Check for gouged traces. Found and fixed one. No effect.
Next... Substitute BIOS. Nothing.
Next... Check control signals on the Work RAM - Stuck high on pins 22 and 27.
Next... Check control signals on the Backup RAM - Stuck high on pins 22 and 27.
Next... Check control signals on the BIOS ROM - These were working.

So we had a problem somewhere in the system to where it was trying to read the BIOS but not able to initialize hardware.

Pulled the 74AS245 ICs buffering the data lines to the top board. Had no effect.

Checked for more broken traces. No more were found.

Checked the address and data lines going to the BIOS and SRAM ICs. All were good. Checked the data lines going to the NEO B1 chip. All were good. Checked the data lines. All were good.

Next checked the A22* and A23* alternate lines. Missing one one! Ran a jumper wire from Pin 55 of the NEO-E0 IC to pin 117 of the NEO-B1 IC and the board came up!

OOPS. Z80 Error. Reset line stuck high. On a Z80 since the reset line did not transition from low to high the Z80 never booted. Ran a jumper and the audio section worked. Replaced the pulled 74AS245 ICs and the board wouldnt' boot. Reset was stuck low.

Turns out the reset line for the Z80 CPU and chips on the left side of the board goes through the 74AS245 IC at E11. Removed the jumper for the reset line and board booted normally.

Plugged the top board back in, inserted some test carts and played a couple of games.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:55:42 PM
Model: MVS MV6
Symptom: Vertical lines in graphics

Some background objects had vertical lines in them - in this case the "shock Troopers, 2nd Squad" floating logo had lines. It's the logo that is on the screen when it is playing in demo mode. I traced it to connector CN8 and started tracing it on the bottom board.

UGH. It goes straight to NEO-CT0

As one final step before replacing that surface mount chip I checked the continuity between the top board and bottom. Bingo! No continuity. Next step - pull the boards apart and look at the connectors. They had something sticky on 2 of the pins and up in the socket.

Desoldered and disassembled the socket then cleaned the pins on both connectors. Reassembled, resoldered into place, and tested. Board is fixed.

Moral: Don't discount those board connections! Look at them closely to see if there is a foreign substance in there causing the problem.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:56:06 PM
Model: MVS MV4F
Symptom: Video RAM Error

This board had multiple problems due to liquid damage.

4F board came in with a Video RAM error. Replaced the upper Video RAM IC and error went away but video was glitchy and had bad colors.

Repaired a bad trace between the lower Video RAM IC and the LSPC2 IC.

Glitching was gone but the colors were bad. Test screen showed blank for red, blue for both blue and green, and white was a little off color. Put in a UniBIOS chip and noticed the green was off and the low end of red was missing AND a white block was in the place of the lowest red color. (SNK BIOS shows 4 color boxes, one for each color. The UniBIOS chip shows color spectrum bands for each color)

Checked the Color RAM and noticed that address line A2 was stuck low. Checked the NEO-B1 IC and noticed that A2 was stuck low there as well. Backtracked through the circuit and found that the TDI4 pin (pin 22 - signal name P16) was floating - no signal.

Checked the other ends of the signal - the 74LS245 IC buffering the L0 ROM and pin 134 of the LSPC2 IC. They had signals. The trace under the LSPC2 connecting to pin 134 was bad. Ran a jumper wire between the 74LS245 and the NEO-B1 chip to fix. (It was WAY easier to solder to the big pin on the 245 than the small one on the LSPC2!)

Audio was missing on one channel. Grabbed the oscilloscope and found that the volume control was bad. Replaced it with one off of a parts board.

Reassembled the game and tested. Slot 3 had vertical lines on the screen through graphics. Patched a corroded trace to fix. Played a few games to test.

Replaced the leaking battery then reassembled the board for one final test.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:56:24 PM
Model: MVS MV4F (newer smaller 4 slot)
Symptom: Missing/Garbled sound problem.

This board has been a pain to track down. The board had been worked on before  by another tech.

Fixed a broken trace on pin 15 of IC 4N (74AS245 - other tech damage - grrrrr!) and the board would play sounds but was distorted on the higher frequency digital music.

The sound ROMs are read through the YM2610 IC through data latches (74LS245) at board locations 2M and 2N. If the voice and lower frequency music notes are distorted then replace the IC at 2M. If the higher frequency music is distorted, replace the IC at 2N.

On this board the replacement of 2N did not fix it. Board had a damaged trace internal to the board and the ground pin on IC 2N was not connected. Ran a patch to fix the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:56:34 PM
Fixed: AES
Symptom: Lines in overlay graphics (text, health, etc) and no sound

Fixed a corroded trace leading to NEO-B1, pin 131, from the cartridge slot to restore the video.

Looked at the YM3016 Sound DAC and there was no serial clock or data flowing from the YM2610 sound chip. Checked the Z80 CPU and it appeared good. Looked at the clock signal on the YM2610, pin 63, and it was dead. Traced it back to a 74AS04, pin 1 near location K4 and found a corroded plate thru hole on the trace. Patched the trace to finish the board repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:57:01 PM
Fixed: AES
Symptom: Garbage on screen

Swapped out the Video RAM (62256 surface mount) chips and system would then give a yellow screen indicating a video RAM error. Checked the VRAM with a logic probe and saw that the address lines were pulsing regularly and were not pulsing erratic indicating they were being used when the system would run the Video RAM tests.  Data lines, CE*, and W* lines appeared to be working normally. Checked the pins on the LSPC2 and found address line A1 was not pulsing with data. Traced it back to the BIOS chip and found the upper pad missing from the address line A1 pin.

Ran a short jumper to fix the board.

When someone replaced the BIOS on the console with the UniBIOS chip they socketed it, but not before pulling the upper pad and platethru removing the old chip.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:57:17 PM
Fixed: AES
Symptom: No video, would play blind

Repaired bad trace on pin 126 of the NEO-B1 IC to fix the video clock and bring back the video.

Fixed a bad trace on pin 125 of the NEO-B1 IC to fix a graphics corruption problem.

Board played for about 10 minutes then rebooted to a red screen - bad Work RAM. Replaced the surface mount 62256 SRAM at R6 to bring it back from the dead. Finish the repair by running the game for a half hour to burn it in.

From the last couple of repairs it appears that the AES suffers from the same random board corrosion problems that some of the MVS boards do. Some of the boards weren't cleaned very well at the factory and gunk left on them would eat random traces.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:57:33 PM
Resurrected: AES Parts Board
Symptoms: Dead, multiple cut traces, no video out.

Had a complete parts board (no missing chips or damaged SMT chips) that was dead. Multiple solder bridges, traces cut, and missing the daughterboard.

Installed a replacement daughterboard and patched 3 cut video (RGB) traces. Patched a broken trace connecting to pin 112 of the PRO-CT0 chip. Removed multiple solder bridges. Board would then try to boot but was stuck with garbage on the screen. Shorting out 2 data lines would result in a watchdog reset. No W* or CE* activity on the video RAM but did have activity on the work RAM and the system BIOS ROM. Board was trying to boot but never making through self test enough to put a color on the screen indicating what RAM was bad.

Replaced the work RAM at R6 and the board would then boot to a blue screen with no cartridge plugged in indicating system's RAM was working properly. The video output was distorted and would fade in and out during the self test. Checked the CXA1145 RGB Encoder chip for broken traces as that chip looked to have been replaced before. Found a break between the pad and trace on Pin 13 (I REF connection.) Patched the trace to fix the video.

Board would then boot and run but had connection problems with the cartridges. The slot connectors were very loose - basically worn out. Replaced both connectors (100 pins per connector!) with ones pulled off of a parts board to fix the slot problems.

Unit had a Japanese BIOS. Swapped that out for a European BIOS and socketed it.

Board played until it got hot then would randomly reboot. Board would also reboot when tapped or flexed. Used an eraser attached to a #2 pencil to just barely touch each pin on the NEO chipset chips and found the LSPC-A0 IC was the culprit. Resoldered the IC then was able to shake and tap the board without it rebooting. Let the board play for an hour to test.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:57:51 PM
Model: MVS MV-2F
Symptom: Audio would cut in & out

Cleaned corrosion off of 2 ICs, installed an audio cap kit, and reset the backup RAM.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:58:01 PM
Model: MVS MV4
Symptom: Audio would cut in & out

Installed an audio cap kit, and reset the backup RAM.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:58:10 PM
Model: MVS MV4
Symptom: Lines in background graphics and audio would cut in & out

Swapped top board out and narrowed problem down to the bottom board. Found a gouged trace between pin 27A on connector CN9 and pin 8 of IC PRO-CT0. Patched trace to fix the graphics problem. Installed an audio cap kit and reset the backup RAM to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:58:24 PM
Model: MVS MV-4F
Symptom: Lines in background AND foreground graphics. No audio but board would make popping sounds and the screen would flicker with the pops.

Board had strange graphics corruption on foreground and background graphics. This was different than what is normally seen as evenly spaced lines (1 bad line showing up out of every 8 bits across the screen) and instead was like every other line was missing.

Swapped top board out and narrowed problem down to the bottom board. Checked the 74xx245 buffers between the top and bottom board. No problems found. Put the board under the magnifying lamp and found shorted pins from pin 65 to pin 80 (65 through 76 are ground pins anyway) on the NEO-ZMC2 IC at location 11M. Resoldered the pins to fix the graphics problem. Installed an audio cap kit and reset the backup RAM to finish the repair.

It appeared to be leftover solder from when it was factory soldered that finally bridged the trace between pin 79 and 80. There were solder blobs between every pin down that side of the chip but only 79 and 80 appeared to be shorted.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:59:12 PM
Model: MVS MV-2F
Symptom: Graphics corruption and customer requested an audio cap kit to be installed. Screen looked like line 1 was missing every odd pixel and line 2 was missing every even pixel - repeat all the way down the screen. Some graphics elements were duplicated on the screen in the middle but were garbled and shrunken horizontally. Foreground and background graphics were affected but overlay text & health bars were not. The Neo Geo splash screen was affected but the "Winners don't do drugs" screen was normal.

Board had horrible patch work done to fix some cut traces that was covered with hot glue. I removed and redid the patchwork. They missed 2 traces that needed patching and a couple of the pins were shorting together. I cut the bad part of the traces out so the gouged ends wouldn’t touch each other then resoldered in new wire patches. Resoldered the NEO-B1 and the LSPCA2 ICs to fix the graphics corruption problem and installed the audio cap kit.

The 2 slot board didn’t have any support legs under the slot sockets. I suspect the flexing of the board by inserting and removing cartridges popped the legs loose from the solder pads on the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:59:28 PM
Model: MVS MV-2F
Symptom: Calendar error

Chip tested good by substitution. Replaced crystal but oscillator would not come up. Chip was in error condition with an output that slowly cycled high-low repeatedly. Checked all inputs/outputs on the chip and they all appeared normal. Checked power to the chip with a multimeter even though the power connections showed logic "high" - the chip power was not at the proper 5.0 volt levels. Jumpered a corroded platethru to fix the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:59:41 PM
Model: MV-6 (6 slot)
Symptom: Bad Video RAM and graphics corruption

Battery leaked and caused corrosion on the board and it had a Video RAM error at $8000 - Written 5555 Read 5FFF.

Replaced and socketed both CXK5814 ICs to fix the Video RAM error. Removed the battery and cleaned up the corrosion some. The board would work but then had a funky video problem.

This wasn't a normal vertical line through the images type of problem. It looked like horizontal lines through all images. It started with overlay graphics, moved to foreground moving objects and then on to backgrounds. It also got worse as the board heated up.

Resoldered the NEO-B0, PRO-C0, and LSPC surface mount ICs. This helped some but not much.

Running a finger across the board would cause the problem to get worse if you touched the area around the 74HC32 IC at C6. Replaced that IC but it had no effect.

Broke out the component cooler and sprayed the PC board under each chip around the 74HC32 and found that the clock driver IC, a 74LS368 was bad. Spraying it with component cooler immediately fixed the graphics problems until the chip heated up again.

Replaced the chip and played a game of Shock Troopers 2nd Squad.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 08:59:52 PM
Model: MVS MV2 (older 2 slot)
Symptom: Lines in foreground (player) AND background objects

On the 2 slot Neo Geo boards the NEO-257 ICs are the 2 to 1 multiplexer ICs that choose which slot to get the graphics data from. There are 3 of them on the board. If one of these is bad then there will be lines in the graphics elements they are selecting. Top left is background graphics, bottom left is player graphics, and the one on the right side is for text and other overlaid objects.

Replaced both of the left side NEO-257 ICs and the corruption was still there. Logic probe showed that the data was coming in and exiting the NEO-257 ICs correctly but I thought that maybe they were garbling the data. Nope. Problem still there.

Did some further tracing down to where the data goes to the NEO-C0 chip. It flows from the 257s through the ZMC2 IC and then on to the C0 chip.

Replaced the NEO-ZMC2 IC and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:00:29 PM
Board: MVS MV4
Symptom: Click of Death

Board was stuck in watchdog reset and had battery corrosion damage. Board already had wire jumpers already on it to fix a crosshatch of death problem.

Cleaned the corrosion as best possible. Checked the control lines on the Backup RAM and Work RAM. They were stuck high meaning the chips weren't being accessed. Checked the enable line (pin 20) on the BIOS and it was stuck high. There was a problem in the decode or read/write circuitry. Checked around the chips near the battery for traces eaten by corrosion. Found pin 9 on the 74LS05 at location D11 had a bad trace connecting to pin 5 of the 74LS259 at location C5. Ran a jumper to fix the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:00:39 PM
Model: MVS MV4
Symptom: lines in graphics and sound problems on top board

Swapped top boards out to narrow problem to the top board. Lines in the graphics were NOT the same for all 4 slots. Slot 4 was perfect. Slot 3 had 2 repeating vertical lines. Slot 2 had a single repeating vertical line. Slot 1 had every other vertical line missing. All slots had the same sound problems: missing tunes, incorrect tunes, and garbled sound effects.

Found 3 bad traces in the sound circuitry between the board connector CN11 and the buffer/latch chips. Fixed at trace between pin 4 of R6, L6, G6, and C6 and pin 5A of CN11. Fixed a trace between 6B of CN11 and pin 3 of S6, M6, H6, and D6. Fixed a trace between 12B of CN11 and pin 9 of S6, M6, H6, and D6. Tested all 4 slots and sound was working fine.

Checked slot 3 and found 2 bad traces in the area between the slot and the 4 to 1 data selector IC (74F253) at A7 and at B7. Ran a jumper from pin 4 of A7 to cartridge connector CTRG5, pin 33A and a jumper from pin 4 of B7 to CTRG5, pin 34A to fix the graphics problem on slot 3.

Checked slot 2 and found a nasty looking signal on pin 11 of the 4 to 1 data selector IC at C1 (74F253). Checked continuity to pin 20B of CTRG3 and found it good. Looked closely at the pin on the cartridge slot and found slight corrosion. Cleaned the pin and the slot tested good.

Slot 1 had a bad trace between pin 46 of CTRG1 and pin 10 of P7 (74F253). Jumpered the trace and tested the slot.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:00:50 PM
Model: MV2
Symptom: Backup RAM Error

Board would get to the green screen then reboot. This was a constant repeating cycle. Flipped all the dip switches to run the system through a Backup RAM test. It gave a Backup RAM error with the message Written: 5555 Read: B240

(The B240 error is stuff of legend over on the Neo-Geo.com forums.)

Checked the Backup RAM with a logic probe and found pin 20 (CS*) was dead on both. Traced it back to the 74HC32 and back to the battery backup circuit. Traces were good. The resistors and diodes in that section were good. Checked the C1815 transistor with an ohmmeter and it was OPEN from collector to emitter. Replaced the transistor and the board booted right up.

I have to say this is the first time I've seen an open transistor that wasn't blown in pieces. I think the corrosion from the battery must've traveled up the legs and into the body of the transistor and caused it.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:01:06 PM
Model: MV2F
Symptom: Missing audio from right channel after 5 minutes

This board was traded in as a "dead" board purchased off of eBay towards the repair of another board. Found 1 penny in the bottom of the box and found another two pennies and a dime wedged in the memory card slot. Removed the coins, straightened the pins and tested the board. Fixed the audio problem by recapping the audio section.

Replaced the memory card connector with one from a parts board to finish the repair. The original 2 slot arcade cabinet is set up to where the player can insert a memory card to save games. Apparently someone shoved coins in this slot.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:01:17 PM
Model MV4FT2 (The 3rd, newest, and smallest verison of the 4 slot)
Symptom: Carts would not work in slots 1 and 2. No audio.

Strange thing was that you could put carts in 3 or 4... or 3 and 4 and it would work. Put a cart in slot 2 or slot 1 and you would get a crosshatch. Put a cart in 2, 3, and 4 then all three slots were usable. Put carts in all slots and the board would constantly reboot after doing self tests.

Repaired a bad trace between Slot 1 and 2, pin 13B on the program board connector and IC 1A, a NEO-244, pin 38. This was the program data line D8. Now all four slots would run cartridges.

The audio problem was tough to track down. The audio test worked so the bottom board was at least generating audio from the diagnostics.

Swapped the NEO-244 IC at A2. Nothing. Traced down all the connections between the slots and the NEO chips and then the NEO chips to the CN9 connector. Then traced it from the CN9 connector on the bottom board back through the 74xx logic to the 2610 Yamaha chip. Everything tested good.

Frustrated, I cleared the backup RAM and the sound magically returned. AAAAAAAAAAAAAHHHHHH!!!!!
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:01:28 PM
Model: MV1
Symptom: Backup RAM Error

Board was giving Backup RAM Error: Written 5555 Read 7255

Battery leaked on the board. Checked the traces to the Backup RAM. They tested good. Removed the battery, cleaned the corrosion, patched 2 bad traces from the NEO-F0 IC to the DIP switches, and replaced the Backup RAM at H6.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:01:40 PM
Model: MV1
Troubleshooting RAM Problems

When troubleshooting RAM Problems on the MV1 the error message (Read 7255) can be broken down into upper bits (72) and lower bits (55)

The bits are kept in RAM as follows:

Backup RAM: Upper H6, Lower H5
Work RAM: Upper G3, Lower G4

The rest of the ICs will get filled in as I troubleshoot other boards.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:01:51 PM
Model: MV1C
Symptom: No video sync

Board had no video sync. There is a 470 ohm SMT resistor tying the sync line high then a 100 ohm SMT resistor inline with a 74HC32 surface mount IC. The IC had inputs but the output was stuck high. Replaced the IC and the 100 ohm surface mount resistor.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:02:05 PM
Model: MVS - MV2F
Symptom: Lines in player graphics and some background graphics for slot 2.

Logic probe showed pin 20 on the ZMC2 chip stuck high when a cart was being accessed in slot 2. Checked pin 9 on the NEO-257 at H/J2 and it was stuck high. Checked pin 16 and it had garbage for the inputs. Checked the trace from the NEO-257 to the slot and it was good. Replaced the NEO-257 IC to fix the board as its inputs were damaged.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:02:14 PM
Model: Bootleg MV1C
Symptom: Plays for a couple of minutes then starts glitching

Board would get horizontal streaks on the display. Would get worse as game was played. Pushing on the SMT chips had no effect. Power cycled game and it worked again but played slower and the sounds were played slower as well then started streaking more and more until it lost sync and died. Resoldered the main video IC and system clock driver IC to no effect. No clock signal was coming from the 24MHz crystal. Checked the 1M and 100 ohm resistors and the 2 caps connected to the crystal. Checked soldering on the system clock driver IC. All checked good. Replaced the crystal and played a few games.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:02:24 PM
Model: Bootleg MV1C
Symptom: Missing BIOS.

Burned a replacement BIOS ROM. Board booted and played but had no sound. Replaced missing sound pot and fixed a bad trace.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:02:37 PM
Model: MV-1F
Symptom: Requires separate coin mechs for player 1 and player 2.

Unit had a 2 slot BIOS in it. (usa_2slt.bin) Replaced it with the standard USA BIOS (neo-geo.rom image) and played a couple of games to test.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:02:48 PM
Model: MV4FS
Symptom: Dead. Had a note taped to it that there were lines in the graphics.

Unit was missing the BIOS chip. Programmed a replacement chip (27C1024) and booted it. It had lines in the graphics and was missing sounds. Board had been repaired before and had many chips replaced on upper and lower boards.  It also had a dark liquid spill on the top board.

Checked all the previous trace repairs. Reset the Backup RAM to fix the sound issue. Cleaned the top board and the slot connectors to fix the lines in the graphics. Reassembled the board and replaced all the missing standoffs, screws, and mounting feet.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:03:00 PM
Model: MV4
Symptom: Dead. Click of death.

Bottom board had severe corrosion damage on the platethru holes and was beyond economical repair. Contacted customer and swapped out the bottom board with one that was already repaired. Slot 1, 2, and 3 had lines through the graphics and if a cart in slot 1 was bumped the board would reset. Cleaned the top boad and slots thoroughly to fix slots 2/3. Replaced the slot 1 connectors with ones pulled from a parts board to finish the repair. (No new ones are available.)

Customer reported the boardset was 300 feet from the ocean at an arcade which would explain the corrosion damage.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:03:19 PM
Model: MVS MV-4
Symptom: Multiple - Backup RAM Error $D000, Calendar Error, audio, and slot problems

Purchased a 4 slot board to refurb and resell. It was sold as having a "RAM Error"

The board had a Backup RAM Error at $D000, Written 5555, Read 55F8. Since it was at the zero address boundary I checked the enable lines and the R/W line first. The R/W line was dead on the lower Backup RAM chip. Soldered in a 30ga kynar jumper between pin 8 of the 74HC32 IC at D8 and pin 27 of the Backup RAM at locaiton K8.

The board now booted but was stuck at the green screen - a calendar chip problem. The logic probe showed normal signals on all the pins of the 4990 IC but gave strange readings on the crystal. Checked the crystal with an oscilloscope. It was dead. Checked the traces around the crystal and found the trace from pin 13 on the 4990 IC was bad. Soldered in a kynar jumper and the board booted to the crosshatch.

Ran the board through tests and found the left audio channel was dead. Installed a cap kit to fix the audio problems.

Board would boot but not recognize cartridges. Isolated this to the top board. Checked the board thoroughly and found that the slots were dirty. Cleaned the board and slots then ran the board through a final set of tests in preparation for resale.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:03:29 PM
Model: MV-4
Symptom: Crosshatch of death (wouldn't recognize cartridges)

Checked the traces under the battery and found the 3rd trace bad. Jumpered the first 4 traces as they were discolored and would eventually go bad. Installed a new battery and tested the system.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:03:37 PM
Model: MV1
Symtpom: Audio cuts out

The audio would get very low and sputtery sounding at intermittent times. Board had a cap kit already installed. Narrowed it down to a dirty Stereo/Mono selector switch. Cleaned the Stereo/Mono selector switch and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:03:45 PM
Model: MV4
Symptom: Video RAM error

Board gave a Video RAM Error. Address 00000E17, Write 5555, Read 5557

Replaced the surface mount video RAM IC at K9. Reset the Clock/Calendar, replaced 2 missing screws, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:03:54 PM
Model: MV4
Symptom: Z80 Error

Replaced the Z80 chip with a Z80A. Game would then boot but had no audio. Installed an audio cap kit to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:04:04 PM
Model: AES
Tip: Diagnosing RAM problems

The AES is different than the MVS in that it does not display error messages on the screen if there are hardware problems. To diagnose problems, boot the system without a cartridge installed. The screen will turn different colors depending on the errors.

Blue = All tests passed
Red = WorkRAM error ($100000 region)
Green = PaletteRAM error ($400000 region)
Yellow = VideoRAM error
Pink = Bios selfcheck error ($C00000 region)
Cyan = Memory card error

The AES tests will only test the memory card if it is inserted and it is blank. It does NOT test the Z80 or other parts of the sound subsystem.

Many thanks to the folks at the neo-geo.com forums for this list!
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:04:13 PM
Model: MVS-2F
Symptom: Calendar Error message and Battery acid damage

Removed Battery and cleaned the acid damage. Repaired 1 broken trace to fix the calendar problem.

Board would boot and run but had no audio and lines on slot 2 that would come and go if the cartridge was wiggled. Cleaned slots and whole board thoroughly then installed an audio cap kit and a new battery.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:04:21 PM
Model: MV1C
Symptom: Dead

MV1C arrived missing fuse. Replaced fuse and board was dead. Would come up with a white screen with 4 colored blocks. Cleaned board and inspected for damage. Resistor R79 (100 ohms) was broken off the bottom of the board. Replaced it with one from a parts board. Still dead.

Inspected the board further and found pin 40 (Vcc) was broken off of the BIOS ROM. Jumpered the pin to the body with a multimeter probe and the board booted to Work RAM test. Replaced the BIOS ROM with one from a parts board and set all jumpers to off. Board would boot but get stuck on a green screen.

Checked the clock/calendar crystal. It was dead. Replaced it and played a few games to test the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:04:30 PM
Model: AES
Symptom: Needed custom BIOS installed

Customer wanted the system upgraded. It had the old Debug BIOS stacked on top of the AES BIOS chip.

Removed 1 resistor and the double stacked chips. Installed a new socket and a freshly programmed UniBIOS chip. Board would not boot. The UniBIOS file supplied by the customer was corrupt.

Programmed another EPROM with the UniBIOS 2.3 code and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:04:39 PM
Model: MV1C
Symptom: Backup RAM Errors

Backup RAM Error: Written: 5555 Read 5540

Found a broken trace between RAM 2 and RAM 4 on pin 20. Jumpered pin 20 from RAM 2 to pin 10 on U3 (74HC32.) Board then booted to:

Backup RAM Error: Written: 5555 Read 558E

Found an erratic signal on the R/W line (pin 27) of RAM 2. Jumpered pin 27 from RAM 2 to pin 6 on U3 (74HC32.) Cleaned the board and played a few games.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:04:48 PM
Model: MV4FT2
Symptom: Click of Death

Board was stuck with a click of death problem. Swapped BIOS chips, still dead. Checked the address and data lines. All 16 data lines were stuck high. Used the "well calibrated finger" and found that the IC at location N3 (74AS245) connecting the CPU to the sound subsystem was shorted internally and getting very hot. Pulled the IC and tested it. It was bad, but replacing it did not free up the data lines.

Pulled the 2 74AS245 latches at C11 and D11 connecting the CPU data lines to the cartridge program ROM data lines. When tested they were found to be bad. Replaced them and system then booted up to a Video RAM error at 8000, written 5555 read 0000. Replaced both SRAM ICs to finish up the repair and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:04:58 PM
Model: MV2F
Symptom: Locks up at boot

When running a cartridge with the "Winners Don't Do Drugs" screen, it would show the Neo Geo splash screen then the Winners screen before locking up.

Installed a UniBIOS chip and retrieved the crash info. The developer of the UniBIOS chip said the game was crashing within code.

Ran extended Work RAM tests (turn on all DIP switches) but found no errors. Ran CRC tests on the cartridges and found that none of the carts gave good CRC checks in this board.

Used a logic probe and verified that all of the program ROM data lines and address lines were active. Found that address line A18 was dead. The trace was good between slot 1 and slot 2 but not between the slots and the NEO-E0 chip, pin 40, and board location G3. Ran a jumper to fix the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:05:06 PM
Model: MV4
Symptom: Audio cuts in & out, memory backup not working

Board had been worked on before for an audio problem and had incorrect caps installed. Installed a cap kit and jumpered a damaged trace.

Replaced the backup battery then installed 2 missing hex standoffs and mounting feet. Replaced 2 broken mounting feet.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:05:15 PM
Model: MV4
Symtpom: Audio cuts in & out

Installed an audio cap kit and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:05:27 PM
Model: MV4
Symptom: Dead - no click of death

Board fired up to a blank screen. No garbage on screen and no click of death. Power cycled the board a couple of times and it came up with a Work RAM error but no diagnostic info such as at what address or what was written/read.

Replaced the work SRAM IC at location D9 and tested board. No audio.

Installed an audio cap kit to finish the repair and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:06:23 PM
Model: AES
Symptom: No sound

This was a bear to track down. Cleaned corrosion off the board. Cleaned the right end pins on each slot and socketed 3 chips to check the traces under them. Found a bad trace between E9 pin 6 (74LS11) and CN4 (front slot) pin 47A and Q3 pin 9 (74LS04). This trace was the Chip Enable pin on the sound program ROM. Patched the trace and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:06:32 PM
Model: Ikari III - The Rescue
Symptom: Garbled graphics a lines on the screen

Checked the board for damaged traces then started checking the video SRAM with the well calibrated finger. Found one (and received a blister on the finger) that was internally shorted. Found another one hotter than the others and checked it with a logic probe. It had bad looking signals on the data lines. Replaced both SRAM ICs and tested the game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:06:40 PM
Model: MV1
Symptom: Z80 Error

Swapped the Z80 chip with the proper Z80A. No change. Inspected the board closely and found some corrosion on 4 pins of a surface mount IC connected to the Z80 CPU. Continuity tests showed one trace was open. Cleaned the board and soldered in Kynar jumpers pm all 4 corroded traces to repair it.

Only one was needed to do the repair but by doing all 4 the board will last a lot longer for the customer.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:06:49 PM
Model: MV2F
Symptom: Vertical lines in backgrounds

Pin 16 (D3 for Slot 2) on the NE0-257 IC at J2 was shorted to ground. Removed the IC and checked the trace on the board. The short was gone and was internal to the chip. Replaced the chip and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:06:56 PM
Model: MV4
Symptom: Slot 1 dead. Missing left channel on audio.

Checked the address lines and data lines on the Program ROMs for slot one. Found pin 15A on CTRG2 connector for slot 1 had a bad trace between it and C3 pin 7 (74LS245 IC). Patched the trace and tested the board.

Installed an audio cap kit to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:07:04 PM
Tip: Cartridge ROMs

When troubleshooting cartridge issues it helps to know which ROM does what.

P ROM - 68K program (16-bit)
V1 ROM - ADPCM-A port (8-bit)   <-- Music & sound samples
V2 ROM - ADPCM-B port (8-bit)   <-- Music & sound samples

C ROM - VDP object tiles (32-bit)
S ROM - VDP overlay tiles (8-bit)
M ROM - Z80 program (8-bit)   <-- Sound Program ROM
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:07:13 PM
Model: MV4
Symptom: No audio from any slot or from self test

Installed an audio cap kit and the board would play the self test sounds but had no audio from carts. Replaced 1 74245 IC at location R1 on the lower board. The board would then play music and partial sound from carts. The Z80 CPU would lock up at set places on game cartridges when certain sounds were to be played.

Isolated the problem to the top board. Checked the ADPCM ROM address/data/control lines. They were perfect. Checked the sound program ROM. Pin 3 was stuck low. Replaced a shorted 74LS244 at location N5 on the top board to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:07:21 PM
Model: MV4
Symptom: Z80 ERROR

Replaced the Z80 CPU and tested
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:07:31 PM
Model: MV4
Symptom Backup RAM Error

Backup RAM Error: Address D0814 Written 5555 Read 55D5. Replaced bad Backup RAM chip at D9. Board then came up with a Video RAM Error: Address 00803 Written AAAA Read ADAA. Replaced the Video SRAM IC at location L9.

Board came up but had very faint audio output. Installed an audio cap kit to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:08:03 PM
Model: MV4
Symptom: "Z80 Error and sound failing"

Could not duplicate a Z80 error. The board immediately powered up with a Work RAM Error: Address: 00100008 Written AAAA Read AAA2.

Replaced a bad surface mount RAM at G9. Tested audio levels in the hardware test menu. Right channel was barely audible and left was not audible at all. Installed cap kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:08:18 PM
Model: MV1FS
Symptom: Stuck on Green - Calendar Error

Board had damage from a leaking battery. Customer removed battery before sending the board in.

Cleaned the board and jumpered a bad trace to fix the calendar problem. Board was stuck in a reboot cycle. Repaired another dead trace in the battery section that was sending power to a 74HC32 as part of the circuit for the enable lines on the Backup RAM. Replaced the missing battery and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:08:32 PM
Model: MV4
Symptom: Stuck on Crosshatch

User attempted repair damage. Tried a battery swap and board would no longer recognize any cartridge installed.

Found a knife scrape on the bottom board. Repaired 1 bad trace and jumpered another bad trace. Replaced 2 stripped screws.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:08:49 PM
Model: MV2F
Symptom: Z80 Error

Replaced a bad Z80 chip and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:09:00 PM
Model: MV4FT2
Symptom: Audio would cut in & out.

The interconnect between the top and bottom boards that carries the signals to/from the Audio ROMs was broken on the bottom board side. Replaced the connector, installed a cap kit and a new battery, then tested the game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:09:08 PM
Model: MV4
Symptom: No audio. Would not keep settings in memory.

Battery read 7mv instead of 3.6v. Ran the game for an hour and the battery took no charge. Installed an audio cap kit and a new battery.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:09:22 PM
Model: Street Smart
Symtpom: Dead

Replaced missing 6264 SRAM IC, fixed a short on the ROM board connector CN1 and resoldered it. Set the DIP switches and tested game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:09:32 PM
Model: Street Smart
Symtpom: Dead

Fixed bent pins on the audio output IC. The 12v line was shorted to ground and causing the switching power supply to go into shutdown.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:09:41 PM
Model: Neo Geo AES
Symptom: Red screen with no cartridge installed

This symptom is indicative of bad Work RAM. Checked the board and found that several of the memory lines on both Work SRAM chips had been partially desoldered and that there was some chemical corrosion on the pads. There was also one existing repaired trace and several data line traces that had their coating scraped badly. Cleaned the pads up, resoldered the data lines, and checked continuity to the CPU. Patched one bad data line and coated the bare traces to protect them. Tested the game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:10:09 PM
Model: MV4
Symptom: Click of death

Battery leaked on the board and ate many traces. Cleaned both the top and bottom boards. Attempted repair on the bottom board but it was uneconomical to repair.

Swapped out the bottom board for one that was already repaired. Game then worked but Slot 4 had corrupt graphics. Repaired two traces on the top board to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:10:29 PM
Model: MV4
Symptom: Low audio and garbled sounds

Installed an audio cap kit to restore sound and noticed that the sound effects and music were all mixed up. Generally this problem is caused by a bad IC at F1, F2, G1, or G2. Replaced those to no effect. Swapped out the SRAM and Z80 IC to no effect.

After the board sat overnight it would play the audio test tones in the hardware tests as garbled sounds when cold. This is a problem with the digital sound circuit and not a problem with the bottom board interfacing with the top board. Replaced a bad YM2610 IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:10:41 PM
Model: MV4
Symptom: Low audio and missing sounds

Installed an audio cap kit to restore sound and noticed that the sound effects for spelling the bonus word in Shock Troopers, 2nd Squad was missing. In Metal Slug the bonus sound from picking up fruit or other non-gun objects was missing.

Replaced a bad YM2610 IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:10:56 PM
Tip: Neo-Geo Cartridge ROM Functions:

P: Program ROMs

P1 is typically the main program ROM, it can be up to 8M and contains the entire game logic.

Some old PROG boards use 2/4M ROMs so P2-4 can be the rest of the P1 address space.

Then there's another address range used for a few different things such as the link circuitry, Fatal Fury 2 protection and later on it became used for another 8M+ of program ROM. ROMs mapped here are SP2 (P2 on the chip) if P1 is 8M.

EP1 replaces P1 with updated program code.

EP2 can be either the second half of EP1 if they're both 4M or can be the same thing as SP2 (8M+).

V are YM2610 ADPCM data ROMs.

There are actually two types of V ROM, one for the low frequency channel, one for the high. Games quickly started containing a chip called NEO-PCM which allows both channels to use the same ROM.

C ROMs only contain sprite data (which also makes up the backgrounds on the Neo), not the fixed tile layer data.

M ROM contains the Z80 sound engine program as well as the actual "track" sequences. Remember all sample data however is contained in the V ROMs.

S aka the "FIX" layer ROM contains the fixed (non-scrollable) tilemap layer that overlays sprites. Life/POW bars are made of this.

Thanks to Calpis on the Assemblergames.com forum for this info!
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:12:50 PM
Model: MV4
Symptom: RAM Error, written AAAA read A8AA

Board was shipped in a box that didn't allow for sufficient packing. 2 standoffs and the top cover were bent.

Replaced 1 bad SRAM IC at location H9, installed an audio cap kit, replaced 2 bent standoffs, and fixed the bent top cover. The audio is now loud and crisp.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:12:58 PM
Model: MV4
Symptom: Stuck in watchdog. Customer requested a UniBIOS upgrade and a new battery be installed.

Repaired 3 broken traces. Tested board and found the audio level was low. Recapped the board to fix the audio problem. Replaced the battery and upgraded the system with a UniBIOS 3.0 chip.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:13:07 PM
Model: MV4
Symptom: Backup RAM Error

Replaced bad surface mount SRAM IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:13:19 PM
Model: MV4
Symptom: Backup RAM Error (Written 5555, Read D555)

Replaced bad Backup RAM chip and tested board. Other Backup RAM chip was bad too. Replaced other Backup RAM chip and tested. No audio. Installed an audio cap kit and tested board. Replaced 3 missing screws holding the top cover on and inspected the top board for damage.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:13:27 PM
Model: MV1
Symptom: Sound dies after board is powered on for about 30 seconds

Cleaned the Stereo/Mono audio selector switch and tested board. Customer requested an audio cap kit be installed.

Installed the audio cap kit and tested board. Battery had started leaking. Contacted customer and replaced it per his request. Reset the Backup RAM and set the system date/time. Played a couple of games to test.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:13:35 PM
Model: MV1
Symptom: No Audio

The Stereo/Mono switch was physically broken off the board. Jumpered the switch to put the board into stereo mode then recapped the audio section. Replace the leaking memory backup battery. Reset the Backup RAM, set the date/time, and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:13:42 PM
Model: MV1
Symptom: Stuck on green

Checked pin 14 for +5v when board was powered up. It was there. Checked the 32.768KHz clock crystal and found it was dead. Replaced the crystal and played a game to test the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:13:51 PM
Model: MV1FS
Symptom: Garbled audio

The audio wasn't muffled but rather was garbled in the digital section of the board. Soldered over several scratched traces to protect them and checked the DAC and looping Op-Amp IC connected to the DAC. Found the battery had leaked. Cleaned the board, resoldered 2 corroded plate thru to trace connections to fix the audio, and replaced the battery.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:14:00 PM
Model: MV2F
Symptom: COLOR RAM ERROR Written 5555 Read 5755

Board came in with severe attempted repair damage. Removed both Color RAMs (4364/6264) and checked for damaged traces. Repaired 7 damaged traces and socketed the 2 Color RAMs. The Color RAMs tested good. Data 1 line on the Color RAM furthest away from the JAMMA connector had runaway pulses on pin 12.

Removed the 74LS273 at location A8 and this did not affect the error message. Replaced the NEO-G0 custom IC at location B9 to repair the board. Testing the board revealed that P1 Up did not work. Repaired a corroded trace at the JAMMA connector to finish the board repair and tested.

The memory backup battery had started leaking. Contacted the customer concerning the leaking battery and replaced it per his request.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:14:12 PM
Model: MV2F
Tip: Troubleshooting Color RAM Errors

When troubleshooting Color RAM Error messages it's important to take the proper steps to quickly isolate the problems.

If the error message isn't at the beginning of the bank then one of the SRAM chips is bad. The first 2 characters of the READ string is handled by one chip and the last 2 characters by the other. In other words:

Written 5555 Read 5755 means the chip furthest from the JAMMA connector is bad.
Written 5555 Read 5557 means the one closest to the JAMMA connector is bad.

Replace the chip and test.

If the error is at the beginning edge of the bank, follow the steps above and replace the appropriate Color RAM chip. If that does NOT fix the problem then more in depth troubleshooting is needed.

First step is to check for damaged traces and repair them as necessary.

Next, carefully examine the output resistor ladders for damaged resistors. If these are found, the problem will most likely be a bad or damaged 74LS273 IC causing the Color RAM Error messages.

If the resistor ladder components are OK then check signals on the Color RAM with a logic probe. If signals are stuck low or high, check for shorts to ground. If the lines are not shorted then remove and test the Color RAM chips and 74LS273 ICs. If the lines are still stuck low then the problem will be with the NEO-G0 IC as it's the only component left to check.

If the signals are racing on the affected data pin when checked with the logic probe then do the same thing: Remove and test the Color RAM chips and the 74LS273 IC connected to the racing data line. If the line is still racing with those removed then replace the NEO-G0 chip.

Enjoy!
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:14:23 PM
Model: All
Tip: Checking the NiCd Battery for leakage

One funny thing about NiCd batteries are that they leak after they go bad. This isn't a normal kind of leakage you would expect from a battery but is rather a crystalline growth that appears on the terminals and spreads across the board and follows traces. This will eventually turn a telltale blue but when first starting out looks like simple dust.

Do not let this dust fool you!

When the battery starts to leak it must be replaced ASAP as the leakage will only get worse. This will eat traces and component leads. It will ruin sockets, chips, resistors, capacitors, and more. It doesn't care if the board is a common cheapie or a rare expensive one. It will leak just the same.

Here are 2 pics of the same battery. One is the shot of the positive terminal and the other of the negative. In one picture the solder joint is nice and shiny - a good looking solder joint. In the other you can see the growth on the battery and how it has already affected the solder joint. That isn't a cold solder joint but rather one that has been chemically corroded by the leakage from the battery.

When replacing these old NiCd batteries it is OK to use NiMH types with the same form factor. It is also OK to replace them with a battery having a higher milliamp hour rating such as replacing a 50maH with a 70maH rated battery.

Good luck, and replace those batteries before they ruin the game!
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:14:32 PM
Model: MV4
Symptom: Corrupt Graphics

Repaired 7 broken traces and tested. The board had poor audio and a leaking battery. Replaced the battery and recapped the board to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:14:40 PM
Model: MV4
Symptom: RAM ERROR at location $8000

Replaced 2 bad CXK5814 SRAM Ics and tested board. Audio levels were low and the battery was leaking. Replaced the battery, recapped the audio section, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:14:49 PM
Model: MV1C
Symptom: Video RAM Error

Replaced 2 62256 surface mount SRAM chips and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:14:58 PM
Model: MV6
Symptom: Missing Audio on slots 4 through 6

Jumpered a bad trace between pin 1 on IC B13 and pin of B17. Tested Game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:15:10 PM
Model: MV6
Symptom: Slots 4 and 5 dead

Slots 4 and 5 would show crosshatch when a known good cartridge was installed. Cleaned the slots aggressively with very fine emery cloth as the slots had bad corrosion problems due to liquid (possibly rodent) damage.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:15:24 PM
Model: MV6
Symptom: Missing video on odd numbered slots

Games would play fine in the even numbered slots. The odd numbered slots had audio, but missing video - foreground, background, and text were all missing. Repaired bad trace between D3 pin 11 and C29 pin 15. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:15:40 PM
Model: MV1FT
Symptom: Dead. Garbage on screen

Straightened a bent pin on the BIOS ROM, powered up the game, and received a SYSTEM ROM ERROR message. Programmed a new BIOS ROM, booted the system, and received a Z80 ERROR message. Replaced the Z80 CPU and tested. Splash screen sound was normal, but the games sounds were horribly mangled. Repaired a damaged trace to finish the repair and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:15:53 PM
Model: MV4
Symptom: Z80 ERROR

Address line A16 on the sound subsystem was racing. Replaced the most common problem chips first: CPU, SRAM, and the 74LS244, but the problem remained. Replaced the SM1 ROM IC to fix the error. Installed a cap kit to fix low audio issues and cleaned the slots to fix cartridge issues.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:16:09 PM
Model: All MVS
Tip: BIOS Identification

Here's a tip from a former SNK employee:

Power up the MVS board without a cartridge installed. Look at the border color around the edge of the crosshatch screen. The color will reflect the region the BIOS is for.

Green: 6 slot, an older BIOS
Light Blue: USA BIOS, labeled SPU2
Dark Blue: Spanish BIOS, labeled SPS2
Red: Japanese BIOS, labeled SPJ2
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:16:17 PM
Model: MV2
Symptom: Calendar Error

Inspection of the board turned up gouged traces in several different spots. Removed 2 shorts and patched 9 broken traces. Tested game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:16:34 PM
Model: Aero Fighters 3 - MVS cartridge
Symptom: Dead

Board was a converted cartridge. When cart was placed in system, the system would exhibit the click of death symptoms. Installed a missing jumper for the CE* signal for the Program ROM and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:16:43 PM
Model: MV2F
Symptom: Video RAM Error

Video RAM Error $8000 Written 5555 Read 0000

Replaced 2 bad CXK-5814 SRAM chips and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:16:54 PM
Model: MV4
Symptom: Very low audio. Missing audio on slot 4

Recapped audio section to fix low audio issues. Replaced a bad 74LS244 on the top board to fix the missing audio on slot 4. Installed a new battery per owner's request.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:17:06 PM
Model: MV6
Symptom: Slot 1 not working

Repaired 3 burned traces on the top board and tested. It appears the board was powered up wet since the traces that were burned were once that are grounded and next to the power pin on 3 of the 74LS244 ICs.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:17:19 PM
Model: MV4FT2
Symptom: Graphic corruption, battery corrosion damage

Re-mounted the battery to the top side of the bottom board, jumpered 3 corroded traces on the bottom board, sealed up 8 scraped traces on the bottom of the bottom board, then cleaned the top board & slots. Removed a bent pin from slot 2, fixed the bad soldering on a user installed RCA jack connecting a pause button, and replaced 2 missing screws. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:17:51 PM
Model: MV4FT2
Tip: Battery corrosion damage

When the battery leaks on the MV4FT2 version of the Neo Geo 4 slot, there are 3 traces that run next to the battery area that control the graphics on the slots that can be affected by the corrosion damage. If this happens, the graphics will come and go, especially when touching pin 56 of the NEO-253 chip at D5 on the top board with a logic probe or oscilloscope probe.

The trace from this pin routes to the bottom board and is one of the three traces that run next to the battery area on the top side of the bottom board. These three traces will most likely be damaged and require jumpering with 30ga Kynar wire.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:17:59 PM
Model: MV2
Symptom: Graphic corruption

Board had rodent damage on one of the NEO-257 ICs. Cleaned the board and slots then replaced a leaking battery. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:18:17 PM
Model: MV2F
Symptoms: Vertical lines on both slots

Board had a leaking battery. Cleaned up the battery corrosion and jumpered 2 traces between the NEO-257 and the NEO-ZMC2 ICs to fix slot 1. Jumpered a bad trace between slot 2 and the NEO-257 IC to fix slot 2. Installed a new battery and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:18:26 PM
Model: MV4
Symptom: Low audio, replace battery

Customer requested battery change. Installed cap kit and battery. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:18:33 PM
Model: MV2F
Symptom: Low audio on one channel and lines on screen

Battery was leaking. Removed battery, cleaned board, and installed cap kit to fix audio issue. Replaced bad NEO-257 IC to fix lines on screen. Installed new battery and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:18:43 PM
Model: MV1
Symptom: Backup RAM Error

Board had a Backup RAM Error at D0000, Written 0000, Read 04D0. Replaced bad 74HC32 chip controlling the enable lines. Board then gave a Backup RAM error at D0008. Replaced one 62256 SRAM chip and tested. Board had no audio. Replaced 2 physically broken 470uf @ 16v caps to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:18:58 PM
Model: MV4
Symptom: Work RAM Error

Replaced bad SRAM at location G9 and ran self tests. Audio level was low. Installed audio cap kit and tested. Board would not read any carts. Replaced a corroded 74LS244 on the top board, cleaned the rodent damage, and patched 2 traces. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:19:12 PM
Model: MV1
Symptom: Work RAM Error: Written AAAA Read: AA2A

Replaced the SRAM at location H3 and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:19:20 PM
Model: MV6
Symptom: No Audio

Board had very faint audio when running hardware test. Recapped board and tested. Board had strong audio in test mode but no audio for games. Reset backup RAM and tested. Corrupt backup RAM was causing the audio to not work.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:19:29 PM
Model: MV4
Symptom: Very low audio

Installed audio cap kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:19:37 PM
Model: MV4
Symptom: Low Audio

Installed Cap Kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:19:45 PM
Model: MV4
Symptom: Low Audio

Board would not play hardware test tones. Game audio worked, but was low. Installed cap kit to fix audio levels. Replaced bad SM1 ROM to fix the hardware test tones.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:19:53 PM
Model: MV4
Symptom: Crosshatch of death

Removed leaking battery and cleaned board. Repaired 12 bad traces and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:20:02 PM
Model: MV1
Symptom: Tinny sounding audio

Cleaned the stereo/mono switch and replaced a bad battery that had started to leak. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:20:12 PM
Model: MV1
Symptom: Stuck on Green

Board had the battery already removed and had minimal corrosion damage but still had the crystal and D4990 clock chip with some on it. Cleaned the corrosion, including some bridging the crystal's leads and tested the board. The corrosion bridge caused the crystal to not oscillate. Replaced the missing battery and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:20:23 PM
Model: MV1
Symptom: Z80 Error

Board was labeled Z80 error but had multiple issues caused by battery leakage, attempted repairs, and rodent damage. Removed an extra Z80 CPU from the BIOS socket and installed the correct BIOS chip. Removed leaking battery, cleaned board, and replaced crystal to fix calendar error. Patched a bad trace going to the cartridge port. Z80 Error had 2 causes. The first was a corroded trace between the NE0-D0 chip, pin 40 and NE0-B0 pin 41. The Z80 Error returned during testing and the IRQ pins on the CPU had bad signals. Pins 36 and 37 on the NE0-D0 read 50 ohms between them. This drove the NMI and IRQ lines for the Z80 CPU. Removed the NE0-D0 IC, cleaned the rodent damage under it, and reinstalled it and the patch to the B0 chip. Tested.

The rodent damage corroded the solder on the plated thru holes under the NE0-D0 IC. This corrosion was bridging the 2 pads causing the problems.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:21:29 PM
Model: MV4
Symptom: Constantly reboots with Calendar Error

System was odd in that it would come up with a Calendar Error message then reboot. The reboot was odd since the system should've stayed on the Calendar Error screen. Disassembled system only to find that it worked fine. Tapping the board caused the problem to intermittently return. Resoldered bad connections on the surface mount Work and Backup RAM to fix.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:21:40 PM
Model: MV4
Symptom: Locks up in Attract mode. Sounds stop working at times. Won't keep high scores.

Replaced bad battery to fix score issue. Board would reboot if carts bumped or jiggled. Cleaned the top board and slots then tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:21:49 PM
Model: MV4
Symptom: No sound

Reset backup RAM and then had low volume on right channel and no audio on left. Installed audio cap kit. Replaced leaking battery. Cleaned top board and slots then tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:22:03 PM
Model: MV4
Symptoms: Carts won't play and Z80 Error

Cart in slot 1 wouldn't play and in slot 2 gave a Z80 Error. Board was described as having "shipping damage" and the battery came off from the spot welded leads and bounced around between the boards.

DIP switch 8 was on. This is the 'pause' switch which caused the game to freeze upon booting and not play any carts. The Metal Slug cart shipped with the board was dirty. This was causing the Z80 Error. Playing with test carts showed the system had garbled sound effects. No traces were damaged. Swapped out the 74LS244 and 245 chips buffering the sound data. No change. Replaced the YM2610 sound chip to fix the sound issue and tested. Cleaned the Metal Slug cart and tested.

Per customer, replaced the battery and missing screws. Replaced 1 PC board standoff that had crossed threads.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:22:16 PM
Model: MV4
Symptom: Video RAM Error $8000, Written 5555 Read 0055

Replaced bad SRAM IC and tested. Board had low audio. Installed audio cap kit to fix audio issue. Cleaned top board & slots. Replaced 2 missing screws, 2 stripped screws, a broken standoff, and a broken mounting foot. Tested system.

The standoff and foot were broken due to insufficient packing in the box.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:22:25 PM
Model: MV6
Symptom: No audio

Could not put board on bench without first contacting customer. The NiCd battery on the board was replaced by a NON-rechargeable lithium battery and the charging circuit was NOT disabled. This was dangerous.

Replaced battery with a NiMH rechargeable type, installed Audio Cap Kit, and tested. Replaced one incorrect standoff and reassembled system then retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:22:35 PM
Model: MV-2
Symptom: vertical lines in game

Board had a leaking battery that caused trace damage. Jumpered 2 bad traces between the NE0-ZMC2 and the NE0-257 IC, replaced the bad battery, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:22:51 PM
Model: MV-2F
Symptom: Video RAM Error

Video RAM ERROR $8000, Written 5555, Read FFFF

Replaced both CXK-5814 SRAM chips. Tested board. Replaced leaking backup battery and tested again.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:22:58 PM
Model: MV4
Symptom: Garbled graphics and text

The top board had corrosion damage from either a liquid spill or rodent urine. Removed 2 74LS245 and 5 74LS244 chips from the top board. Cleaned the board and checked for trace damage. Installed new chips, repaired 3 traces, and tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:23:06 PM
Model: MV4
Symptom: Video RAM Error

Video RAM Error $00000005 Write 5555 Read 5557

Replaced bad SRAM IC at K9 and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:23:15 PM
Model: MV4
Symptom: Crosshatch of death

Board had a leaking battery but the traces were still OK. Removed the battery & cleaned the residue. Tested traces and found no bad ones. The 74LS138 on the upper board that selects the slots had no signal on pin 4. Replaced bad 74AS244 on the bottom board. All traces were good and all address lines to the carts were good but the system still would not read the carts. Replaced 2 74AS245 ICs interfacing the cartridge data lines on the bottom board and tested carts in all 4 slots.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:24:35 PM
Model: MV2F
Symptom: Corrupt Graphics

Board had a very strange symptom: Character graphics on the left side of the screen and the background graphics were flipped left-to-right on 8 bit boundaries. Text overlay and health bar resources were fine. When the LSPC2 and NEO-B1 chip were tapped, the system would reset. Resoldered pins on both chips to fix the reset issue but the graphics corruption remained. Checked the H signal from pin 109 of the LSPC2 to pin 7 of the NEO-ZMC2 and it was good. This signal is used for flipping graphics elements.

Replaced the NEO-ZMC2 IC and tested the board. Per customer's request, installed a coin cell battery mod: Removed the 470 ohm charging resistor then installed a CR2032 batter and holder. Reset Backup RAM and set the time/date. Re-tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:24:44 PM
Model: MV4
Symptom: Garbage on screen. Dead.

Board had battery damage.

Cleaned the corrosion from the bottom board and from the connector on the top board. Pinned out all the traces to find out where the damage was... They were all good. Found a broken trace on D4 between the Work RAM and the Backup RAM. Jumpered the trace, no effect. The solder joints and some of the legs were pretty badly damaged by the battery leakage on the Work RAM and the Backup RAM. Removed the RAM, cleaned up the pads, installed new RAM, reinstalled the jumper on D4, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:24:53 PM
Model: MV4F
Symptom: Z80 Error

Replaced Z80 IC and tested. Audio levels were low so a cap kit was installed. Board had audio during self tests but not while playing games. Cleared the Backup Memory from within the Hardware Test Menu and tested the system.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:25:01 PM
Model: MV1T
Symptom: Garbled audio

Cleaned Stereo/Mono switch and tested. Board had a leaking NiCd battery. Removed the battery, cleaned up the solder pads, removed the 470 ohm charging resistor and installed a CR2032 battery and socket. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:25:08 PM
Model: MV4
Symptom: Video RAM Error

Replaced 1 surface mount SRAM chip and installed an audio cap kit to fix low audio volume issues. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:25:15 PM
Model: MV1FS
Symptom: No video sync

Board was covered in an oily residue and had a leaking battery. Cleaned board then patched a bad trace between the LSPC2 and the NEO-IO chips. Removed the 470 ohm charging resistor and installed a lithium coin cell battery and holder. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:25:23 PM
Model: MV2F
Symptom: Video RAM Error $8000

Replaced 2 CXK-5814 SRAMs. Audio had issues. Replaced 2 470uf caps and removed a solder short from the audio amplifier section. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:25:34 PM
Model: MV1
Symptom: Video RAM Error $8000

Replaced 2 CXK-5814 SRAMs and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:25:45 PM
Model: Metal Slug 5 (all-in-1 game board)
Symptom: Graphic corruption

Resoldered 4 broken solder connections on Graphic ROM C4. Tested game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:25:53 PM
Model: Metal Slug 3 (bootleg cart)
Symptom: Dead

Resoldered SMT program ROMs and the controller IC for them. Cleaned edge connectors and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:26:01 PM
Model: Metal Slug 3 (bootleg cart)
Symptom: Dead

Removed shorting solder splashes from an empty program ROM chip location. Resoldered program ROM control chip, cleaned edge connectors, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:26:12 PM
Model: King of Fighters 2003 (bootleg)
Symptom: Dead

Resoldered the control IC for the Program ROMs. Fixed one short between the RAM on the cart and the ROM where the wire was to tight going around a sharp pin and the insulation was pierced. Cleaned edge connectors. Game played but with garbled sound effects. Resoldered the sound effects ROMs and their control chip. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:26:19 PM
Model: MV4F
Symptom: Z80 Error

Replaced bad Z80 IC. Removed leaking battery, cleaned board, and installed new battery. Cleaned top board and slots. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:26:27 PM
Model: Metal Slug 4 boot
Symptom: Dead

Cleaned cart edge connector and tested
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:26:35 PM
Model: Super Sidekicks 2
Symptom: Graphic corruption

Cleaned cart and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:26:42 PM
Model: 1 slot (bootleg)
Symptom: Graphic corruption

Board came in with a complaint of graphic corruption but was dead. The CPU was a PLCC type and was in a socket. Pulled the CPU, cleaned the severely tarnished legs, and reinstalled. System booted with the graphic corruption. Cleaned the legs on a 27C512 EPROM and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:26:59 PM
Model: MV4
Symptom: Low audio and graphic corruption

Recapped the audio section of the board and cleaned the top board and slots. Replaced the battery and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:27:07 PM
Model: MV4
Symptom: Stuck at crosshatch

Replaced connector CN10 on the upper and lower board. Battery corrosion caused it to not make proper connection. Cleaned the top board and slots then tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:27:13 PM
Model: MV4
Symptom: No audio and graphics corruption

Replace NEO-B0 chip to fix graphics corruption. Installed audio cap kit and new battery. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:27:20 PM
Model: MV4
Symptom: No audio. Missing parts

Board was purchased as "non-working, no audio" for refurbishing. Replaced missing LM324 op-amp and HA13001 audio amplifier IC. Patched 2 broken traces and installed audio cap kit. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:27:27 PM
Model: MV6
Symptom: No audio

Board was bought for refurbishing and resale. It had already been worked on. Replaced 2 incorrect and 1 backwards cap in the audio section. Still no sound. Checked the YM3016 DAC and it's inputs were dead. Replaced the YM2610 and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:27:36 PM
Model: MV4
Symptom: Corrupt graphics and lockups

Board has been previously worked and has damage from it. BIOS has been replaced with a UniBIOS chip.

Replaced the surface mount video SRAM previously installed by the other tech. Patched 2 damaged traces. Board booted to a backup RAM error. Replaced the bad backup RAM. Replaced the UniBIOS with a standard BIOS. Board booted to a Video RAM error. Replaced the other surface mount SRAM and tested. Board had very low audio. Recapped audio section and replaced the battery with a new one. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:27:43 PM
Model: MV4
Symptom: Stuck in watchdog

Board has been previously worked on and has damage from it. BIOS is missing.

Replaced missing BIOS and 1 missing video SRAM IC. Jumpered a damaged trace and tested system. System booted with a Z80 error. Removed SIP strips used as a Z80 socket from the board. Removed 2 terrible trace patches and tested each trace coming from the Z80. The traces were damaged when the previous tech used a large screwdriver to pry the Z80 from the board.

Installed a new socket, new Z80, and 2 Kynar wire jumpers. Board still booted to a Z80 Error. Replaced bad SM1 ROM and retested. Board had almost zero audio when turned up full volume. Recapped the audio section and installed a new battery. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:27:50 PM
Model: Metal Slug 4 cart
Symptom: Graphic corruption. Locks up.

Cleaned cartridge edge connector and tested. Cartridge edge connections were too dirty to clean with q-tips and alcohol and had to be cleaned with a pink pencil eraser.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:27:57 PM
Model: King of Fighters 2000 Cart
Symptom: No audio, severe graphic corruption

Graphics were nothing but scrambled colored dots on the screen and were not recognizable at all.

Jumpered cut trace where the cartridge was mounted. Reflowed surface mount IC NEO-CMC and tested.

Some Neo Geo cartridges have traces that run under the plastic board mounts in the cart shell. These traces can be cut or worn through by the plastic.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:29:15 PM
Model: King of Fighters 96
Symptom: Corrupt Graphics

Cleaned the cartridge edge connectors with a pink pencil eraser and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:29:23 PM
Model: MV1F
Symptom: Video RAM Error $8000

Replaced bad CXK5814 SRAM chip and tested. Board had a badly leaking battery. Removed the battery and a 470 ohm resistor from the charging circuit. Cleaned the board and installed a coin cell battery holder and CR2032 battery.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:29:30 PM
Model: MV1
Symptom: Backup RAM Error

Board had a leaking backup battery which ate traces. Removed the battery, replaced 1 SRAM chip, and jumpered 3 corroded traces. Board would boot but was stuck on a green screen - a calendar error. Jumpered a bad trace and replaced the 32.768KHz crystal for the clock/calendar chip and tested. Board would not read DIP Switch 8. Jumpered another bad trace, installed a coin cell battery and holder then tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:29:36 PM
Model: MV1
Symptom: Stuck on green (Calendar error)

Board had a leaking backup battery which corroded the 32.768KHz crystal for the clock/calendar chip. Removed the battery, replaced the crystal, installed a coin cell battery and holder then tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:29:42 PM
Model: MV4
Symptom: Dead. Nothing on screen.

Replaced bad Work RAM, cleaned top board, installed coin cell battery kit, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:29:50 PM
Model: MV2
Symptom: Stuck in watchdog

Board came in with garbage on screen and clicking sound, a classic stuck in watchdog problem. Replaced bad BIOS chip, replaced 2 bad SRAM ICs, removed leaking battery from board, cleaned, installed coin cell battery mod, then tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:29:57 PM
Model: MV2
Symptom: Stuck in watchdog

Removed leaking battery and cleaned board. Removed damaged memory card slot connector. Its pins were bent and touching each other. Board was then stuck in Calendar (green screen). Replaced crystal to no effect. Replaced D4990 IC and tested.  Removed the 470 ohm resistor then installed a coin cell battery and holder in place of the NiCd battery. Replaced physically broken headphone jack and headphone volume control. Installed a replacement memory card slot connector then tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:30:03 PM
Model: MV4
Symptom: Work RAM Error

Replaced a bad surface mount Work RAM IC and tested. Board then came up with a Video RAM Error message. Replaced another bad surface mount SRAM and tested. Board had poor audio levels. Installed an audio cap kit, replaced the leaking battery with a coin cell conversion kit, and tested.

Cleaned the top board, reset the calendar, and tested one last time.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:30:12 PM
Model: MV2F
Symptom: Cannot control audio on left channel

Left channel audio was full blast and couldn't be controlled by the volume slider. Recapped audio section, replaced volume control, replaced leaking battery with a NiMH battery, and cleaned the board. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:30:17 PM
Model: MV4
Symptom: Video RAM Error $8000

Replaced bad CXK-5814 SRAM IC. Board had no audio. Recapped audio section then tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:30:26 PM
Model: MV2F
Symptom: Backup RAM Error

Board had battery leak damage.

Cleaned the board. Patched 2 traces on the HC32 IC to fix backup RAM error. Patched 4 traces on the NE0-ZMC2 IC and one on one of the NE0-257 ICs to fix graphic corruption. Jumpered a bad power trace to fix the Calendar Error. Resoldered a popped pin on one of the NE0-G0 ICs to fix slot 2 not working.

Removed the 470 ohm resistor from the charging circuit and installed a coin cell battery and holder.

Retested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:30:33 PM
Model: MV2F
Symptom: Dead. Stuck in watchdog

Board had a leaking battery which damaged the board by eating several traces.

Replaced a bad BIOS IC and 2 Work RAM ICs then the board would boot but had graphic corruption and an intermittent Z80 error and no sound. Patched a bad trace on address line A7 between the SM1 ROM and the 6116 to fix the Z80 error and sound problem. Replaced a NE0-257 IC that had a pin corroded through. Patched a trace between the NE0-257 and the NE0-ZMC2 IC. Patched 4 traces between the 2nd NE0-257 and the NE0-ZMC2 IC. This brought most of the graphics back. The output of the NE0-ZMC2 IC was racing on one pin. Replaced the NE0-ZMC2 IC to finish fixing the graphics issue.

Removed the 470 ohm resistor from the charging circuit and replaced the leaking battery with a coin cell holder/battery.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:30:41 PM
Model: MV2
Symptom: Dead. Click of death.

Board had batter leak damage.

Replaced the Work RAM and Backup RAM. Fixed a bad trace in the battery backup circuit. Board booted with a Backup RAM error. Jumpered a corroded trace to the upper Backup RAM's R/W line. Removed the 470 ohm resistor and installed a coin cell battery and holder. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:30:48 PM
Model: MV4FT2
Symptom: Crosshatch of death

Board had no battery leak damage and had already been converted to a coin cell battery. Board would only recognize cartridges when tilted up on its side, otherwise it was stuck on the crosshatch.

Board had been previously worked on. Someone replaced the caps and put large blobs of solder on every joint. All of the surface mount ICs on the top board had been reflowed.

Used liquid rosin flux and a hot iron to properly flow all the solder on the caps. Jumpered one damaged solder pad. Connector CN10 on the top board had come apart and wasn't fully seating to the bottom board. If pressure was put on the connector the games would boot. Replaced the bad connector and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:30:54 PM
Model: MV4
Symptom: Video RAM Error

Replaced 2 CXK5814 SRAM chips and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:01 PM
Model: MV1F
Symptom: Z80 Error

Board had been worked on previously and had the Z80 replaced.

Board had damage under the Z80 socket. Removed the socket, traced out the connections, installed a new socket, jumpered 2 bad traces, and reinstalled the Z80. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:07 PM
Model: MV2F
Symptom: Garbage on screen

Board had a Video Memory error which was causing garbage on the screen. When the pins on the chip were touched it would change the screen image drastically. Board had some liquid damage on the Video RAM that ate the trace to address line A0. Jumpered one trace and tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:12 PM
Model: MV6
Symptom: Calendar Error

Could not duplicate issue. Resoldered customer installed clock/calendar crystal. Cleaned board set, installed audio cap kit, and a coin cell mod kit. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:19 PM
Model: MV4
Symptom: No audio

Board was worked on by another tech and was missing an IC

Replaced missing audio DAC. Tested. Board had no audio but did have digital audio working. Recapped board. Board worked but had audio corruption. Replaced bad YM2610 and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:29 PM
Model: MV4
Symptom: Low audio with scratchy sounds on all slots

Recapped audio section to fix low audio. Board not only had scratchy sounds but other sounds would mysteriously drop out. Replaced a bad YM2610 audio IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:38 PM
Model: MV4
Symptom: Stuck on Green (Calendar error)

Removed leaking battery. Replaced bad clock/calendar crystal, cleaned board, and tested. Repaired one bad trace on the data lines running under the battery. Installed coin cell battery mod. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:45 PM
Model: MV1
Symptom: Graphic corruption

Removed leaking battery and cleaned board. Repaired a bad trace on the cartridge riser board. Tested. Installed a new NiMH battery, reset NVRAM, and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:51 PM
Model: MV2
Symptom: Graphic Corruption - leaking battery damage

Battery was already removed from the board. Removed the corroded NEO-ZMC2 IC. Cleaned the pads and installed a replacement ZMC2. Ran 5 jumper wires to patch bad traces to/from the ZMC2. Ran a jumper from slot 2 to the NEO-257 IC buffering one of the Graphics ROM banks on the cartridge to fix the remaining graphics corrosion. Tested board. Installed a new NiMH battery, reset the backup RAM, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:31:58 PM
Model: MV1
Symptom: Garbled graphics

Board had been worked on before, but didn't appear damaged.

Removed component lead from under the peeled back cardboard/foam protector on the bottom of the board. It was shorting out traces under the foam. Reflowed the solder joints on a customer installed cap kit. Cleaned riser board/slots. Replaced the NiCD battery as it had just started getting crystalline growth on the negative side. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:32:06 PM
Model: MV4
Symptom: Backup RAM error: Read AA8A

Replaced bad SRAM at IC F9 and tested. Board had almost zero audio output. Installed audio cap kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:51:42 PM
Model: MV4
Symptom: Stuck on Crosshatch

Board had a leaking battery that was already removed before it was shipped in.

Cleaned bottom board. Cleaned top board and slots. Patched 3 bad traces that were damaged by the battery leaking. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:51:51 PM
Model: MV4
Symptom: Stuck on Crosshatch

Board had a leaking battery that was already removed before it was shipped in.

Cleaned bottom board. Cleaned top board and slots. Patched 3 bad traces that were damaged by the battery leaking. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:51:57 PM
Model: MV2F
Symptom: Audio issues

Installed an audio cap kit, remote battery, and replaced a broken headphone jack. Upgraded the system BIOS to a UniBIOS at customer's request using customer's supplied code. Repaired a broken trace to DIP Switch 8.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:52:06 PM
Model: Super Sidekicks 3 cartridge
Symptom: Graphic Corruption

Game had lines in the background graphics. Resoldered the Graphics ROMs to fix cracked solder joints. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:52:15 PM
Model: MV6
Symptom: Dead, stuck in watchdog

Board had burned resistors on the sync line from what appeared to be a faulty monitor connection. A previous repair attempt was made where the resistors had been replaced.

Removed a huge wire jumper from the board. Replaced a shorted 74AS244 IC, blown 74LS86 IC, and a shorted CPU. Installed a 30ga Kynar jumper to replace a burned trace. Cleaned the top board/slots. Replaced battery with a Coin Cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:52:23 PM
Model: MV4
Symptom: Dead. Will not power up.

Board had a diode installed between power and ground on the edge connector. This diode was shorted.

Removed shorted diode. Board would power up but had low volume issues. Recapped sound section. Board would play but had static in audio and was missing some sounds. Replaced bad YM2610 IC. Cleaned both boards and replaced battery. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:52:29 PM
Model: MV4F
Symptom: Random sounds and memory errors. Won't always recognize carts.

Removed leaking battery and cleaned top/bottom boards which fixed sound/cart issue, but the volume was low and would make popping sounds that affected the picture on the screen. Installed an audio cap kit and removed 2 bad mylar caps from the audio output circuit and tested.

Board would randomly crash upon warming up. Set all DIP switches to on to force a Work RAM test loop which tests Work RAM and Backup RAM. Board failed with a Backup RAM error after 10 minutes. Replaced bad Backup RAM and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:52:37 PM
Model: MV6
Symptom: Stuck on crosshatch

Cleaned top board and tested. Replaced battery at customer's request.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:52:43 PM
Model: MV1
Symptom: Z80 Error

Removed leaking battery and cleaned residue off of board. Cleaned slots and tested. Replaced battery.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:52:51 PM
Model: MV2F
Symptom: Backup RAM Error B240

Replaced bad 74HC32, 2 corroded transistors, 1 cap, and 1 open 22k ohm resistor in the battery backup circuit. Removed the 470 ohm resistor in the charge circuit and installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:52:58 PM
Model: MV-2F
Symptom: No audio from slot 2

Checked connections between the slots and the NEO chipsets. Continuity was good. Replaced bad NE0-257 IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:53:06 PM
Model: MV2F
Symptom: Horizontal graphical corruption.

Graphics had horizontal tears in graphics. Replaced NE0-E0 chip and the LO ROM. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:53:15 PM
Model: MV4
Symptom: No audio

Recapped the sound section and cleaned top board and slots. Reassembled boardset and replaced incorrect hardware, missing hardware, and 1 broken mounting foot. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:53:22 PM
Model: MV4
Symptom: Lines on screen and no sound

Cleaned top board and slots to fix graphic issue. Recapped bottom board to fix audio issue. Tested. Replaced one broken board standoff, 3 missing top cover screws, and a missing mounting foot.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:53:30 PM
Model: MV4
Symptom: Backup RAM Error 00D01C0A AAAA EAAA

Replaced bad surface mount SRAM IC and tested. Board had low audio. Recapped audio section and retested. Ran board on an extended Work RAM test to check those RAMs.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:53:36 PM
Model: MV1AX
Symptom: Backup RAM Error

Replaced bad RAM 3 and patched 2 corroded traces.

Board had the rechargeable lithium battery replaced with a standard coin cell, but did not have the charging circuit neutered. Removed D1, D2, and R10 to disable the circuit. Battery terminals still had 4.38v on it when the board was powered on. Replaced shorted diode D4 and tested. Reinstalled coin cell better and tested power to the Backup RAMs.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:53:43 PM
Model: MV4F
Symptom: Bad slot, low audio

Recapped audio section of the board. Replaced battery with a new NiCd per customer request, and replaced a physically damaged cartridge slot. Cleaned top board and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:53:53 PM
Model: MV4
Symptom: Dead. Garbage on screen.

Board had some attempted repairs done.

Reflowed the solder on 2 surface mount SRAMs that someone had attempted to replace. Resoldered the positive lead on the NiCd battery, recapped the audio, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:54:00 PM
Model: MV4
Symptom: Bad slot

Replaced bad slot connector, cleaned top board, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:54:08 PM
Model: MV4
Symptom: Bad slot

Slot 1 had garbage on the screen. Cleaned top board, replaced bad 74LS244 at location A4, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:54:14 PM
Model: MV1F
Symptom: Dead

Removed foreign substance from a Neo chipset chip and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:54:22 PM
Model: MV4
Symptom: Dead. Would randomly boot with graphic corruption

Resoldered the PRO-C0 and LSPC-A0 ICs to fix their cracked solder. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:54:31 PM
Model: MV1F
Symptom: Z80 Error

Board had severe battery damage. Cleaned battery damage, patched 5 traces on the sound system's SRAM chip, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:54:38 PM
Model: MV4
Symptom: Low Audio. Attempted Repair Damage

A ham fisted attempt had been made at replacing the audio caps. They had only replaced about 2/3rds and had damaged many solder pads and plated thru holes.

Removed all audio caps and other badly replaced caps. Installed new caps, patched traces, and soldered some caps in on the top side of the board where the plated thru holes were removed. Tested board and found that some sound effects were incorrect. Tested with a known good top board and narrowed problem to the bottom board. Replaced the YM2610 IC and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:54:47 PM
Model: MV4
Symptom: Video RAM Error 8000 5555 5500

Top board had a patched trace from a previous tech

Replaced bad CXK5814 SRAM chip. Audio levels were low so a cap kit was installed. Board had lines in the graphics on slot 4. Removed deteriorated foam that was corroding things from the under side of the op board, cleaned the glue/foam residue with solvent, cleaned board and slots, then checked the board traces. Re-ran the existing patch from a via to the chip instead of the slot to the chip as it was much shorter, then patched 2 additional traces. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:00 PM
Model: MV4
Symptom: Backup RAM error

Replaced both Backup RAM chips. Removed the foam from the underside of the bottom board as it was hardened and was causing corrosion of the board. Patched a corroded trace for the R/W signal to the Backup RAM. Board would boot but only slot 1 was working. Cleaned the top board, patched 8 bad traces, and tested. Board would play, but had incorrect sounds playing. Replaced a bad YM2610 IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:12 PM
Model: MV1F
Symptom: Low audio on right channel

Recapped audio section and tested. Installed a coin cell mod on the board and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:18 PM
Model: MV1
Symptom: Stuck on green screen

Cleaned board. Resoldered 32khz crystal and capacitors. Patched 2 traces to fix DIP switch 1 and 2. Recapped board to fix low audio issues on left channel. Replaced battery with a coin cell mod. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:26 PM
Model MV2F
Symptom: Calendar Error

Removed leaking battery, cleaned board, patched 6 corroded plated thru holes in the power circuit for the D4990 clock/calendar chip, replaced 1 diode, and installed a coin cell mod kit. Removed damaged memory card slot connector. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:32 PM
Model: MV2
Symptom: Video RAM Error 8000 5555 0000

Replaced 2 bad CXK5814 SRAM chip. Removed battery, cleaned the board, and installed a coin cell mod kit. Replaced damaged memory card slot connector with one from a parts board. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:39 PM
Model: MV2F
Symptom: Crosshatch of death. Severe trace damage.

Board was a parts board purchased in a lot. Someone had done a horrific job of removing the connectors from slot 2 and damaged many traces where they met the solder pads and in-between solder pads.

Removed battery and cleaned board. Removed the severely damaged memory card slot connector, installed 2 missing connectors for Slot 2 and tested. Board would not boot cartridges. Patched 1 trace for Address line A9 between the NEO-E0 at position F3 and Slot 1. Board would boot but not play sounds. Patched 2 traces between Slot 1 and Slot 2. Board would play carts in Slot 1 but in Slot 2 they had graphics and sound corruption. Patched 11 additional traces to restore Slot 2 to proper functionality. Installed a coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:45 PM
Model: Shock Troopers 2nd Squad (MVS Cart)
Symptom: Crosshatch

Replaced bad P1 ROM. Game played but had no sound. Replaced bad M1 ROM and tested game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:53 PM
Model: MV1
Symptom: Stuck on green

Cleaned corrosion from board as best as possible. Replaced a bad capacitor and crystal in the clock/calendar circuit. Tested traces around the area affected. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:55:58 PM
Model: MV1
Symptom: Stuck on green

Cleaned corrosion from board as best as possible. Replaced a bad capacitor and crystal in the clock/calendar circuit. Tested traces around the area affected. Tested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:56:04 PM
Model: MV4
Symptom: Low audio

Recapped audio section, cleaned top board, and replaced the battery with a NiMH type. Tested
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:56:14 PM
Model: MV4
Symptom: Lines on screen

Recapped bottom board, cleaned top board to fix lines, and replaced the battery with a coin cell kit. Replaced missing assembly hardware. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:56:20 PM
Model: MV4
Symptom: Will not play some cartridges

Fixed 1 burned trace and 2 gouged traces on the top board. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:56:27 PM
Model: MV4
Symptom: Work RAM error

Replaced bad SRAM IC. Tested board. Replaced sound caps and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:56:36 PM
Model: MV1FS
Symptom: System ROM Error, battery corrosion.

Removed old battery, cleaned board, and replaced the BIOS ROM. Tested. Repaired a bad trace between the sound RAM and the NEO-D0 chip to fix missing sound. Recapped the audio section to fix a low volume issue on the right speaker. Installed a coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:56:48 PM
Model: MV4
Symptom: Lines in graphics, random Z80 error, low audio.

Recapped audio section, cleaned the top board and slots, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:56:55 PM
Model: MV4
Symptom: Memory error, lines and blocks on the screen.

Customer requests the installation of a coin cell battery kit and UniBIOS.

Replaced 1 bad surface mount Work RAM and 2 bad surface mount Video RAM chips. Replaced the BIOS with a UniBIOS 3.1 (Registered Version), replaced the battery with a coin cell kit, cleaned top board, replaced a bad 74F253 on the top board, and tested. No sound. Replaced bad YM2610 and successfully retested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:57:10 PM
Model: MV4
Symptom: No audio

Board had (poorly) attempted repairs done. A 74AS244 was replaced, the audio caps were half done, and the HA13001 was standing off the board with the mounting hardware missing.

Recapped audio section. Replaced poorly installed HA13001 and installed missing hardware. Replaced bad YM2610 to restore audio during hardware tests. Board would play but had no audio. Another tech had replaced the 74AS244 at R1 and damaged a trace. Patched trace between pin 15 of the 74AS244 at R1 and pin 2 of the Z80 CPU at M1. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 09:58:47 PM
Model: MV1FS
Symptom: Z80 Error

Removed leaking NiCd battery and cleaned board. Jumpered 9 bad traces. Tested. Recapped audio section, removed the 470 ohm resistor from the charging circuit, and installed a CR2032 coin cell battery and holder. Retested board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2014, 10:00:50 PM
Model: Samurai Shodown IV cartridge
Symptom: No audio

Resoldered multiple cracked solder joints on the sound program and sound samples ROMs. Tested cartridge and had sound but poor graphics. Resoldered multiple cracked solder joints on the graphics ROMs and 2 74xx series chips. Tested cartridge and it was now stuck at a crosshatch screen. Resoldered multiple cracked solder joints on the program ROMs, cleaned the edge connectors with a pink pencil eraser, and successfully tested the cartridge.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on June 02, 2014, 10:21:47 PM
Model: MV2F
Symptom: Stuck on crosshatch

Removed leaking battery then cleaned the board and slots. Board would boot but had no sound and graphic corruption. When the logic probe was placed on one of the NEO-257 chips' pins for graphics on slot 2 lines would appear on screen for carts playing in slot 1. Replaced 1 bad NEO-257 chip. This fixed the lines on the screen but the screen still had corruption and no sound.

Address lines A0 to A5 were missing on the sound program ROM pins on both cartridge slots. Replaced the NEO-E0 in the sound subsystem and fixed both the sound and the remaining graphics issue. Recapped the sound section and installed a replacement NiMH rechargeable battery.

Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 06, 2014, 06:15:34 PM
Model: MV1FZ
Symptom: Dead. Labeled as "rained on"

Found no water damage, but did see severe power damage. Replaced 2 bad Work RAM, 2 bad Video RAM, 2 bad Sprite RAM, 2 bad Palette RAM, Sound RAM, and the SM1 ROM. Recapped audio section, cleaned upright board/slots, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 06, 2014, 10:11:28 PM
Model: MV2F
Symptom: Z80 Error

Replaced bad Z80. Board booted but had no sound and no signal from the YM2610 to the DAC. Replaced bad YM2610 and had sound only from the right channel. Recapped audio section, cleaned board, and replaced the NiCD with a coin cell mod kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 09, 2014, 01:04:27 PM
Model: MV4F
Symptom: "Blocks on screen"

Board powered up but would drag down the 5v line with the audio amp IC oscillating. Recapped the audio, replaced 2 bad mylar caps in the sound section, and replaced the 2 470uf power filter capacitors. Tested. Cleaned board and replaced the NiCD battery with a coin cell kit.

Note: The MV4F's audio IC will oscillate if power is dirty and if the 470uf power filter cap on the 12v line is defective.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 09, 2014, 01:07:30 PM
Model: MV2F
Symptom: Corrupt Graphics

Board symptoms would come and go if it was tapped for flexed. Resoldered cracked joints on the NEO-LSPC2 IC, recapped the audio section, and replaced the NiCD battery with a coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 14, 2014, 09:12:09 PM
Model: MV6
Symptom: Lines in graphics

Customer also wanted board recapped and UniBIOS installed.

Replaced bad PRO-CT0 IC to fix lines on screen. One of the inputs was shorted to ground. Recapped audio section, replaced audio power filter caps, installed UniBIOS 3.2 onto existing EPROM, and cleaned top board. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 06, 2014, 02:50:13 PM
Model: MV4 and 4 cartridges
Symptom: Work RAM Error. Audio is loud and distorted. Board had previous repairs done to it.

Replaced bad SRAM chip to fix the Work RAM Error. Replaced incorrect and axial capacitors installed on the bottom board. Narrowed sound problem down to the bottom board and replaced a bad YM2610 IC. Cleaned the top board. Cleaned the contacts on the four cartridges and resoldered cracked solder joints on several ICs on the Magical Drop II cartridge.

Removed a swollen non-rechargeable lithium battery, removed the 470 ohm resistor from the charging circuit to neuter it, and installed a coin cell holder with a CR2320 battery. Replaced 2 stripped headed screws, 1 cross threaded screw, and 2 missing mounting feet.

Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 17, 2014, 06:05:30 PM
Model: MV1FS
Symptom: Z80 Error

Patched multiple traces to the 6116 SRAM and tested. Replaced 4 caps in the audio section and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 15, 2014, 03:41:24 PM
Model: MV1FZ
Symptom: Will not coin up.

Replaced bad combo resistor/capacitor network buffering the coin input. Tested. Cleaned vertical slot board and recapped audio. Retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 22, 2014, 07:52:10 PM
Model: MV1
Symptom: RAM ERROR $8000

Replaced both CXK-5814 SRAMs and tested. Replaced leaking battery with a coin cell and holder. Removed 470 ohm resistor to neuter the charging circuit, set the clock/calendar, and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 22, 2014, 07:52:59 PM
Model: King of Fighters 2
Symptom: Corrupt Graphics

Resoldered several cracked solder joints on the graphics ROMs, cleaned the cart edge connectors, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 22, 2014, 07:53:53 PM
Model: Aero Fighters 2 and Metal Slug 4
Symptom: Garbled graphics

Cleaned edge connectors on both cartridges with a pink pencil eraser and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 23, 2014, 01:25:55 PM
Model: MV2F
Symptom: Graphic corruption

Cleaned board and slots. Replaced leaking battery with coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 23, 2014, 01:26:56 PM
Model: MV2F
Symptom: Liquid spill damage.

Cleaned board and slots. Replaced battery with a coin cell kit and tested. Board was missing some sounds. Replaced YM2610 chip and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 23, 2014, 01:28:56 PM
Model: MV1
Symptom: Graphics corruption and sound issues

Board would flash green on the screen and the sound would squeal. Replaced 3 bad power filter capacitors to fix green flashing and sound issue. The audio amp chip was oscillating because of poor power filtering and was causing the green flashing on the screen. Reflowed the LSPC IC to fix graphics corruption issue. Replaced the YM2610 to fix missing sound effects. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 23, 2014, 08:43:00 PM
Model: Art of Fighting cart
Symptom: Corrupt graphics

Resoldered cracked solder joints on the ROMs. Board improved but still had corruption. Reflowed the NEO-273 chip and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 23, 2014, 08:43:43 PM
Model: Baseball Stars 2
Symptom: Corrupt graphics

Resoldered cracked solder joints on the graphics ROMs. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 23, 2014, 08:44:05 PM
Model: League Bowling
Symptom: Corrupt Graphics

Cleaned cart edge connectors and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 06, 2014, 12:14:16 PM
Model: MV4F
Symptom: Calendar Error / Stuck on green

Replaced bad 32.768KHz crystal, cleaned top board, and tested. Recapped audio section to fix a low audio output issue. Retested
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 06, 2014, 12:18:38 PM
Model: MV4
Symptom: Garbage on screen after board was cleaned by cust.

Board had garbage on screen that matched a Video RAM error screen where the RAM is bad. Looked over the memory with a logic probe and noticed that bridging adjacent data pins did not result in a change on the screen. Checked the LSPC chip and found multiple lifted legs and missing factory solder on many legs. Straightened 2 bent pins and reflowed the side of the LSPC with the missing solder issues. Tested and found audio output was very low. Recapped the audio section and installed a coin cell battery kit at customer's request. Retested board.

I've seen a few Capcom 1943 and other boards of that era with missing solder on pins of SMT ICs, but this is a first for seeing this on an SNK board. :)
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 07, 2014, 10:58:03 PM
Model: MV4
Symptom: Will not read carts

Cleaned the top board and slots. Removed battery, cleaned under the battery, and patched one damaged trace. Disabled the charging circuit, pnstalled a coin cell battery, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 04, 2015, 05:48:42 PM
Model: MV4 with Blazing Star cartridge.
Symptom: No audio. Will not play carts.

Cleaned the top board and slots. Installed a coin cell battery mod and recapped the audio section of the board. Replaced 5 cross-threaded screws, 1 standoff, and 2 broken mounting feet. Tested.

Opened the cartridge, resoldered 6 cracked solder joints, and cleaned the edge connectors. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 08, 2015, 10:08:14 PM
Model: MV1FS
Symptom: Low audio, leaking battery.

Recapped the audio section, removed old battery, cleaned up leakage, and installed a coin cell mod kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 14, 2015, 11:43:37 PM
Model: MV2F
Symptom: Lines in graphics

Replaced bad NEO-257 chip and tested. Replaced battery with a coin cell kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 14, 2015, 11:44:54 PM
Model: MV2
Symptom: Dead

Board would boot once out of every 20 times. Flipped all DIPs and put it into Work RAM test loop and rebooted it repeatedly. Board came up with a Backup RAM error. Replaced bad RAM and tested. Replaced battery with a coin cell kit and retested
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 15, 2015, 12:13:24 PM
Model: MV2F
Symptom: Backup RAM error

Cleaned board and replaced corrosion damaged 22K ohm resistor in the backup RAM control circuit. Installed a coin cell kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 05, 2015, 08:47:34 PM
Model: MV4
Symptom: Backup RAM error. Problems reading carts.

Replaced bad backup RAM. Tested board and found slot 3 would not read carts. Replaced 1 connector, 2 74LS245, and 1 74F244 ICs for slot 3 and cleaned the top board/slots. Tested. Boardset worked but graphics were very glitchy on slot 3. Replaced the 2nd connector for slot 3 and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 29, 2015, 08:49:31 PM
Model: MV4
Symptom: No audio

Recapped the sound section to restore audio. Walked the board's owner through cleaning a cart using a fiberglass pencil then removed the NiCd battery from the MV4, neutered the battery charging circuit, and installed a CR2032 battery and holder on the bottom side of the board.

Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 17, 2015, 09:27:30 PM
Model: MV2F
Symptom: Will not read carts

Removed damaged memory card socket and tested. Removed battery and installed a coin cell modification to the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 17, 2015, 09:29:00 PM
Model: MV2F
Symptom: Backup RAM error

Board had battery leak damage.

Patched 2 traces to the 74HC32 next to the battery. Board would now boot but had scrambled graphics. Repaired 4 damaged traces connected to the NEO-ZMC2 chip and tested. Removed battery, cleaned around where the battery was, and installed a coin cell modification to the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 21, 2015, 09:45:05 PM
Model: MV1
Symptom: No sync

Repaired a burnt trace at the JAMMA edge connector to restore sync. Tested board and discovered it had no audio. Repaired a gouged trace on the bottom of the board in the digital sound section and tested.

Did the coin cell battery mod to the board and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 21, 2015, 09:46:30 PM
Model: MV4
Symptom: Video RAM Error

Replaced bad surface mount 62256 SRAM and tested. Discovered board had low audio. Recapped the audio section of the board, installed a coin cell battery mod, and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 23, 2015, 08:44:30 AM
Model: MV4
Symptom: No audio, battery low, not reading cartridges.

Recapped audio section, removed battery and installed a coin cell mod, and cleaned the top board to fix the cartridge read problem. Tested board. It was playing but missing some audio sounds and others were incorrect. Replaced bad YM2610 audio IC and tested.

Note: For Neo Geo boards, the batteries are NiCd rechargeables and must be run at least 24 hours in a month to keep the battery charged. Replacing the battery with a coin cell and neutering the charging circuit is better if this is for home use. It's also better in that it gets rid of the leak prone NiCd battery that causes horrible damage to the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 23, 2015, 08:45:23 AM
Model: MV4
Symptom: No sound

Recapped audio section. Boardset would play games but games were missing some sound effects and others were garbled. Replaced bad YM2610 IC and retested. Installed coin cell mod and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 02, 2015, 06:37:48 PM
Model: MV4F
Symptom: Corrupt graphics.

Board had low audio and the screen would shake when the volume was turned up.

Recapped audio section and replaced the 3 extra power filter caps to restore audio and fix the shake issue. Cleaned the top board and slots then repaired two gouged traces on the bottom board to fix the graphic corruption.

Installed coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 02, 2015, 06:42:28 PM
Model: MV4F
Symptom: Backup RAM Error

Written 5555 Read 0000

This was a problem with the control signals going to the Backup RAM. The battery was shorted internally so it was removed. The /OE and /CE lines were OK but the R/W signals were missing. Replaced the 74HC32. Traced the missing signal back from there through the HC32 to a 74HC259. The inputs appeared there on pins 1, 2, and 3 and 13 was high. Noticed that when the 4th input, pin 13 was touched by the logic probe tip the screen would turn white. Replaced the IC, same issue. Double checked and found that pin 13 was floating, but was tied high internally on the IC. Jumpered broken trace to pin 13 and tested the board.

Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 02, 2015, 06:45:55 PM
Model: MV4
Symptom: No audio on slots 1 and 2.

Cust states: No audio at all after installing cap kit.

Replaced 1 4.7uf cap that was twisted on top of the board. Resoldered 3 cap legs where solder was on the leg but it wasn't soldered to the pad on the board. The board had sound now during test mode but had screen shake when volume was turned up. Replaced 3 470uf power filter caps in the audio section and retested.

Removed the fishpaper and foam from the bottom side of the top board as it had started to corrode chip pins. Checked the area for trace damage and found none. Inspected the top side of the board and found a corrosion spot where something had damaged the board. Jumpered three damaged traces and tested.

Installed coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 09, 2015, 05:20:54 PM
Model: MV4
Symptom: Dead. Backup RAM Error

System was missing the /CS signal on pin 20. Jumpered a bad trace from the backup battery circuit to the 74HC32 controlling the enable lines to the SRAM. Error still there. Replaced the SRAM IC and tested. Board had graphical corruption. Tested with a known good top board and found the problem to be on the bottom board. Patched corroded trace to fix graphic corruption.

Top board was reconnected, the slots were intermittent, and I noticed an oily coating on the board from some kind of contact cleaner. Cleaned the top board and discovered slots 2 and 3 had graphical corruption. Patched two corroded traces and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 11, 2015, 08:59:15 PM
Model: MV6
Symptom: Won't read carts.

Board had attempted repair damage. Someone had replaced the 74AS245 data latches on the bottom board between the CPU and the Program ROM data lines coming from the top board.

Patched 4 damaged traces on the 74AS245 chips on the cartridge data buss. Cartridges would read on some slots and not others. Cleaned the top board and slots. Cartridges would now read but slot 5 had garbled graphics and the audio was low on the right channel. Patched damaged trace on the top board to fix slot 5 and turned the PCB standoffs under the cart slots to keep them from rubbing other nearby traces.

Installed audio cap kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 18, 2015, 06:41:06 PM
Model: MV4
Symptom: Z80 Error. Only 2 slots working.

Replaced the Z80 CPU and tested. No audio. Used a logic probe with audio to check the input of the Yamaha DAC and heard the digital audio present. Recapped the audio section to restore audio. Cleaned the top board and slots to fix the slot issues. Tested with cartridges to find the audio was scrambled up. Replaced the YM2610 sound chip and retested.

Replaced the NiCd battery with a coin cell conversion, reset the backup RAM, and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 13, 2015, 10:52:11 PM
Model: MV6
Symptom: No audio in left channel. Solder on the edge connector.

Board cover was damaged in shipping.

Recapped the audio section, desoldered lumped solder from the edge connector, and tested. Straightened bent metal cover and one bent standoff. Replaced 12 missing screws, 4 plastic washers, and 4 nuts. Retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 28, 2015, 12:52:09 AM
Model: MV2F
Symptom: Lines through text layer

Patched a corroded trace and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 28, 2015, 12:53:37 AM
Model: MV2
Symptom: Lines and garbage on the screen while game plays.

Problem would come and go when the board was tapped or flexed.

Resoldered 2 sides of the LSPC-A0 surface mount IC to fix multiple popped solder joints. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 28, 2015, 12:55:09 AM
Model: MV4
Symptom: No Audio

User installed a cap kit on the board.

Logic probe on pin 4 of the YM3016 DAC showed no digital audio was making it to the DAC from the YM2610 IC. Replaced the YM2610 IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 13, 2015, 10:34:57 PM
Model: MV1
Symptom: leaking battery

Replaced battery with a coin cell mod, recapped the board, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 13, 2015, 10:36:26 PM
Model: MV1
Symptom: Stuck on Green (Calendar Error), missing audio amp IC.

Replaced 32.768KHz crystal, 2 capacitors, the D4990 IC, and cleaned around those components to fix the Calendar error. Replaced leaking battery with a coin cell mod kit, installed missing audio amp IC, and recapped the board. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 13, 2015, 10:40:16 PM
Model: MV1
Symptom: Video RAM Error 00000001 Written 5555 Read 5554. Missing 3 ICs in the audio section.

Replaced bad lower surface mount Video RAM IC to only receive another Video RAM error, this time with the upper Video RAM IC. Replaced the upper surface mount Video RAM IC. Board booted to a Z80 Error. Patched corroded trace on the Clock signal to the Z80 and tested. Z80 error was still present. Replaced the Z80 CPU and retested.

Board booted but had no audio. Replaced missing YM3016 DAC, 2066 headphone amplifier IC, and HA13001 audio AMP IC. Tested board and had audio, but it was low. Recapped board to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 20, 2015, 10:38:02 PM
Model: MV1
Symptom: Dead

Board would randomly fail with Backup RAM errors at different locations, if it would even boot. Replaced 2 Backup RAMs, installed coin cell battery kit, and recapped the audio section. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 20, 2015, 10:40:35 PM
Model: MV1
Symptom: Dead.

Board would sometimes fail with click of death and other times with a solid white screen.

The enable signal was missing on the SFIX ROM. Patched 5 damaged traces on the bottom of the board and the board would boot to a green screen - A calendar error. Replaced a battery leak damaged 22pf capacitor and the 32.768KHz crystal in the clock/calendar circuit to fix that. Installed a coin cell kit, replaced the DIP switches, and recapped the audio section. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 20, 2015, 10:42:46 PM
Model: MV1
Symptom: Low audio. Leaking battery.

Cleaned battery damage and replaced it with a coin cell kit. Patched one damaged trace to the DIP switches. Recapped audio section to fix low audio and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 20, 2015, 10:45:31 PM
Model: MV1
Symptom: Leaking battery.

Cleaned battery damage and replaced it with a coin cell kit. Recapped audio section and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 01, 2016, 04:52:29 PM
Model: MV4
Symptom: No audio

Recapped audio section. Board had audio, but was playing test tones incorrectly. Replaced bad YM2610 and tested. Board would not boot cartridges. Cleaned top board and slots and retested. Replaced missing hardware and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 07, 2016, 10:56:27 PM
Model: MV2
Symptom: Vertical lines in graphics and Video RAM Error $8000

Replaced 2 CXK-5814 SRAM chips to fix the Video RAM error. Reflowed broken pins on the NEO-B0 and LSPC chips then replaced a defective NEO-ZMC2 chip to fix the graphics error. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 07, 2016, 10:58:46 PM
Model: MV4
Symptom: Video RAM ERROR $00000601

Replaced bad 62256 type surface mount SRAM IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 19, 2016, 11:30:27 AM
Model: MV4 & Metal Slug X cartridge
Symptom: Z80 Error

Replaced bad Z80 IC and tested only to find no audio outputs. Recapped board and tested but the board would not boot past the grid screen. Disassembled cartridge and cleaned the edge connectors witt a pink pencil eraser then successfully tested the game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 28, 2016, 06:29:58 PM
Model: MV2
Symptom: Lines in graphics.

Board had battery leak damage and had a coin cell mod done to it previously. Cartridge with game was reported to crash if slightly bumped.

Patched 6 damaged traces between the NEO-B0 and the NEO-ZMC2 IC and tested. Game was missing coin up sounds and other sounds in game. Replaced the YM2610 sound generator IC and retested. Cleaned cartridge edge contacts with a pink pencil eraser and resoldered the sound ROMs to fix cracked solder joint problems. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 07, 2016, 06:20:41 PM
Model: MV1F
Symptom: Z80 Error

Board suffered from battery leak damage. Patched 6 damaged traces with 30ga Kynar wire and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 15, 2016, 10:04:59 PM
Model: MV1FZ
Symptom: No audio

Board had attempted repairs and had been recapped.

The volume control would spin 360 degrees and was replaced. The audio amp would not "pop" the speaker on power up. Replaced the amp IC and now had background hiss but no audio. Replaced 5 caps and checked the plated thru holes around the Op Amp IC then replaced the Op Amp IC and tested.

The audio amp IC was dead and the Op Amp had signals going into it and nothing coming out.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 15, 2016, 10:05:49 PM
Model: MV4
Symptom: Backup RAM Error

Replaced bad 62256 SRAM IC and tested. Board had no audio. Recapped the audio section and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 18, 2016, 05:41:05 PM
Model: MV4
Symptom: Audio low

Recapped the audio section and tested. Replaced missing hardware under the slots and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 04, 2016, 11:49:10 AM
Model: MV2
Symptom: RAM error 00008200

Repaired corroded trace between LSPC-A0 pin 149 and pin 19 of the CXK-5814 RAMs. Board booted but had graphic corruption. Patched corroded trace on pin 151 of the LSPC-A0 and retested to find some lingering graphic corruption. Patched a broken trace between pin 51 of one of the NEO-E0 chips and pin 7 of the the 74LS244 near the LSPC-A0. Tested successfully.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 06, 2016, 07:37:39 PM
Model: Bermuda Triangle
Symptom: No audio

Replaced missing 8MHz crystal oscillator and a bad 1000uf @ 16v capacitor. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 07, 2016, 07:14:10 PM
Model: MV4
Symptom: Z80 Error

Replaced the Z80 Audio CPU and tested. Cleaned the top board, recapped the audio section, installed a coin cell battery kit, and replaced missing hardware. Retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 07, 2016, 07:17:17 PM
Model: MV4
Symptom: Dead

Replaced dead 74LS74 in the clock circuit and patched one burnt trace under it to restore the clock signal. Board was now showing garbage on the screen and was stuck with a click of death problem.

The chip control signals and address line signals were missing from the Backup RAM. Replaced the 68000 CPU and a bubbled up NEO-B0 chipset chip to get the game to boot. Replaced a 74LS245 and 74LS74 in the video output circuit and tested. Installed a coin cell battery kit and replaced missing hardware. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 16, 2016, 10:25:45 PM
Model: MV4
Symptom: Z80 Error

Replaced the Z80 CPU and the system booted to the crosshatch screen, but had no audio during the hardware tests. Recapped the audio section to fix the missing audio issue, but the board was missing several sound effects and the coin up sound was distorted. Replaced the YM2610 audio IC to restore all sounds. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 24, 2016, 07:54:45 PM
Model: MV4
Symptom: Crosshatch of death

Replaced the connector to the top board next to the battery, cleaned and patched 29 traces damaged by battery leakage on the connector. Replaced the matching connector on the top board and patched 2 traces damaged by battery leakage. Tested and found graphic corruption. Cleaned the top board, patched 2 traces on the bottom board, and tested to find no sound during game play. Patched another trace on the top board then retested successfully. Replaced the bad battery with a coin cell kit
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 24, 2016, 07:56:59 PM
Model: MV4
Symptom: Stuck on Green (Calendar Error)

Replaced the connector next to the battery that connected to the top board, cleaned around the area, and patched multiple dead traces. Cleaned the top board, replaced the matching connector to the bottom board, and patched 3 dead traces. Board still stuck on green. Patched a trace between the D4990 and the 74LS174 at H11 to fix the Calendar error and tested. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 24, 2016, 08:53:11 PM
Model: MV4
Tip: Troubleshooting Stuck on Green / Calendar Error

When troubleshooting the MV4 for Calendar Error messages or Stuck on Green, first inspect the power to the chip. Pin 14 should have battery voltage (minus a diode forward voltage drop) when the power is off and +5v when the power is on. If the voltage is missing, check the power trace coming from the battery backup area.

Next, check the crystal with an oscilloscope since most logic probes won't show any pulses for its low signal. If it is missing replace the crystal first. If that's not it then reflow the 2 small caps next to the crystal. If that's not it replace the caps. It's VERY rare for the D4990 to fail.

If you have crystal oscillation then check the connections to/from the D4990 for battery damaged traces and patch any dead ones with Kynar wire wrap wire.

Code: [Select]
Pin  Connection
1    +Battery
2    +Battery
3    +Battery
4    IC H11 Pin 7
5    (D4990 Pin 11) 22K ohm resistor in the charging circuit
6    (10K resistor SIP pin 6) IC H11 Pin 2
7    Ground
8    (10K resistor SIP pin IC H11 Pin 5
9    (10K resistor SIP pin 7) IC A6 Pin 17
10   (10K resistor SIP pin 5)
11   (D4990 pin 5) 22K ohm resistor in the charging circuit
12   XTAL
13   XTAL
14   +Battery
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 03, 2016, 09:40:04 PM
Model: MV4
Symptom: No audio from cartridge games

Board had attempted repair damage

Removed a partially cut off IC, fixed a short on a sound bus CPU line to that IC, and installed a replacement IC and socket and patched 2 burnt traces. Tested. CPU address line was still dead. Replaced the IC driving that CPU address line and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 08, 2017, 09:37:42 PM
Model: MV2
Symptom: No audio

Removed the leaking battery and cleaned the board. Audio tests worked but cartridges would not have any sound. Pin 24 (/OE) of the M1 ROM on the cartridge was stuck high. Backtracked it to find that one of the 2 pins on the cartridge edge connector for selecting the audio ROM was floating. Patched bad trace to restore audio. Removed the 470 ohm resistor from the charging circuit and installed a coin cell battery and holder. Set the clock/calendar and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 20, 2017, 07:06:54 AM
Model: MV2
Symptom: Dead

Replaced a missing 74LS157 IC on the board to find a Video RAM error at $8000. Replaced a bad Sprite RAM (2K x 8 DIP) to find graphics corruption and low audio on the left channel. Patched a bad trace on a NE0-257 IC and cleaned the board and slots to fix the graphics corruption then recapped the audio section to fix the output issue. Tested.

Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 03, 2017, 09:49:44 PM
Model: MV1C
Symptom: Garbled video

Replaced bad 62256 SRAM video RAM IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 26, 2017, 09:03:01 PM
Model: MV4
Symptom: No audio

Recapped audio section, cleaned the top board, and installed a coin cell battery kit. Replaced missing hardware and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 26, 2017, 09:04:43 PM
Model: MV4
Symptom: Graphic corruption

Cleaned the top board, repaired a gouged trace on the bottom of the bottom board, and tested. Board had low audio output. Recapped the audio section, installed a coin cell battery kit, and retested. Replaced missing hardware during reassembly.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 26, 2017, 09:05:21 PM
Model: MV4
Symptom: No audio

Cleaned the top board, recapped the audio section, installed a coin cell battery kit, and tested. Replaced missing hardware during reassembly.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 10, 2017, 08:05:31 PM
Model: MV4FS2
Symptom: Lines in graphics

Cleaned top board and replaced missing hardware. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 17, 2017, 06:39:03 PM
Model: MV4
Symptom: Garbled audio

Board was shipped with 2 carts

Cleaned the carts and they worked in every slot except for the Bust A Move which had garbled audio in slot 2. Cleaned the top board and replaced a slot connector. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 17, 2017, 06:40:06 PM
Model: MV4F
Symptom: Low audio and scrambled screen

If volume was turned up the screen would lose sync.

Recapped the audio section, including the power filter caps, and tested. Replaced the battery with a coin cell kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 17, 2017, 09:03:39 PM
Model: MV4
Symptom: No audio

Recapped audio section, cleaned top board, and installed a battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 22, 2017, 10:12:09 PM
Model: SNK vs. Capcom SVC Chaos all-in-one board
Symptom: Stuck on crosshatch

Found a solder smear shorting 3 pins of a surface mount custom IC. Reflowed the three pins and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2017, 06:51:00 PM
Model: MV4
Symptom: No audio

Recapped audio section of the board and cleaned top board. Installed coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 23, 2017, 06:51:58 PM
Model: MV2F
Symptom: Lines in graphics and battery leak damage

Patched dead trace between the NEO-256 and the NEO-ZMC2 chips. Installed coin cell battery kit and tested.

Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 08, 2017, 08:56:58 PM
Model: MV4
Symptom: Dead

Replaced missing BIOS chip and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 08, 2017, 08:57:44 PM
Model: MV4FT2
Symptom: Dead

Replaced missing BIOS chip and tested. Board still stuck in click of death (watchdog.) Data line D0 was stuck high. Replaced bad Backup RAM and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 08, 2017, 08:58:33 PM
Model: MV4
Symptom: Slots 1 and 4 dead

Slots worked with my test carts but the board had no audio. Recapped the audio section and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 01, 2017, 10:11:24 PM
Model: MV1FS
Symptom: Dead - Shuts down power supply

Fixed 2 bent pins on the upright board connectors and tested. Video would flicker and lose vertical hold when sounds played. Recapped sound section to fix an oscillating audio amp issue and tested. Removed the NiCd battery and 470 ohm resistor then installed a coin cell battery and holder. Retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 26, 2017, 07:05:09 PM
Model: MV4
Symptom: RAM ERROR 00000E81 5555 5155

Customer requested battery and cap replacement

Replaced bad RAM, recapped the audio section, neutered the charging circuit, and replaced the battery with a coin cell. Cleaned the top board and slots then tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 10, 2017, 10:49:29 PM
Model: MV1FZS
Symptom: Stuck in watchdog

Data line D0 was stuck high. Replaced 2 RAMs and a bad BIOS chip. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 03, 2017, 07:52:56 PM
Model: Neo Geo MV1F
Symptom: Only plays coin up sounds

Board would not play any audio other than coin up sounds, not even the self test sounds.

Battery leaked on the board. Removed the battery and the the corroded sound SRAM chip then cleaned the board. Tested and found no bad traces. Removed the 470 ohm resistor to neuter the charge circuit and installed a coin cell holder and battery. Installed a 24 pin socket and a replacement SRAM chip. Replaced a bad YM2610 sound chip and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 04, 2017, 08:21:14 PM
Model: MV1
Symptom: Dead

Board had battery damage. Checked traces, found one bad trace to the resistor pack next to the D4990, and patched it then replaced a battery damaged 20pf cap in the clock/calendar crystal circuit. Signals to the Backup RAM were present, but not cycling. Board made a couple of popping sounds out of the speakers and a quick check of the CPU clock showed it stuck low.

The 24MHz clock was missing and when probes were touched to the crystal the board would make more popping sounds out of the speakers. Replaced a bad 100 ohm resistor in the clock circuit and it was still dead. Replaced the crystal and the 2 20pf caps and it was still dead. Replaced the NEO-D0 chip and the board sprang to life with a Work RAM error on the lower chip. Replaced the chip and the board booted with a Backup RAM error on the lower chip. Replaced it and the board booted to the crosshatch. Self tests showed DIP 1, 2, and 8 were not working. Patched the damaged traces and retested. DIP 8 was still showing open but pushing on the top of the switch would make it connect. Replaced the DIP switch, removed the 470 ohm resistor, and installed a coin cell holder and battery. Played a few games of Metal Slug to test it.

Upgraded the BIOS to the latest free UniBIOS chip at the customer's request.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 08, 2018, 10:16:48 PM
Model: MV4
Symptom: Backup RAM Error

A local friend brought this one over. The board was stuck on the crosshatch of death. It had a leaky battery that ate traces under it going to the top board connector. He had jumpered all the traces there and afterwards the board was then either stuck in watchdog, constantly rebooting, or stuck with a Backup RAM error.

The Backup RAM had a missing control signal on pin 20. Jumpered a corroded trace in the battery backup section and tested successfully.

When the Backup RAM has no signals going to the control pins (20 and 22) it can spuriously output data onto the bus and crash the CPU. When you get odd things happening and when there are leaking batteries on Neo Geo boards always check the Backup RAM control pins, including the R/W on pin 27.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 05, 2018, 08:29:12 PM
Model: MV4
Symptom: No audio

The clock was missing to the DAC and no digital audio was making it to the DAC from the YM2610. Replaced bad YM2610 and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 05, 2018, 08:31:18 PM
Model: MV1F
Symptom: No sync

Board had corrosion damage on the NEO-IO chip from rodent droppings. Removed the chip, cleaned the board, cleaned the solder pads, reflowed the solder pads, cleaned the board, and cleaned the solder pads. Installed a replacement IC from a donor board, jumpered 2 corroded traces, and jumpered 2 missing pads. Tested. Audio fluttered. Recapped the audio, retested, removed leaking battery, and installed a coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 05, 2018, 10:20:59 PM
Model: MV1
Symptom: RAM ERROR: 8000 5555 555F

Replaced bad CXK-5814 SRAM chip. Board came up with an error 5755 afterwards. Replaced the other CXK-5814 SRAM chip and tested. Recapped the audio section and installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 15, 2018, 08:41:09 PM
Model: MV4
Symptom: Lines in graphics on slot 3, low audio, change battery

The fishpaper/foam protector on the bottom side of the board had its foam go bad. When this happens it corrodes traces. Repaired a bad trace going to one of the 74LS253 data selector inputs to fix the lines on slot 3. Recapped the audio section to fix the low audio issue. Removed the leaking battery and the 470 ohm resistor. Cleaned the area under the battery, installed a coin cell holder and CR2032 battery, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 03, 2018, 06:09:08 PM
Model: MV2F
Symptom: Backup RAM Error

Replaced the 74HC32 and patched a trace under it to fix the Backup RAM error. Repaired broken trace between the NEO-ZMC2 and the NEO-257 at 2/3J. Slot 2 now would play normally, but Slot 1 had lines in the display. Replaced bad NEO-257 at 2/3J and retested. Installed coin cell kit and retested again.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 03, 2018, 06:10:11 PM
Model: MV4
Symptom: Backup RAM Error

Repaired broken trace between the 74HC32 and the Backup RAM. Installed 6 missing feet and standoffs. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 03, 2018, 06:10:40 PM
Model: MV4
Symptom: No Audio

Cleaned top board. Recapped audio section then installed a coin cell kit. Tested. No Audio. Repaired bad trace between Z80 and Sound RAM then retested successfully.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 03, 2018, 06:12:20 PM
Model: MV4
Symptom: Crosshatch of death

Patched trace to fix crosshatch issue. Clock was counting hyper fast. Replaced bad D4990 Clock/Calendar chip. Cleaned top board, installed 6 feet and standoffs, installed coin cell kit, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 03, 2018, 06:13:21 PM
Model: MV4
Symptom: No audio

Cleaned top board. Recapped audio section, installed coin cell kit, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 03, 2018, 06:14:46 PM
Model: MV4
Symptom: Dead

Cleaned top board, installed missing BIOS chip, and tested - Video RAM errors and color errors. Replaced the sprite RAM, 1 74LS273, and 1 74LS05 to fix the video issues and tested - no audio. Replaced bad YM2610 and recapped audio section. Installed coin cell kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 09, 2018, 08:44:07 PM
Model: MV2
Symptom: Lines on screen. Board had battery damage.

Replaced a bad NEO-ZMC2 IC and patched one trace. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 21, 2018, 11:55:49 PM
Model: MV4
Symptom: Work RAM Error

Replaced both Work RAMs. Board came up with a Video RAM error at 000000. Replaced bad Video RAM and tested. Board was stuck on green - a calendar error. Removed leaking NiCd battery and patched 2 traces for the Clock/Calendar circuit that traversed the battery area. Tested board and it was stuck on the crosshatch of death. Patched one dead trace under the old NiCd battery and successfully tested the game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 21, 2018, 11:58:13 PM
Model: MV4F
Symptom: Dead. Displays an orange screen.

Replaced corroded BIOS socket and cleaned the legs on the ROM. Noticed that when the NEO-B1 chip was touched the screen went crazy. Reflowed 1 1/2 sides of the NEO-B1 and NEO-LSPCA2 chips and tested. The left audio channel was missing. Installed a cap kit and retested successfully.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 21, 2018, 04:00:09 PM
Model: MV4
Symptom: Low volume out of one channel. The other is dead.

Recapped the audio section and tested. Music was present but game effects were not.. Replaced the YM2610 sound chip to fix the missing sound effects. Replaced battery with coin cell kit, cleaned the top board, and reassembled/tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 21, 2018, 07:05:55 PM
Model: MV2F
Symptom: Lines in graphics

Checked inputs and outputs to the NEO-257 ICs and inputs to the NEO-ZMC2. All appear OK. Checked output traces from the NEO-ZMC2 and they were good. Replaced bad NEO-ZMC2 and tested. Removed the leaking NiCd battery and replaced it with a coin cell kit after neutering the charging circuit.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 22, 2018, 12:48:54 AM
Model: MV1
Symptom: Stuck on green

Removed the leaking battery, 2 corrosion damaged capacitors, and the bad clock crystal from the board. Cleaned and installed replacement caps/crystal. Patched trace to fix DIP switch 1. Recapped audio to fix low left channel issue and installed a coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 25, 2018, 11:40:29 PM
Model: MV4
Symptom: Stuck on crosshatch.

Board had physical damage - burned ground contacts on the JAMMA connector and bodge wires soldered in to bypass them.

Removed bodge wires and repaired edge connector with copper trace tape. Removed battery connection pins and 470 ohm resistor. Tested the traces under the battery and found one bad. Patched the trace and tested. The board played but was missing sound and had lines in the graphics. Cleaned the top board and slots then retested without any issues. Installed the coin cell holder and battery and re-tested game.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 27, 2018, 12:09:23 AM
Model: MV4F
Symptom: Reboots when playing carts in slot 3 if you have credits on the right side coin mech

Turns out it reboots even without using the right side coin mech - it's dependent on cartridges. Metal Slug works fine but Shock Troopers and Samurai Shodown 3 cause a reboot and Shock Troopers 2nd Squad causes it to go into a click of death until power cycled.

Narrowed problem down to the top board and found a floating pin 6 on the NEO253 at E5. When the logic probe (with finger touching it) is touched to pin 6 the cartridge boots without issues. Pulled the program cartridge board slot from the top board to find the break in the trace and its destination. Patched trace between pin 6 of the NEO253 at E5 and cartridge connection B27 (PWAIT1 signal) to fix the boardset. Tested by playing Shock Troopers 2nd Squad through to the end.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 27, 2018, 08:59:23 PM
Model: MV4F
Request: Change battery, change broken connector, and check out.

Removed NiCd battery & 470 ohm resistor then installed a CR2032 holder and battery. Replaced broken 60 pin ribbon cable connector. Cleaned top board/slots and tested. Audio was low on left channel so an audio cap kit was installed. Replaced PCB feet and stripped screws and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 31, 2019, 01:17:18 AM
Model: MV1
Symptom: Z80 Error

Replaced bad Z80 CPU and tested. Patched dead trace on DIP 1 and installed audio cap kit to fix low audio. Installed coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 31, 2019, 01:18:59 AM
Model: MV4
Symptom: Crosshatch of death

Cleaned battery damage and patched 3 dead traces. Tested but board stopped working during testing. Replaced upper and lower 64 pin connector next to battery as corrosion had migrated up inside the connectors. Retested. In stalled coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 31, 2019, 01:21:39 AM
Model: MV4
Symptom: VRAM ERROR

Replaced bad surface mount 62256 chip to fix the video error and tested. Game played but had low audio. Installed audio cap kit and coin cell battery kit. Tested all four slots - slot 3 was dead. Cleaned the top board and slot 3 would play but had graphical errors. Replaced a bad slot connector and retested.

This one was a bit frustrating. Two pins of the slot connector broke between the connector and the PCB making intermittent connection: A16 and B18, causing the graphic corruption.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 29, 2019, 09:48:01 PM
Model: MV2
Symptom: Graphics corruption

The battery had leaked and damaged the board. Cleaned the battery damage, patched one open trace, installed a coin cell battery kit, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 22, 2019, 09:07:52 PM
Model: MV2B
Symptom: Z80 ERROR

Replaced bad Z80 CPU and tested successfully.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 09, 2019, 09:17:41 PM
Model: MV1FT
Symptom: "Swap battery and check board"

Board had no audio output. Speakers would pop slightly like normal when power was applied or removed. Logic probe on the YM3016 DAC showed no audio data was arriving from the YM2610. Hardware tests produced no audio. Removed leaking NiCd battery and neutered the charging circuit. Cleaned up battery leakage and patched 2 data traces going from the Neo chipset, across the battery, to the audio section to fix the missing audio. Installed a CR2032 coin cell holder and tested board successfully.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 12, 2020, 03:21:47 PM
Model: MV2
Symptom: Z80 Error

Found and patched a bad trace to fix the Z80 Error during hardware tests without a cartridge installed. Fixed and patched a trace between the Z80 and the NEO-G1 and tested. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on May 31, 2020, 10:59:51 PM
Model: MV4
Symptom: Low audio

Screen was blue tinted. Cleaned the edge connector and retested. Replaced the audio capacitors to fix the sound issue and installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on June 21, 2020, 07:17:36 PM
Model: MV2FS
Symptom: Video RAM Error $8000 Written 5555 Read 0055

Replaced bad CXK-5814 SRAM and tested. Removed leaking NiCd battery and 470 ohm resistor and installed a coin cell holder and battery. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 10, 2020, 09:59:10 PM
Model: MV2
Symptom: Vertical lines on screen

Tracked down an open trace on the NEO-ZMC2 and patched it. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 12, 2020, 01:44:18 PM
Model: MV4
Symptom: Stuck in watchdog

Replaced 2 shorted 74AS245 ICs between the CPU and the connector to the top board. Board booted but with lines on the screen. Cleaned top board and slots and retested. Board had no audio. Recapped the audio section and retested. Removed the battery and installed a coin cell kit. Reassembled the boardset and replaced missing hardware. Retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 12, 2020, 06:38:57 PM
Model: MV4
Symptom: Video RAM Error

Replaced bad video RAM chip and tested. Recapped audio to fix low volume issues, replaced the 2 caps on the top PCB, and replaced the battery with a coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 13, 2020, 10:44:22 PM
Model: MV1F
Symptom: Stuck in watchdog

Replaced bad BIOS ROM. Recapped audio to fix missing sounds. Removed battery, neutered the charging circuit, and installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 13, 2020, 10:45:04 PM
Model: MV1F
Symptom: Poor audio quality.

Replaced bad YM2610 sound chip to fix poor quality sounds. Removed battery, neutered the charging circuit, and installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 14, 2020, 02:49:09 PM
Model: MV4
Symptom: Z80 error

Board arrived with the description "YM2610 was replaced and now get Z80 Error"

Board had bad heat damage from the YM2610 replacement by a previous tech.

Found a short between 2 data lines on the Z80. Traced that back to a poor solder pot job on the YM2610 replacement chip sent with the PCB. Removed that, but still received a Z80 Error. Removed the YM2610 and 64 pin socket from the PCB. Cleaned the flux and other residues then inspected every trace to/from the YM2610. Surprisingly, all traces, solder pads, and plated-thru holes were intact. Removed stuck leg from Pin 32 hole on the PCB. Installed a replacement socket and reinstalled the YM2610 just to see another Z80 Error message. Replaced the YM2610 and board booted fine. Tested.

The YM2610 was lasered on top and solder potted - hallmarks of being counterfeit.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 20, 2020, 06:36:47 PM
Model: MV2F
Symptom: Resetting, sound and video corruption

Removed leaking battery. Cleaned PCB/slots, installed a replacement NEO-257 IC to fix the video corruption, installed a coin cell battery kit, and replaced the damaged memory card socket. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 20, 2020, 06:38:18 PM
Model: MV2F
Symptom: Won't boot (Stuck in watchdog)

Removed the battery and cleaned the area around it. Replaced bad BIOS IC, patched a trace on the 74HC32 in the battery backup area and tested. Patched a trace on the NEO-ZMC2 chip to fix graphics corruption and tested again. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 20, 2020, 06:41:41 PM
Model: MV2F
Symptom: Resetting (stuck in watchdog)

Removed the battery and cleaned extensive battery damage. Cleaned the PCB and slots. Replaced the 74HC32 IC and jumpered 2 bad traces. Replaced the bad BIOS chip and jumpered one bad trace on it. Board booted to an error in $8000. Replaced one bad Sprite RAM (CXK-5814 DIP RAM) and tested. Board played but was missing all graphics detail. Replaced bad NEO-ZMC2 chip and graphics returned, but was horribly garbled. Patched 6 traces and tested to find graphics were better, but still corrupt. Replaced bad NEO-257 IC with 4 stuck outputs and patched one bad trace between it and the NEO-ZMC2. Tested and the right audio channel was cutting in and out. Recapped the audio section, installed a coin cell battery kit, and retested successfully.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 20, 2020, 06:45:20 PM
Model: MV4
Symptom: Video RAM Error: $00000A0B

Replaced bad 62256 SRAM IC and tested to find a RAM error at $8000. Replaced both CXK-5814 Sprite RAMs to find a Z80 error. Patched 2 corroded traces off the A11 line of the Z80 CPU to fix the error, but the board had no sound. Replaced the YM2610 and tested. Audio was there, but was about 1/4 of normal volume. Recapped the audio section, installed a coin cell battery kit, and successfully tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 20, 2020, 06:47:10 PM
Model: MV6
Symptom: Video RAM Error $8000

Replaced 2 bad CXK-5814 Sprite RAM chips and tested. Board would not recognize cartridges. Replaced 2 bad 74AS245 chips on the bottom PCB and tested. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 03, 2021, 01:34:01 AM
Model: MV4
Symptom: Backup RAM Error

Replaced bad Backup RAM and tested. Board would not read cartridges. Removed battery, cleaned under it, and patched 2 damaged traces to allow system to see the cartridges. Cleaned the top PCB and installed a coin cell kit. Recapped the PCB to fix low audio issues and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 03, 2021, 01:35:42 AM
Model: MV1
Symptom: Graphics corruption

Board had attempted repairs - surface mount RAM done: 2 backup and 1 video RAM.

Check previous work then looked over the PCB. Found a solder blob wedged in the solder pins of the slot connector riser. Removed blob to fix video issue. Installed a coin cell kit and recapped the PCB to fix low audio issues. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 03, 2021, 01:36:26 AM
Model: MV4
Symptom: Work RAM error

Replaced bad work RAM. Installed a coin cell kit and recapped the audio section to fix low audio issues. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 08, 2021, 11:03:59 PM
Model: MV1
Symptom: Garbled Screen

Cleaned riser/slot PCB and installed coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 08, 2021, 11:04:50 PM
Model: MV1
Symptom: Won't boot

Board had a Backup RAM error. Replaced 1 SMT RAM chip and installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 08, 2021, 11:10:30 PM
Model: MV4
Symptom: Won't Boot

Board was stuck on click of death. Replaced 2x Work RAM, 2x Backup RAM, 2x 74LS245 to see the Data Bus improve at each step, but the board was still stuck on click of death. Pulled 2x 74HCT245 latching data from the 60 pin connectors for the optional and the board booted. Replaced them and to board was back to Click of Death. Found pin 19 stuck, causing the ICs to constantly output data to the bus, crashing the CPU. Traced it back and replaced the 74HC04 with a shorted input and the PRO-C0 chip with a shorted line to it. Installed a coin cell kit and a missing 1000uf cap on the top board and tested. Board would reboot if tapped or jostled in the slightest. Found battery corrosion in the board interconnect next to the battery. Replaced both the male and female connectors and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 08, 2021, 11:18:06 PM
Model: MV4
Symptom: Won't boot

Top board was so dirty it wouldn't read carts.

Cleaned top board, installed coin battery kit, and tested. Slot one had lines in the graphics. Patched a damaged trace and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 25, 2021, 02:22:17 AM
Model: MV4
Symptom: Won't see cartridges

Board had attempted repairs done.

Removed a solder short under the peeled back foam where someone had attempted to replace the 74F138 3-to-8 decoder used to select slots. Removed multiple unnecessary bodge wires. Tested. Removed the rest of the fishpaper and foam from under the top PCB as the foam had hardened and started corroding chip legs. Retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 29, 2021, 04:30:57 PM
Model: MV4
Symptom: No audio. Graphics error slot 3. Also cart errors on slot 3.

Cleaned both PCBs. Removed hardened foam and fishpaper from the top board. Cleaned residue and patched one corrosion damaged trace to fix the graphics issue. Patched another damaged trace to fix the cart issue. Installed new audio caps to fix no audio issue. Installed a YM2610 to fix a garbled sound problem. Installed a coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 29, 2021, 04:31:47 PM
Model: MV2
Symptom: Will not boot games. Black screen.

Found DIP 8 (Freeze) set to on and set it to off. Tested game. Installed coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 29, 2021, 04:32:29 PM
Model: MV4
Symptom: No sound on any slot. One slot dead.

Cleaned top PCB and slots. Installed battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 04, 2021, 07:33:07 PM
Model: MV4
Symptom: Backup RAM Error 7FFF

Replaced bad Backup RAM IC and installed battery kit. Installed some missing hardware and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 04, 2021, 11:57:45 PM
Model: MV4FT
Symptom: Garbled audio

Replaced YM2610 audio chip and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 04, 2021, 11:59:40 PM
Model: MV4
Symptom: Work RAM Error

Replaced lower Work RAM and tested. Board popped up a Backup RAM Error on the lower chip then died. Found R/W pin (27) floating. Removed hardened foam under the fishpaper insulator and found a corroded trace. Patched the trace and tested - no audio. Installed new audio caps and a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 10, 2021, 02:46:41 PM
Model: MV4
Symptom: Won't boot cartridges and lost sound prior.

Could not duplicate cartridge issues. All my test cartridges worked fine.

Recapped audio section and power filter caps on bottom PCB. Replaced cracked HA13001 audio amplifier. Board now had sound but some effects were incorrect. Replaced YM2610 sound chip and retested. Installed coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 11, 2021, 08:46:05 PM
Model: MV1FS
Symptom: Dead. Battery damage. Blue screen.

Odd description, but yes, had a light blue screen and a lot of battery damage. I decided to try and fix it as the damage hadn't gone to the bottom side of the PCB. Removed the sound RAM and cleaned the PCB. Tested traces. Installed a socket and a replacement SRAM chip. Ran 18 patch wires on the bottom of the PCB, 4 on the top side, and 1 from the top through to the bottom side. Tested. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 14, 2021, 09:41:00 AM
Model: Time Soldiers
Symptom: No sound

Replaced missing Z80B CPU and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 19, 2021, 12:54:16 PM
Model: MV4
Symptom: Crosshatch of death

Patched 4 traces. Cleaned battery area, neutered the charge circuit, and installed a coin cell battery and holder. Installed new audio caps. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on July 23, 2021, 10:02:31 PM
Model: Gold Medalist
Symptom: Graphic corruption and no sound

PCB had solder globs on the edge connector.

Cleaned the edge connector and patched a damaged trace. Reconnected a severed wire to the Graphics ROM daughterboard. No change. Found ROM 5 had a corroded socket. Replaced the socket and cleaned the pins on the ROM to fix the graphics issue. Fabricated a replacement heatsink and replaced the missing audio amplifier IC. Replaced 4 caps in the audio and power filtering circuits by the edge connector. Tested. No sound. The sound ROM daughterboard was inserted into the socket on the board incorrectly. Reseated the board and most sounds returned. The D/A audio consisting of a 74HCT374 and resistor ladder DAC sounds were missing. Separated 2 shorting pins between the 2 LM324 Op Amp ICs to fix the sound issue. Tested all inputs.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 06, 2021, 02:54:20 PM
Model: MV4FS
Symptom: No sound from left channel. Graphics corruption and problem reading carts.

Cleaned the connector pins that connect the bottom board to the top. Removed a solder short from 2 pins under the connector on Slot 2 on the top board. Recapped the audio section and removed a solder jumper off 2 pins of an Op Amp in the audio preamp. Removed 2 jumper wires connecting button 4 to Select. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 12, 2021, 06:10:51 PM
Model: MV1
Symptom: Backup RAM Error

Backup RAM Error was showing on the screen three times.

Reflowed shorted pins on a custom to fix the triple lines of text. Replaced bad RAM chip, HC32 chip with a shorted output, and patched a dead trace to fix the Backup RAM Error message. Installed coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 12, 2021, 07:47:32 PM
Model: MV2
Symptom: Corrupt graphics

Installed missing BIOS chip and tested to find graphic corruption on slot 2 that went away when the cart was wiggled. Cleaned the PCB and slots. Retested. Slot 2 worked fine but slot 1 showed graphic corruption that changed when the graphic ROM data lines were touched for the ROMs on slot 2. Checked pin 17 of the NEO-257 chips responsible for slot select and found it floating. Patched bad trace between the 2 NEO-257 chips for graphics slot selection and the NEO-257 used for sound ROM slot selection. Tested. Installed coin cell kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 30, 2021, 09:17:00 PM
Model: MV2
Symptom: Graphic corruption, battery damage

Board powered up with a Backup RAM error. Patched two corroded traces to fix that issue. Patched 4 additional corroded traces to find a screen where every 8 bits of data was reversed. Replaced bad NEO-ZMC2 chip and tested. Every other vertical line was missing on the screen. Patched another trace to the ZMC2 chip and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 30, 2021, 09:18:18 PM
Model: MV2
Symptom: Graphic corruption, battery damage.

Patched 4 traces to the NEO-ZMC2 chip. Slot 2 had graphic corruption. Traced that to a bad output on a NEO-257 chip. Replaced the NEO-257 and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 30, 2021, 09:18:43 PM
Model: MV2
Symptom: Backup RAM Error

Replaced both backup RAM chips and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 30, 2021, 09:20:26 PM
Model: MV4
Symptom: Low, garbled sound

Board had a cap kit installed by another person

Removed a short between 2 capacitors where the legs where cut at the same time, crimping them together. Removed 3 220uf and 5 100uf caps that were physically too big and replaced them with proper caps. Cleaned the slots and top board. Replaced missing hardware and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 03, 2021, 08:58:24 PM
Model: MV4
Symptom: Parts board. Dead.

Replaced missing 74LS368 and missing volume control and tested. Solid colored screen that changed colors on power cycling. Replaced dead lower Video RAM, upper Work RAM, lower Palette RAM, and both sprite RAMs. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 03, 2021, 08:59:09 PM
Model: MV2
Symptom: Corrupt graphics

Cleaned around the battery area. Patched dead traces going from the NEO-257 to pins 10 and 11 of the NEO-ZMC2. Installed a coin cell kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 03, 2021, 09:00:35 PM
Model: MV2F
Symptom: Backup RAM error

Board booted fine, put it in Work RAM Test mode and it promptly failed with a Backup RAM error: B255 then after power cycle: B240. Cleaned around the battery area and replaced a bad 22K resistor in the Backup RAM control circuit. Tested. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 03, 2021, 10:47:08 PM
Model: MV2F
Symptom: No audio

Board had audio in test mode. Checked traces and found no damage. Reset Backup RAM to restore sound. Installed coin cell battery kit, reset Backup RAM again, set clock, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 07, 2021, 08:44:25 PM
Model: MV4
Symptom: Blocks on screen

Cleaned bottom and top PCBs. Patched damaged trace on bottom board to fix calendar error. Patched 4 traces on bottom board to fix address and data line connections to the top board interconnect for accessing the Program ROMs. Tested. Patched damaged trace on the top board to fix an Address Line connection for the Program ROMs to fix a stuck on crosshatch issue. Tested. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 08, 2021, 05:28:07 PM
Model: MV1B1
Symptom: Garbage on screen

Board was stuck on the green screen, indicating a Calendar error. Replaced a bad surface mount D4990AG IC and tested. Board was missing every other vertical line of pixels for the entire screen. Replaced a bad NEO-ZMC2 IC and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 08, 2021, 11:01:34 PM
Model: MV1FZ
Symptom: No audio

Board had attempted repairs done: Recapped, audio amp IC replaced, and the YM2610 IC replaced.

Found a dead trace on data line D4 on the YM2610 chip. Patched the trace and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 12, 2021, 09:26:05 PM
Model: MV4
Symptom: Battery damage

Cleaned the top and bottom PCBs. Replaced the board interconnects next to the battery for the top and bottom boards. Tested. Board had a Video RAM error at $8000. Patched battery damaged trace and tested. "Calendar error" - patched trace and tested. "Work RAM error" - patched another trace and tested. Board booted to a Crosshatch of Death. Patched 20 traces going to the 74AS245 and 74LS244 chips carrying the Program ROM signals. Tested. Still at the Crosshatch of Death. Repaired a trace between pins 19, 1, and 10, of a 74LS244 to restore the Enable signal to the 2 74AS245 chips on the data bus. Tested. Very faint audio. Installed a coin cell battery kit and new audio caps. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 20, 2021, 03:01:23 PM
Model: MV1FZ
Symptom: No audio

Colors were also very corrupt.

Replaced (an obviously) bad audio amplifier chip with a hole in it. Recapped the audio section and tested the audio. Replaced 8 blown surface mount resistors, 2 74LS245, 2 74LS273, and 1 bad 74LS05 chip in the video output section and tested.

With all the damage, it appeared the PCB was hooked up in a cabinet with a monitor that required an isolation transformer, but did not  have one. This resulted in power flowing back through the PCB damaging the video output section.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 20, 2021, 03:01:52 PM
Model: MV1FZ
Symptom: Reboots

Cleaned a very dirty edge connector and recapped PCB. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 24, 2021, 09:59:26 PM
Model: MV4
Symptom: No audio

Removed the battery. Cleaned top & bottom PCBs. Installed cap kit and coin cell battery kit. Board now had audio, but would not see cartridges. Replaced the board interconnects next to the battery. Tested. Games played but were missing sound effects. Replaced YM2610 and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 24, 2021, 09:59:58 PM
Model: MV4
Symptom: No audio

Removed battery. Cleaned top and bottom PCBs. Installed cap kit and coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 26, 2021, 09:11:05 PM
Model: Neo Geo MV1FZS
Symptom: Garbled sound

Cleaned the riser board and slots. Patched a dead trace to the cartridge slot on the riser board. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 14, 2021, 12:17:24 AM
Model: MV4
Symptom: Work RAM Error

Replaced bad work RAM and tested. No audio. Recapped PCB and tested. Board failed with video garbage during burn-in. Replaced bad surface mount video RAM and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 14, 2021, 08:51:15 PM
Model: MV2F
Symptom: No sound from carts

Board had test sounds. Resetting Backup RAM did not fix the error. Checked and verified trace continuity to the Sound Program ROM for both slots. Tested with a cartridge and found ROM Address A0 stuck low. Tested and found it shorted to ground. Replaced the NEO-E0 custom IC and tested cartridges successfully.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 17, 2022, 01:41:54 PM
Model: MV4
Symptom: Crashing while playing games.

Board had the battery replaced and several jumpers on normally battery damaged traces. Removed the wires to redo them properly and found all the traces were OK. Installed an audio cap kit to fix low audio issues. Cleaned the top board and patched a dead trace in the Video ROM section to fix lines on the screen on Slot 3. Board would still crash. Installed a UniBIOS chip and saw the crashes were in the vector table or Program ROM. The vector table is in each program ROM, so the issue was with reading the ROMs. Replaced the 2 74AS245 chips on the data bus connection to the ROMs and tested. The UniBIOS was doing strange things in that the buttons and sticks were all mixed up - pressing Up on the joystick would act as button C and reset the system. Reset Backup RAM, tested, reinstalled the original BIOS, reset the Backup RAM again, and successfully tested the system for several hours without a reboot.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 17, 2022, 01:48:26 PM
Model: MV4
Symptom: Stuck on crosshatch

Removed the battery and cleaned the leak damaged area. Removed the damaged board interconnect pair from the bottom and top PCB, cleaned under them, and replaced them. Patched one damaged trace on the bottom PCB and installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 20, 2022, 09:25:40 PM
Model: MV4
Symptom: Vertical band of dots down center-right of screen. Scratchy sounds.

The dots were like a hash pattern of missing dots on the screen. Replaced bad NEO-B0 custom chip to fix that issue. Replaced bad YM2610 to fix the sound issue. Installed coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 20, 2022, 09:26:46 PM
Model: Samurai Shodown II MVS Cartridge
Symptom: Kills sound when in the system.

Replaced a bad M1 Sound ROM and resoldered cracked joints on the video/sound cart board. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 20, 2022, 09:29:13 PM
Model: MV4
Symptom: RAM ERROR at 20D

Replaced bad surface mount Video RAM and tested to find low volume and missing FM sounds. Recapped the audio to fix the low volume. Replaced the YM2610 to fix the missing FM sounds issue. Slot 1 would not always recognize cartridges installed. Replaced the Program / Sound FX cart PCB slot on the Slot 1 pair and tested. Installed a coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 20, 2022, 09:33:52 PM
Model: MV4
Symptom: Video RAM error at 0000

Replaced bad SMT video RAM IC and tested. Video RAM error at 8000. Replaced bad DIP video RAM IC and tested. Audio was low. Replaced the audio caps and installed a coin cell battery kit. Tested. Top board had problems reliably reading cartridges. Cleaned the top PCB / slots and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 14, 2022, 07:45:23 PM
Model: MV4
Symptom: Will not boot carts in Slot 1.

Removed the fishpaper and foam from the bottom of the PCB as it was turning stiff and corroding pins. Patched a dead trace. Tested. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 14, 2022, 07:48:42 PM
Model: MV4
Symptom: Stuck on crosshatch

Board had a coin cell mod already done but the 470 ohm resistor wasn't removed.

Removed the 470 ohm resistor and tested. No audio. Recapped the audio section and no audio, but now there was normal audio hiss at full volume. Replaced bad YM2610 and tested. Board would boot slot 1 but not any cartridges in the other 3 slots. Cleaned the top board and repaired a broken trace for the clock signal to the 74LS174 that latched the slot selection via the 74LS138. Installed a customer requested UniBIOS 4.0 chip. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 19, 2022, 07:48:06 PM
Model: MV2
Symptom: Dead. Click of death.

Board had a soda spilled on it when in the cabinet.

Cleaned the PCB and replaced a bad BIOS ROM. Tested. Installed a coin cell kit, set the clock, and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 22, 2022, 08:03:41 PM
Model: MV4
Symptom: Crosshatch of death

Removed the NiCd battery and cleaned that area of the board. Patched one damaged trace. Tested. Replaced the audio caps to fix a low volume issue. Tested. Installed a coin cell kit and replaced 6 screws when reassembling. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on June 13, 2022, 11:29:46 PM
Model: MV2
Symptom: Palette RAM errors

Board had attempted repair damage and paste flux smeared all over the 2 RAMs.

Removed 2 Palette RAMs, cleaned up the flux, removed damaged sections of traces that were shorting, installed three Kynar jumpers to patch the traces, and installed sockets. Installed customer supplied Palette RAM. Text color was fixed, but the RAM still was showing as bad. Replaced bad NEO-B0 custom chip to fix the Palette RAM error. Installed a coin cell battery kit and tested. Player 1 left and right controls were stuck on. Replaced a bad resistor/capacitor filter network and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on June 27, 2022, 03:09:51 PM
Model: MV4
Symptom: Backup RAM B240 Error and Stuck on green errors.

Board had a clipped component lead under the fishpaper and foam insulation under the battery section causing the error. Removed the lead, removed the battery, removed the 470 ohm resistor. Cleaned under the battery and installed a coin cell battery holder. Removed a short between two caps while removing them. Recapped the audio section, including caps previously replaced by a prior tech. Tested the board.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on June 28, 2022, 01:49:35 PM
Model: MV4
Symptom: Click of Death

Board was very dead - Stuck in Watchdog with no activity on the enable line on the BIOS ROM. Checked address and data buses for shorts. Repaired a battery damaged trace off a 74LS05 to fix the issue. Installed a coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on June 30, 2022, 02:18:01 PM
Model: MV4
Symptom: Stuck on Crosshatch

Removed battery and cleaned under and around the area. Patched one trace and installed a coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on June 30, 2022, 02:19:05 PM
Model: MV4
Symptom: Crosshatch of death

Removed the battery and cleaned under and around it. Replaced the upper and lower board interconnects as they were badly battery damaged. Installed a coin cell kit. Removed 4 grossly oversized caps from the audio section and recapped the board. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 18, 2022, 07:50:58 PM
Model: MV2F
Symptom: Not working.

Removed leaking NiCd, cleaned that area of the PCB, then installed a coin cell kit. Cleaned the slots and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 18, 2022, 07:53:20 PM
Model: MV2
Symptom: Graphics issue with slot 2

Slot 1 was filled with corrosion. Removed both connectors for slot 1 from the PCB to discover a horror of corrosion under them. Removed the battery, cleaned the PCB thoroughly, replaced the bad slot connectors with 2 from a donor PCB, and patched 8 damaged traces. Tested. installed coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on August 21, 2022, 09:10:03 AM
Model: MV4
Symptom: Crosshatch of death (Will not boot cartridges)

Cleaned battery damaged area of the PCB and tested the usual traces for damage - all were good. The 2 74ALS245 data latches for the cartridge data had only one with a working /Enable pin. Replaced PRO-C0 IC, still dead. Found a corroded BIOS socket, replaced that and noticed a green pin on the 74ALS08 next to it. Removed and socketed that IC and patched a corrosion damaged trace under it. Board would boot cartridges but the colors and sounds were incorrect, low audio, and slot 2 had graphics issues. Installed a coin cell kit and audio cap kit. Patched a corroded trace between a 74LS273 and a ladder DAC resistor in the blue output circuit to fix the color issues. The rest of the issues were on the top board.

Cleaned the top PCB. Removed the hardened foam and fishpaper from under the PCB and patched a dead trace for Slot 2 causing lines in graphics. Patched another traces to address the remaining lines issue for slot 2. Patched a bad trace to the slot for the address lines to the graphics ROMs to fix an issue with incorrect graphics data being seen. Patched a dead trace to fix the audio samples playback corruption issue for all slots. Tested. Slot 1 had no audio. Patched a dead trace to the /Enable line of the 74LS246 latching the address data for the sound ROM. Tested. Patched a dead trace to the 74LS244 buffering an address line to the Sound ROM. Tested. All issues resolved.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on September 22, 2022, 02:01:11 PM
Model: MV1B
Symptom: Stuck on green

Replaced 2 broken 3.9K ohm SMT resistors on the bottom of the PCB. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 10, 2022, 03:18:58 PM
Model: MV1FS
Symptom: Dead. Black screen.

Sometimes boots to garbage, sometimes to a RAM Error.

Replaced bad upper Work RAM. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on November 12, 2022, 12:17:45 AM
Model: MV2
Symptom: Video RAM Error at $8000

Replaced bad CXK5814 SRAM, installed a coin cell battery kit, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 19, 2023, 09:29:30 PM
Model: MV4
Symptom: Crosshatch of death

Board was stuck on the crosshatch screen and would not read cartridges. Patched one battery damaged data and one damaged address line on the bottom board and 5 address lines on the top board for CPU access to the Program ROMs on the cartridges. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 21, 2023, 11:14:34 PM
Model: MV4
Symptom: Missing audio left channel

Board had input protection SIPs replaced with one from a Capcom game and 2 simple resistor packs. Replaced the three with the proper ones for the board. Recapped the audio section. Installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 16, 2023, 07:10:38 PM
Model: MV4
Symptom: Slot 4 not working

Patched a dead trace on the slot selection circuit between the 74LS138 and the grouping of 74LS245 chips on Slot 4. Tested. Replaced bad audio caps and installed a coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 06, 2023, 06:14:38 PM
Model: MV2F
Symptom: No audio

Recapped audio section. Replaced NiCd battery with a coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 10, 2023, 12:32:29 AM
Model: MV2
Symptom: Stuck at crosshatch

Board had a 1/3AA lithium battery installed as a backup battery.

Tested the battery and it was dead. Removed the battery. Removed 2 slot connectors and cleaned spill that had hardened under it. Patched one trace at a via under one of the slot connectors to restore Program ROM address line A3. Cleaned up one slot connector and reinstalled it. Replaced the 2nd slot connector. Board was still stuck on crosshatch but all signals were now present. Lifted multiple bent component pins and traced out 10 scratched and gouged traces. Patched one trace and tested. Installed coin cell kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 10, 2023, 12:34:04 AM
Model: MV2F
Symptom: Z80 Error

Board had a lithium 1/3AA installed for a backup battery.

Clipped the 470 ohm resistor out of the charging circuit to keep the PCB from recharging the lithium battery as that is very dangerous. Board was missing the 6116-10 Sound RAM chip. Installed a 24 pin narrow socket and a replacement RAM chip. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 10, 2023, 10:21:59 PM
Model: MV4
Symptom: Will not read memory card

Replaced bad 74HCT244 at location 9A and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 27, 2023, 09:07:58 AM
Model: MV2F
Symptom: Graphic corruption

Removed battery damaged NEO-ZMC2 chip, cleaned up the pads on the board, and installed one from a donor board. Patched 3 dead signal traces with Kynar wire. Patched a dead power connection to the chip. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 29, 2023, 03:33:55 AM
Model: MV1FT
Symptom: Z80 Error

Note: Board had the Z80 already replaced.

Checked the area between the backup battery and the YM2610 for the typical trace damage and found none. Checked the previous tech's work and found that Address line A2 did not have continuity between the M1 ROM and the CPU. Patched the trace with some Kynar wire and tested. Removed the battery and installed a coin cell kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 29, 2023, 03:35:40 AM
Model: MV1FT
Symptom: Z80 Error

Found the typical trace damage between the battery and the YM2610 sound chip. Cleaned the area, patched the traces carrying data lines D0, D1, and D2 for the sound subsystem past the battery area and tested. Installed a coin cell kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on March 29, 2023, 09:23:52 AM
Model: MV2-01
Symptom: Graphic corruption

Patched 2 battery damaged traces to the NEO-ZMC2 chip and tested. Found audio ADPCM sample data sounded very corrupt. Patched 2 battery damaged traces in the audio circuit and tested. Installed a coin cell battery kit and retested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 04, 2023, 03:48:10 PM
Model: MV4
Symptom: Graphic corruption on slot 4

Board had a poorly installed audio cap job done on it.

Cleaned hardened foam and fish paper from the bottom of the top board. Patched corroded trace from slot to the 74LS253 at F3, pin 3. Removed and reinstalled all the audio caps. Replaced 2 100uf caps that had physical damage and 3 470uf and 1 220uf caps that were not replaced by the previous tech. Now the caps were sitting low enough to fit under the top board without shorting where the fish paper and foam was removed. Installed coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 06, 2023, 03:15:09 AM
Model: MV1
Symptom: Cust requests test & recap

Recapped PCB and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 06, 2023, 03:16:11 AM
Model: MV2
Symptom: Cust requests test, UniBIOS, & recap

Replaced damaged memory card slot. Installed audio caps, installed UniBIOS 3.3, and replaced missing hardware. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on April 06, 2023, 03:16:50 AM
Model: MV2
Symptom: Backup RAM Error

Cleaned PCB. Replaced 74HC32 and upper Backup RAM. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 08, 2023, 08:37:29 PM
Model: P.O.W. (Prisoner of War)
Symptom: Stuck in test mode

Board was missing 20L10 PAL at A6. Replaced with a GAL22V10 programmed with code from the PLD Archive. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 22, 2023, 01:38:27 PM
Model: MV2F
Symptom: Graphic corruption

Removed leaking battery, cleaned up battery leakage. Patched multiple traces and tested. Replaced bad NEO-ZMC2 chip and retested. Installed coin cell battery kit and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on October 23, 2023, 12:11:00 AM
Model: MV4
Symptom: Low audio

Removed battery and 470 ohm resistor, installed a coin cell kit, and recapped the audio section. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 04, 2023, 01:56:50 AM
Model: Neo Geo MV4
Symptom: Unknown. Not listed.

Board arrived with a Diagnostic BIOS set installed and the 74LS86 chip replaced.

Ran the Diagnostic BIOS set and all tests passed. Removed the ROMs and installed regular ones. Board would not see cartridges. Repaired 2 battery damaged traces but the board still would not see the carts installed. Found the enable pins on the 74ALS245 data bus latches stuck high. Replaced a shorted 74ALS08 at C7 and a shorted 74ALS244 at C11 to fix that issue. Board would boot but had distorted sounds on the right channel. Replaced bad YM2610 and installed a coin cell battery kit to finish the repair.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on December 04, 2023, 10:18:31 PM
Model: Neo Geo MV4
Symptom: Intermittent crashes

Board had attempted repairs done and a UniBIOS 3.1 installed.

Removed 6 ribbon cable bodge wires from battery damaged area. Replaced the battery damaged 64-pin connectors on the top and bottom board. Placed 6 kynar bodge wires and tacked them into place. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on January 11, 2024, 02:28:30 PM
Model: Neo Geo MV4
Symptom: RAM ERROR

Board had an error in the upper Work RAM. Replaced the IC and tested, extremely low audio. Recapped the audio section and installed a coin cell battery kit. Tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 09, 2024, 10:50:02 PM
Model: MV4
Symptom: Video RAM error

Reflowed a badly replaced SMT Backup RAM and Video RAM. Slots 3 and 4 would not work. Deep cleaned top PCB / Slots, replaced missing/broken hardware, and tested.
Title: Re: SNK Games (Neo Geo MVS/AES)
Post by: channelmaniac on February 09, 2024, 10:51:45 PM
Model: MV4
Symptom: Work Ram Error

Replaced bad Work RAM at J8. Installed coin cell battery kit. Tested. Audio was about 30% low. Replaced audio caps and retested with carts. Patched dead trace on Slot 4 causing lines in video. Tested.
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