Author Topic: Midway Games (Read 103405 times)

channelmaniac · « **Reply #300 on:** May 11, 2019, 11:24:43 PM »

Model: Ms Pac
Symptom: Dead

Replaced 3 large wire jumpers with Kynar wire and bridged 2 broken traces between the CPU and ROMs. Reinserted a backwards RAM chip and tested. Luckily the RAM was not damaged.

channelmaniac · « **Reply #301 on:** May 11, 2019, 11:28:20 PM »

Model: Ms Pac Man
Symptom: Distorted blue screen and intermittent boot

Replaced 74LS161 at 3R to fix distortion. Replaced bad PROM at 7F to fix blue screen issue. Tested. Replaced bad socket at 4K to fix boot issue. Tested. Board output the wrong colors on the screen - they looked like pastels. Removed short from pin 9 of the PROM at 4A and retested. Replace bad 74LS86 at 4F as the output did not follow the input and was causing the PROM at 3M to output data at the wrong time. Tested.

channelmaniac · « **Reply #302 on:** May 12, 2019, 04:34:18 PM »

Model: Ms. Pac Man
Symptom: Dead

Previous tech replaced the CPU and Sync Buss Controller sockets.

Looked over the board and discovered the tech didn't finish soldering all the pins on the CPU socket. Finished soldering the CPU chip and checked continuity to see what the tech messed up. Jumpered a bad trace on Data line D1 from the Sync Buss Controller to the CPU and from the CPU to the edge connector.. Game would boot from a ROM attached to the edge connector, but not from row 6. Replaced bad 74LS42 decoder IC driving the chip enables and tested. Game played but had dots on the screen. Reprogrammed the character ROM at 5E as it had suffered from bit rot. Patched a burned trace to the edge connector and tested game.

channelmaniac · « **Reply #303 on:** May 15, 2019, 06:19:54 PM »

Model: Space Invaders Deluxe
Symptom: Dead

Replaced 74161 and 7442 (address decoder) ICs, 4 ROM sockets, and the CPU socket. Board would boot but would crash immediately and reboot. Installed a missing ROM at D1 and tested. Board played but was missing the explosion sound. Replaced a bad LM3900 at K3-4 and tested.

channelmaniac · « **Reply #304 on:** June 02, 2019, 03:05:49 PM »

Model: Midway 8080 Motherboard
Symptom: Dead

Replaced missing 74LS00 at BX and tested

channelmaniac · « **Reply #305 on:** June 02, 2019, 03:07:51 PM »

Model: Midway 8080 Motherboard
Symptom: Dead

Replaced bad 74LS00 at B6 and 4 bad LS08 at H3, G3, F3, and F2. Tested.

channelmaniac · « **Reply #306 on:** June 02, 2019, 03:09:54 PM »

Model: Midway 8080 Motherboard
Symptom: Dead

Replaced 74166 at C4 and 4 10uf capacitors. Replaced 2 74LS 08 at H3 and F2. Replaced 7442 at E2 and tested.

channelmaniac · « **Reply #307 on:** June 02, 2019, 03:11:05 PM »

Model: Midway 8080 Motherboard
Symptom: Dead

Replaced dead CPU. Replaced bad 74LS157 at F4. Tested.

channelmaniac · « **Reply #308 on:** June 02, 2019, 03:15:35 PM »

Model: Midway 8080 Motherboard
Symptom: Dead

Replaced dead 74LS174 at A3, C3, and D7. Replaced corroded blue CPU socket with a standard dual wipe. Looked at memory outputs and getting strange results. Replaced chattering 74LS04 at D4 and E4. Address lines were still not quite correct. Replaced bad 74LS161 at D5 to fix. The data bus was still locked on a bit to the CPU and a bit to the RAM - Replaced the 8216 bus latches at B3 and D3 to fix. Tested and burned in board.

channelmaniac · « **Reply #309 on:** December 25, 2019, 10:44:12 PM »

Model: Pac Man
Symptom: Random reboots

Board was true to the description and would randomly reboot. Cleaned dirty CPU pins and tested. Nope. Fixed cracked solder joints on the Z80 Sync Buss Controller. Nope. Checked the 161/163 clock dividers, sync buss daughterboard, VRAM Addresser daughterboard, and program ROMs by substitution - nope. Dug deeper into the CPU circuit and checked the /NMI, /IRQ, and /RESET lines. All were good and it wasn't a watchdog reset. Checked the CPU clock and found it was very distorted sounding on the logic probe. Replaced the 74LS368 in the clock circuit and successfully tested the game.

channelmaniac · « **Reply #310 on:** December 27, 2019, 04:07:14 PM »

Model: Ms Pac Man
Symptom: Burnt edge connector

Repaired edge connector. Game would not boot. Repaired broken leg on ROM at 6H. Game would boot but there were no moving sprites on the screen. Replaced bad 74LS161 at 1E and tested.

channelmaniac · « **Reply #311 on:** December 27, 2019, 04:08:52 PM »

Model: Ms Pac Man
Symptom: Flashing 1 on screen. Remove operator hack.

Removed the operator hack and installed a replacement 74LS74 and socket at 8C as it was modified for the hack. Replaced missing ROM at 6F to fix the flashing 1 error. Tested.

channelmaniac · « **Reply #312 on:** December 27, 2019, 04:22:30 PM »

Model: Pac Man
Symptom: Stuck in boot loop

Pulled ROMs and used an external 6-in-1 ROM to test. Board booted the menu but was missing characters. Replaced bad RAM at 4P and tested. Reinstalled ROMs on Row 6 and tested.

channelmaniac · « **Reply #313 on:** March 08, 2020, 07:13:01 PM »

Model: Pac Man
Symptom: No Sync

Replaced bad 74LS161 at location 2R and tested. Pin 15 of 2R (Carry) was stuck low causing the LS161 at 2S to have no output.

channelmaniac · « **Reply #314 on:** April 09, 2020, 10:45:59 PM »

Model: Rally-X
Symptom: Dead

It had the orange socket for the Sync Bus Controller IC and the IC had weak legs. Tap it and the game would try to boot. Pulled it and two legs bent over, barely hanging on. Soldered it to a machine pin socket to save it then reinserted it back into the socket.

Board would then try to boot but had corrupt graphics on the screen and would reboot if you tapped the mask ROMs on the CPU board. Replaced all the mask ROMs with 2532 EPROMs.

Game was now stable but had corrupt text and border graphics. Found the 2532 on the video board had pin 18 (/CE) stuck high. Traced it back to a broken connection on pin 44 (5th from the end on the middle connector) of the wire harness. Replaced the broken connector and tested.

channelmaniac · « **Reply #315 on:** April 27, 2020, 10:55:31 PM »

Model: Midway Y-Unit
Info: Pinout for custom U99 IC

Had a board to repair that was a major ordeal... and while working on it I had to figure out why U99 was showing as bad, when it was not. Pinned out the IC based on the schematic, a multimeter for power/ground pins, and trace following. Hope you find it helpful.

channelmaniac · « **Reply #316 on:** April 28, 2020, 10:45:31 PM »

Model: Trog
Symptom: Dead

Board had some very strange repair work done using enamel coated magnet wire covered in silicone caulk.

Board was stuck in watchdog. Found pin 17 of one 4464 DRAM shorted to +5v. Tracked it down to a bypass capacitor lead pushed against the board and shorting to the trace. Fixed that. The board would boot to a U99 error, no voice/DAC sound, corrupt graphics, and bad colors. Traced out connections, they were all good. Tracked down the U99 error and part of the graphic corruption to an issue that would come and go when the board was flexed. Narrowed it down to a small area under the silicone.

Removed all the silicone and magnet wires. Straightened up multiple bent chip legs and installed much shorter Kynar wire jumpers to fix the U99 error. Replaced a corroded CPU socket then removed extraneous video RAM from the sockets on the board to fix the color issues. Replaced the axial caps and 4 1458 Op Amps to restore all sounds. Tested.

channelmaniac · « **Reply #317 on:** May 22, 2020, 09:31:06 AM »

Model: Space Invaders
Symptom: Dead. Flickering screen

Cleaned tarnished pins on a socketed 74160 in the clocking circuit to fix the flickering. Fixed a bent pin on ROM E causing the ground pin to not make contact. Tested.

channelmaniac · « **Reply #318 on:** June 04, 2020, 06:40:44 PM »

Model: Ms Pac Man
Symptom: Dead

Replaced shorted Sprite RAM at 2A and 2B, bad 74LS161 clock dividers at 3R and 3S and bad 74LS368 clock driver IC at 8B. Tested. Board would not boot. Replaced bad 74LS139 on the Sync Bus Controller and tested.

channelmaniac · « **Reply #319 on:** June 07, 2020, 06:38:15 PM »

Model: Mortal Kombat 3
Symptom: ROM errors, garbage on screen.

Cleaned multiple corroded ROM legs. Repaired a rusted off leg on one EPROM. Reprogrammed 3 ROMs to resolve their errors. Repaired 2 gouged traces to finish the ROM error repairs. Patched a corroded trace to fix the graphic corruption issues. Replaced bad TL084 op-amp in the audio output circuitry to restore sound.

News:

NLG Site Navigation Menu

Author Topic: Midway Games (Read 103405 times)