Author Topic: SNK Games (Neo Geo MVS/AES) (Read 125878 times)

channelmaniac · « **Reply #360 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.

channelmaniac · « **Reply #361 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.

channelmaniac · « **Reply #362 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.

channelmaniac · « **Reply #363 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.

channelmaniac · « **Reply #364 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.

channelmaniac · « **Reply #365 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.

channelmaniac · « **Reply #366 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.

channelmaniac · « **Reply #367 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.

channelmaniac · « **Reply #368 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.

channelmaniac · « **Reply #369 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.

channelmaniac · « **Reply #370 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.

channelmaniac · « **Reply #371 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.

channelmaniac · « **Reply #372 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.

channelmaniac · « **Reply #373 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.

channelmaniac · « **Reply #374 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.

channelmaniac · « **Reply #375 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.

channelmaniac · « **Reply #376 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.

channelmaniac · « **Reply #377 on:** January 08, 2021, 11:03:59 PM »

Model: MV1
Symptom: Garbled Screen

Cleaned riser/slot PCB and installed coin cell battery kit. Tested.

channelmaniac · « **Reply #378 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.

channelmaniac · « **Reply #379 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.

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Author Topic: SNK Games (Neo Geo MVS/AES) (Read 125878 times)