Author Topic: SNK Games (Neo Geo MVS/AES) (Read 127791 times)

channelmaniac · « **Reply #400 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.

channelmaniac · « **Reply #401 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.

channelmaniac · « **Reply #402 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.

channelmaniac · « **Reply #403 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.

channelmaniac · « **Reply #404 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.

channelmaniac · « **Reply #405 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.

channelmaniac · « **Reply #406 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.

channelmaniac · « **Reply #407 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.

channelmaniac · « **Reply #408 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.

channelmaniac · « **Reply #409 on:** November 20, 2021, 03:01:52 PM »

Model: MV1FZ
Symptom: Reboots

Cleaned a very dirty edge connector and recapped PCB. Tested.

channelmaniac · « **Reply #410 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.

channelmaniac · « **Reply #411 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.

channelmaniac · « **Reply #412 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.

channelmaniac · « **Reply #413 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.

channelmaniac · « **Reply #414 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.

channelmaniac · « **Reply #415 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.

channelmaniac · « **Reply #416 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.

channelmaniac · « **Reply #417 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.

channelmaniac · « **Reply #418 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.

channelmaniac · « **Reply #419 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.

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Author Topic: SNK Games (Neo Geo MVS/AES) (Read 127791 times)