Author Topic: SNK Games (Neo Geo MVS/AES) (Read 127247 times)

channelmaniac · « **Reply #380 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.

channelmaniac · « **Reply #381 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.

channelmaniac · « **Reply #382 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.

channelmaniac · « **Reply #383 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.

channelmaniac · « **Reply #384 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.

channelmaniac · « **Reply #385 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.

channelmaniac · « **Reply #386 on:** February 04, 2021, 11:57:45 PM »

Model: MV4FT
Symptom: Garbled audio

Replaced YM2610 audio chip and tested.

channelmaniac · « **Reply #387 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.

channelmaniac · « **Reply #388 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.

channelmaniac · « **Reply #389 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.

channelmaniac · « **Reply #390 on:** February 14, 2021, 09:41:00 AM »

Model: Time Soldiers
Symptom: No sound

Replaced missing Z80B CPU and tested.

channelmaniac · « **Reply #391 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.

channelmaniac · « **Reply #392 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.

channelmaniac · « **Reply #393 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.

channelmaniac · « **Reply #394 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.

channelmaniac · « **Reply #395 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.

channelmaniac · « **Reply #396 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.

channelmaniac · « **Reply #397 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.

channelmaniac · « **Reply #398 on:** September 30, 2021, 09:18:43 PM »

Model: MV2
Symptom: Backup RAM Error

Replaced both backup RAM chips and tested.

channelmaniac · « **Reply #399 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.

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Author Topic: SNK Games (Neo Geo MVS/AES) (Read 127247 times)