SNK Games (Neo Geo MVS/AES)

[channelmaniac]

Model: MV4
Symptom: Video RAM Error

Boards arrived oily and filthy. Cleaned top and bottom PCBs and slots. Replaced 1 bad 62256 SRAM in video section and tested. Recapped the audio section and installed a coin cell battery kit. Tested. Replaced one cross-threaded screw, 4 missing feet, and 3 incorrect screws when reassembling.

[channelmaniac]

Model: MV1FZ
Symptom: Squealing noise from monitor and garbage on screen

Cleaned crusty edge connector and replaced a badly corroded 24MHz main system clock crystal. Tested.

[channelmaniac]

Model: Neo-Geo MV1b
Symptom: Backup RAM Error 0x02 5555 5155

Replaced upper backup RAM. Board tossed out a lower Backup RAM error. Replaced lower Backup RAM. Board tossed out a boundary error of 0x00 5555 0055 - Control signals not correct on the Backup RAM. Found the Upper Backup RAM's R/W signal was stuck high. Replaced bad 74HC32 in the battery backup circuit and retested.

[channelmaniac]

Model: MV4
Symptom: Boots to crosshatch

Top board/slots were filthy. Cleaned top PCB and board would boot carts just fine, but rendered text screens and the FBI Warning screen were distorted. Replaced bad FIX ROM and tested. Replaced bad audio caps and left channel was still out on both headphones and standard audio out. Replaced bad LM324 to fix headphones issue and volume pot to fix standard audio out issues. Installed coin cell kit and tested. Slot 4 had lines in graphics. Patched dead trace on top PCB and tested.

[channelmaniac]

Model: MV4
Symptom: RAM ERROR $8000 Read: FF55

Replaced the upper Sprite RAM (DIP CXK5814-35) and tested. Board would not boot cartridges. Patched dead trace under a 74LS245 on the top PCB and tested. Replaced battery with a coin cell kit and tested.

[channelmaniac]

Model: MV4
Symptom: Crosshatch of death

This one had been worked on before and had a dead trace under the battery patched. A second trace went bad and was patched. Tested.

[channelmaniac]

Model: MV1F
Symptom: Z80 Error

Replaced the surface mount Z80 chip and tested. Replaced broken volume pot and retested.

[channelmaniac]

Model: MV1
Symptom: Graphic corruption

Cleaned slots. Removed leaking battery and cleaned up that area of the PCB. Installed a coin cell battery kit and patched 4 dead traces to the DIP switches. Replaced battery damaged 22pf capacitor on the clock/calendar crystal. Tested.

[channelmaniac]

Model: MV4
Symptom: Crosshatch of death

This one was an interesting one. Traces were all good and almost untouched, but the connector to the top board had corrosion damage on the pins. Replaced upper and lower PCB connector and tested.

[channelmaniac]

Model: MV4FT
Symptom: Dead. Severe battery damage

Patched the control lines and enable lines for the 74AS245 chips controlling the data bus to the upper PCB. Patched traces for missing /RESET, /AS, and R/W on the 74AS245 chips near the battery. Board booted to a Green Screen of Death - Clock/Calendar issue. Patched 3 dead traces between the clock/calendar chip and the NEO-F0 chip. Patched missing signal for SYSTEM and SYSTEMB. Replaced corroded BIOS socket. Patched a few more misc dead traces. Board would then boot to a Calendar Error screen and UniBIOS chips would not boot. Diagnostic ROM showed everything was good.

Pressed ABCD on boot to access the Diagnostic ROM menu. The Clock/Calendar test showed correct on the 1Hz setting but on the other 2 faster settings, the system was missing pulse counts. Started verifying all control signals on the 68000 CPU and found IPL0 and IPL1 dead. Patched those two traces and then all tests passed successfully and system would play games.

[channelmaniac]

Model: MV1FZ
Symptom: Loud noisy audio

Replaced bad volume control and recapped PCB. Game would boot but had no audio. Cleaned the slot PCB board interconnect connectors and tested.

[channelmaniac]

Model: MV4
Symptom: Check for battery damage

No problem found. Customer wanted board capped and a coin cell installed. Replaced the audio caps and installed a coin cell kit. Tested.

[channelmaniac]

Model: MV1
Symptom: Backup RAM Error

Pulled the cart slot PCB from the main board, cleaned up battery damage, replaced 2 bad Backup RAM chips, and tested. Stuck on green. Replaced battery damaged clock crystal and both attached capacitors. Tested. Patched 3 battery damaged traces to the DIP switches and installed a coin cell battery kit. Plugged the cart slot PCB back in and power supply would not start. Support bracket on the back of the PCB assembly was upside down and shorting all the soldered pins on the interconnections. Reinstalled support bracket and tested. Cleaned the edge contacts on the customer supplied cartridge and tested.

[channelmaniac]

Model: MV2
Symptom: Click of death

Flipped on all DIPs and board tried to boot into Work RAM Test loop, but stopped with a Backup RAM error B240. Patched dead trace on pin 11 of the 74HC32 in the backup battery area. Tested.

[channelmaniac]

Model: MV2
Symptom: Dead. Click of death.

Replaced 2x 74HC32 and an 74HC157 that were battery damaged. Replaced bad NEO-G0 chip that was shorting the data bus. Replaced both Backup RAM chips that failed diagnostic ROM checks. Board would now boot but had severe graphic corruption. Replaced NEO-ZMC2 chip and patched one dead trace. Game now booted and ran, but had vertical lines in graphics. Replaced bad NEO-257 chip and board would boot and play from slot 1 but had some vertical line corruption on slot 2. Replaced the other NEO-257 chip then installed a coin cell battery kit to finish the repair.

[channelmaniac]

Model: MV4F
Symptom: Will not play carts. Stuck on crosshatch.

Removed corroded battery. Cleaned PCB. Removed 470 ohm resistor to disable charging circuit. Patched five dead traces and replaced 2 corroded ferrite filters. Installed coin cell battery and tested.

[channelmaniac]

Model: MV4
Symptom: Will not play carts. Stuck on crosshatch.

Note: Board had an oily substance on the top PCB and in the slots.

Removed battery and cleaned under it. Removed the 470 ohm resistor to disable the charging circuit. Patched one dead trace. Cleaned the top PCB and tested. Warned customer to clean their cartridges before inserting them into this PCB as they will have that oily stuff on their contacts.

[channelmaniac]

Model: MV4
Symptom: Click of death. Black screen.

Flipped all DIPs on to attempt to put it into RAM test and was successful. Backup RAM 0D000000 Written 5555 Read 5532. Lower Backup RAM had a missing R/W signal. Patched dead trace and tested.