SNK Games (Neo Geo MVS / AES)

[channelmaniac]

Model: MV2F
Symptoms: Vertical lines on both slots

Board had a leaking battery. Cleaned up the battery corrosion and jumpered 2 traces between the NEO-257 and the NEO-ZMC2 ICs to fix slot 1. Jumpered a bad trace between slot 2 and the NEO-257 IC to fix slot 2. Installed a new battery and tested.

[channelmaniac]

Model: MV4
Symptom: Low audio, replace battery

Customer requested battery change. Installed cap kit and battery. Tested.

[channelmaniac]

Model: MV2F
Symptom: Low audio on one channel and lines on screen

Battery was leaking. Removed battery, cleaned board, and installed cap kit to fix audio issue. Replaced bad NEO-257 IC to fix lines on screen. Installed new battery and tested.

[channelmaniac]

Model: MV1
Symptom: Backup RAM Error

Board had a Backup RAM Error at D0000, Written 0000, Read 04D0. Replaced bad 74HC32 chip controlling the enable lines. Board then gave a Backup RAM error at D0008. Replaced one 62256 SRAM chip and tested. Board had no audio. Replaced 2 physically broken 470uf @ 16v caps to finish the repair.

[channelmaniac]

Model: MV4
Symptom: Work RAM Error

Replaced bad SRAM at location G9 and ran self tests. Audio level was low. Installed audio cap kit and tested. Board would not read any carts. Replaced a corroded 74LS244 on the top board, cleaned the rodent damage, and patched 2 traces. Tested.

[channelmaniac]

Model: MV1
Symptom: Work RAM Error: Written AAAA Read: AA2A

Replaced the SRAM at location H3 and tested.

[channelmaniac]

Model: MV6
Symptom: No Audio

Board had very faint audio when running hardware test. Recapped board and tested. Board had strong audio in test mode but no audio for games. Reset backup RAM and tested. Corrupt backup RAM was causing the audio to not work.

[channelmaniac]

Model: MV4
Symptom: Very low audio

Installed audio cap kit and tested.

[channelmaniac]

Model: MV4
Symptom: Low Audio

Installed Cap Kit and tested.

[channelmaniac]

Model: MV4
Symptom: Low Audio

Board would not play hardware test tones. Game audio worked, but was low. Installed cap kit to fix audio levels. Replaced bad SM1 ROM to fix the hardware test tones.

[channelmaniac]

Model: MV4
Symptom: Crosshatch of death

Removed leaking battery and cleaned board. Repaired 12 bad traces and tested.

[channelmaniac]

Model: MV1
Symptom: Tinny sounding audio

Cleaned the stereo/mono switch and replaced a bad battery that had started to leak. Tested.

[channelmaniac]

Model: MV1
Symptom: Stuck on Green

Board had the battery already removed and had minimal corrosion damage but still had the crystal and D4990 clock chip with some on it. Cleaned the corrosion, including some bridging the crystal's leads and tested the board. The corrosion bridge caused the crystal to not oscillate. Replaced the missing battery and tested.

[channelmaniac]

Model: MV1
Symptom: Z80 Error

Board was labeled Z80 error but had multiple issues caused by battery leakage, attempted repairs, and rodent damage. Removed an extra Z80 CPU from the BIOS socket and installed the correct BIOS chip. Removed leaking battery, cleaned board, and replaced crystal to fix calendar error. Patched a bad trace going to the cartridge port. Z80 Error had 2 causes. The first was a corroded trace between the NE0-D0 chip, pin 40 and NE0-B0 pin 41. The Z80 Error returned during testing and the IRQ pins on the CPU had bad signals. Pins 36 and 37 on the NE0-D0 read 50 ohms between them. This drove the NMI and IRQ lines for the Z80 CPU. Removed the NE0-D0 IC, cleaned the rodent damage under it, and reinstalled it and the patch to the B0 chip. Tested.

The rodent damage corroded the solder on the plated thru holes under the NE0-D0 IC. This corrosion was bridging the 2 pads causing the problems.

[channelmaniac]

Model: MV4
Symptom: Constantly reboots with Calendar Error

System was odd in that it would come up with a Calendar Error message then reboot. The reboot was odd since the system should've stayed on the Calendar Error screen. Disassembled system only to find that it worked fine. Tapping the board caused the problem to intermittently return. Resoldered bad connections on the surface mount Work and Backup RAM to fix.

[channelmaniac]

Model: MV4
Symptom: Locks up in Attract mode. Sounds stop working at times. Won't keep high scores.

Replaced bad battery to fix score issue. Board would reboot if carts bumped or jiggled. Cleaned the top board and slots then tested.

[channelmaniac]

Model: MV4
Symptom: No sound

Reset backup RAM and then had low volume on right channel and no audio on left. Installed audio cap kit. Replaced leaking battery. Cleaned top board and slots then tested.

[channelmaniac]

Model: MV4
Symptoms: Carts won't play and Z80 Error

Cart in slot 1 wouldn't play and in slot 2 gave a Z80 Error. Board was described as having "shipping damage" and the battery came off from the spot welded leads and bounced around between the boards.

DIP switch 8 was on. This is the 'pause' switch which caused the game to freeze upon booting and not play any carts. The Metal Slug cart shipped with the board was dirty. This was causing the Z80 Error. Playing with test carts showed the system had garbled sound effects. No traces were damaged. Swapped out the 74LS244 and 245 chips buffering the sound data. No change. Replaced the YM2610 sound chip to fix the sound issue and tested. Cleaned the Metal Slug cart and tested.

Per customer, replaced the battery and missing screws. Replaced 1 PC board standoff that had crossed threads.

[channelmaniac]

Model: MV4
Symptom: Video RAM Error $8000, Written 5555 Read 0055

Replaced bad SRAM IC and tested. Board had low audio. Installed audio cap kit to fix audio issue. Cleaned top board & slots. Replaced 2 missing screws, 2 stripped screws, a broken standoff, and a broken mounting foot. Tested system.

The standoff and foot were broken due to insufficient packing in the box.

[channelmaniac]

Model: MV6
Symptom: No audio

Could not put board on bench without first contacting customer. The NiCd battery on the board was replaced by a NON-rechargeable lithium battery and the charging circuit was NOT disabled. This was dangerous.

Replaced battery with a NiMH rechargeable type, installed Audio Cap Kit, and tested. Replaced one incorrect standoff and reassembled system then retested.

[channelmaniac]

Model: MV-2
Symptom: vertical lines in game

Board had a leaking battery that caused trace damage. Jumpered 2 bad traces between the NE0-ZMC2 and the NE0-257 IC, replaced the bad battery, and tested.

[channelmaniac]

Model: MV-2F
Symptom: Video RAM Error

Video RAM ERROR $8000, Written 5555, Read FFFF

Replaced both CXK-5814 SRAM chips. Tested board. Replaced leaking backup battery and tested again.

[channelmaniac]

Model: MV4
Symptom: Garbled graphics and text

The top board had corrosion damage from either a liquid spill or rodent urine. Removed 2 74LS245 and 5 74LS244 chips from the top board. Cleaned the board and checked for trace damage. Installed new chips, repaired 3 traces, and tested board.

[channelmaniac]

Model: MV4
Symptom: Video RAM Error

Video RAM Error $00000005 Write 5555 Read 5557

Replaced bad SRAM IC at K9 and tested.

[channelmaniac]

Model: MV4
Symptom: Crosshatch of death

Board had a leaking battery but the traces were still OK. Removed the battery & cleaned the residue. Tested traces and found no bad ones. The 74LS138 on the upper board that selects the slots had no signal on pin 4. Replaced bad 74AS244 on the bottom board. All traces were good and all address lines to the carts were good but the system still would not read the carts. Replaced 2 74AS245 ICs interfacing the cartridge data lines on the bottom board and tested carts in all 4 slots.