SNK Games (Neo Geo MVS / AES)
channelmaniac:
Model: MV4
Symptom: Low audio and missing sounds
Installed an audio cap kit to restore sound and noticed that the sound effects for spelling the bonus word in Shock Troopers, 2nd Squad was missing. In Metal Slug the bonus sound from picking up fruit or other non-gun objects was missing.
Replaced a bad YM2610 IC and tested.
channelmaniac:
Tip: Neo-Geo Cartridge ROM Functions:
P: Program ROMs
P1 is typically the main program ROM, it can be up to 8M and contains the entire game logic.
Some old PROG boards use 2/4M ROMs so P2-4 can be the rest of the P1 address space.
Then there's another address range used for a few different things such as the link circuitry, Fatal Fury 2 protection and later on it became used for another 8M+ of program ROM. ROMs mapped here are SP2 (P2 on the chip) if P1 is 8M.
EP1 replaces P1 with updated program code.
EP2 can be either the second half of EP1 if they're both 4M or can be the same thing as SP2 (8M+).
V are YM2610 ADPCM data ROMs.
There are actually two types of V ROM, one for the low frequency channel, one for the high. Games quickly started containing a chip called NEO-PCM which allows both channels to use the same ROM.
C ROMs only contain sprite data (which also makes up the backgrounds on the Neo), not the fixed tile layer data.
M ROM contains the Z80 sound engine program as well as the actual "track" sequences. Remember all sample data however is contained in the V ROMs.
S aka the "FIX" layer ROM contains the fixed (non-scrollable) tilemap layer that overlays sprites. Life/POW bars are made of this.
Thanks to Calpis on the Assemblergames.com forum for this info!
channelmaniac:
Model: MV4
Symptom: RAM Error, written AAAA read A8AA
Board was shipped in a box that didn't allow for sufficient packing. 2 standoffs and the top cover were bent.
Replaced 1 bad SRAM IC at location H9, installed an audio cap kit, replaced 2 bent standoffs, and fixed the bent top cover. The audio is now loud and crisp.
channelmaniac:
Model: MV4
Symptom: Stuck in watchdog. Customer requested a UniBIOS upgrade and a new battery be installed.
Repaired 3 broken traces. Tested board and found the audio level was low. Recapped the board to fix the audio problem. Replaced the battery and upgraded the system with a UniBIOS 3.0 chip.
channelmaniac:
Model: MV4
Symptom: Backup RAM Error
Replaced bad surface mount SRAM IC and tested.
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