I recently acquired a cheap Top Hunter MVS cartridge with graphic glitches for repair. When I plugged it into my Neo Geo MV2FS, it had the mentioned graphic glitches and a mostly green-tinted image.
I took the cartridge apart and had a look at the PCBs: No obvious damages or broken traces.
Then, I cleaned the contacts with DeoxIT and tried the game again. But unfortunately, nothing had changed. A quick search on Google recommended to check and change the C ROMs on the CHA256B PCB – which meant a lot of work. Before I went on with this task, I tried the “GameCart CRC Check” of the Universe BIOS.
And there was finally a clue about what could be wrong: One of the program ROMs showed CRC32 4BEA7001 which means either unknown or bad. The expected value of the P ROM 046-p2.sp2 is F182CB3E (cross-checked with a NeoSD cartridge and tophuntr).
Again, I had a close look at the PROGTOP PCB, especially at ROM 046-P2 in the upper right corner. And again, there was no visible damage. Just in case, I renewed the solder on all contacts of the chip and tried the game one more time. Since there was no change at all, I removed the chip and tried to read it with my EPROM programmer. My programmer didn’t have a driver for this type (Toshiba TC538200 mask ROM), so I used the EPROM equivalent M27C800 instead.
The resulting file (checksum 4BEA7001, as above) had 100575 differences when compared against the expected data of 046-p2.sp2 (F182CB3E).
Fixing the issue
This was proof enough that the P ROM was indeed bad. I programmed the correct data to an M27C800 EPROM and soldered it into the PROG PCB.
A quick check with the Universe BIOS confirmed that the program ROMs were now fine:
And also the game itself showed no green tint or graphic glitches. I played it for a while and also let it run in attract mode for some hours, just in case. Here are some screen grabs of the fixed game:
