Wednesday, 23 January 2019

Sunset Riders pcb repair

I got this pcb in a trade, it was described as not working. When It arrived it was confirmed not working, it just displayed a white flashing screen over and over again as it was constantly resetting (watch dogging). First thing I checked was the roms, they were in the wrong sockets but otherwise fine. Putting them in the correct sockets made no difference.

I then probed the main 68000 cpu and noticed a lot of stuck and floating address lines. I desoldered the 68000 (fun), this is the first time I've ever seen a 68k cpu go bad. Sunset Riders uses a 16mhz 68000 which I didn't have (the ones I have are only rated 8- 10 mhz) so I borrowed one from another konami board for now.

This got the board booting but it failed to get past self test, it complained about the eeprom and 2F / 3F. Powering off, holding down the test switch and powering on again fixed the eeprom issue but not 2F / 3F.



2F is the sound eprom which was corrupt but burning a new one with the correct data from mame made no difference. 3F is the 6116 ram for the sound section. I desoldered the ram but it tested fine, I started probing around the sound section and again found more stuck address lines on the cpu (Z80).

I replaced the Z80 and the board now passed self test everything looked good but the sound was just a constant noise with odd samples playing randomly. Interestingly the maskrom test wouldn't complete either, it just crashed after a few seconds. The only thing that made any sense to be causing this fault was the konami 053260 custom.


I removed the 053260 chip and then took a working donor from a Golfing Greats pcb, this fixed the sound completely.


Repair complete.

No comments:

Post a Comment