Bucky O’ Hare repair log #3

Received from Portugal this Bucky O’ Hare PCB for repair:

Board was failing the POST all the time showing a ‘SOUND SYSTEM BAD’ message

The sound system was previoulsy reworked : the YM2151 was socketed

and the ‘054986A’ audio module had electrolytic capacitors replaced with thru-hole ones:

The solder side of the module showed signs of repairs too :

I suspected a broken trace underneath the module so I replaced it with a good one taken from a parts board.The error on POST changed to this :

I looked at the board and found that actually the device @C4 is the custom ‘054539’ while the one @C5 is 32k x 8-bit SRAM (whose data/address bus is connected to the custom)

Probing the RAM revealed that data lines were all stuck high:

Piggybacking it had no effect so most likely the ‘054539’ ASIC was bad.I removed it:

Soldered back a spare :

Board booted up fine and entered in game with no further issues.Another repair accomplished.