Power supplies cause trouble all the time in the car panel. They use a voltage doubler circuit to get the 30 Volts and the caps go bad all tthe time, Then you get ripple and it will ruin the ram chip on the board. Ram chip is in a socket as processor is.If it's real old, the EPROM is bult into the processor an intel 8749 chip. If it's an 8749 chip the checksum should be EFC1.