Received a board from a friend – no sound. First think that popped into my mind was LM324 amplifier and I had not even looked at the schematics. That said – I had no way to test it..

Step 1 is to build up a bench adapter for my test rig. Takes a couple hours but once complete, I can switch PCB’s in seconds and I’m always certain the power, video and controls are 100%. I’d picked up a Crystal Castles PCB myself a while back and had been planning to build an adapter for it – so good timing.

Board #1 – In for repair

Reported no sound.

Replaced LM324@5B

Board works!

Board #2 – Board from my collection

After initial inspection and cleanup – the crystal was broken – replaced it.

Connected to power – no clock. Really?

There is nothing really going on here. Maybe I got a bad crystal – replaced it.. no clock. Then I tried a completely different speed crystal thinking maybe a got a bad lot.. still no clock. Turns out Q1 was bad. Clock restored!

From here it tests RAM, clears the screen – then watchdogs and starts over Woop Woop Woop.. It appears to be getting lost in the self test just before it paints the screen. The working board shows it walking through the video RAM (fast moving white dot) which takes a couple seconds. This board doesn’t spend any time at that testing step and watchdogs..

More to come – had to set it aside for other repair work…