Aug 032011

Brought 5 broken C64’s back from the RCM to try and ressurect.
This one just booted to a black screen.

On my initial checks I found that the 6510 CPU did not have a clock. The clock for this is outputted from pin 17 on the VIC chip. Although this was getting a clock input, it was dead on the output and was getting very hot. I replaced this with a known good one and fired it up again. Still got a black screen but clocks were now present.

A black screen is commonly associated with a dodgy PLA. I removed the PLA and replaced it with a known good one and the C64 now loaded up.
Next problem, there was no cursor and the keyboard would not type anything. These are handled by IC U1 which is a CIA. Again, I removed this chip and fitted a known good one.

The Commodore now fires up and works fine.
One down, 4 more to go (and a VIC20 but dont have a PSU for it)