Commodore 64 repair, machine #2

So the prior Commodore 64 audio issue had seemed to be resolved, but when I went to test it with an actual demo it didn’t seem to work. Frustrated I figured I should look into the 3rd C64 that was given to me by Matt C and Mike W. It came from the surplus of Grande Junction in VaBeach, but had markings on it like it had come from CHKD Thrift in it’s past.

Originally there was no life on powerup, but then that changed. It was spotty and upon poking around the glass fuse holder was to blame. Reflowed solder on it and it will still problematic, cleaned the fuse and holder and it was still spotty, bent holder to get tighter grip on fuse and that cured it.

Next sympton was pink screen, orange screen, but not working. Searching online I found a bunch of pointers to things I had already tried (voltage checks.) Finally pointers said it might be the PLA chip, so I desoldered the one out of the donor board (#2) that supplied the SID chip for #1, and placed it in the socket of #3. Came to life, and there was sound from the demo loaded from the SD2IEC.

The metal shielding in #3 was way rusted, and bottom plastic heavily stained. So I combined some parts from #2, and wirewheel cleaned the top shield (which acts as heatsink for ICs.) I sprayed it with yellow rustoleum paint and it looks like a sad Tonka truck but it will perform it’s function and hopefully not rust more.

So check mark on a C64 finally. Claude and Tom are printing me a case for the SD2IEC — whoot! Now to find more d64 images.

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