On Wed, Dec 19, 2018 at 11:57 AM Michael Pohl via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
I signed up to bring our non-working Commodore 64 to the workshop on 12 JAN. The power light comes on, but there is no video from either the RF modulator or the 8 pin video jack. We ran some basic daignotics - power supply produces the correct voltages, voltage is present at specific places on the motherboard, fuse is good - but now we are stuck.
"Black screen" Commodore 64 is commonly the PLA chip. It's a programmed 82S100 PLA that implements the memory map. Replacements are available. You can borrow one from another machine and see if that's the problem. There is a smaller chance it's a bad DRAM chip. Those occasionally fail. -ethan