[vcf-midatlantic] Museum Report 2018-11-16

[Ethan Dicks]

On Wed, Dec 19, 2018 at 11:57 AM Michael Pohl via vcf-midatlantic
<vcf-midatlantic at 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