cuda@ihuxv.UUCP (mike nelson) (02/10/84)
I recently found a solution to the *Sparkle* problem of the C64.
I managed to find a technician at a commador service center that was
willing to tell me what the fix was. Apparently there are levels of
severity and so two fixes (that I know of). The first is to place a
500pF cap from the AEC pin of the VIC chip to ground. The AEC lead
is accessable from a test pad just to the left of the outside of the
RF shield of the VIC and clock circuits. Then the ground side was
just next to C34, an electrolytic cap right next to the SID chip.
It seems there should be an easier place to put the cap but
that's where he told me to put it. I started with a 470pF cap and
found that it cured most of the sparkle. I added another 150pF cap
in parallel (physically, not electricly) and improved the performance
even more. I added another 47pF cap (total 667pF) and the problem
is almost gone. Now I only occasionally see a one or two bit error
instead of the whole charicture being constantly garbled.
The other fix is to replace the charicture generator rom. A
$22 expence just for the chip. I've also heard of these being
combined.
I hope this helps someone else. I managed to fix mine with a
soldering iron and some parts rather than pay XX.XX bucks. Happy
soldering.
Mike Nelson
AT&T BL
Naperville Il.
ihuxv!cuda