"New" VIC, video issue

SkepticalPete · Post by **SkepticalPete** » Thu Sep 09, 2010 6:08 pm

Hi, been lurking here for a while but haven't posted yet. Finally got around to acquiring a VIC--though it was my first ever computer, my parents made me sell it if I wanted to upgrade.

I found a later-edition VIC in what appears to be exceptional condition, and it powers up properly and behaves just fine for a while. But after a couple of minutes, the background colour goes black; everything else seems to remain just fine, including the cyan screen border. BASIC programs continue to run normally, and Run/Stop-Restore returns the colour to normal, at least for a while. Occasionally I've noticed a bit of a "zipper" pattern down the left half of the first column of text when this has happened.

It strikes me as maybe an overheating issue, but I haven't seen any reference to this specific problem so thought I'd ask before messing around with it.

I've already tentatively ruled out the power supply, as the same problem occurs with my late-vintage C64C supply.

Any ideas? I really hope I didn't get a complete dud of a machine...

Thanks!

6502dude · Post by **6502dude** » Thu Sep 09, 2010 6:49 pm

If you have another Vic-20, try swapping 6560 chip.

SkepticalPete · Post by **SkepticalPete** » Thu Sep 09, 2010 6:52 pm

If you have another Vic-20, try swapping 6560 chip.

Alas, this is my only VIC so far...

Just tried reseating the socketed chips, no effect. Sigh.

SkepticalPete · Post by **SkepticalPete** » Fri Sep 10, 2010 6:55 am

On the bright side, found another VIC that should arrive in a couple of days. It has been tested more thoroughly than the last; hopefully won't have any of these sneaky issues. Between the two I should be able to get a single complete system that looks almost like new!

SkepticalPete · Post by **SkepticalPete** » Mon Sep 13, 2010 2:54 pm

Well, second VIC arrived today and it seems to be working perfectly. It's an older model (2-prong power supply) but also in quite decent shape considering its age and thus far no issues.

Now just have to wait until it's my turn for a Mega-Cart to "test" the cartridge port!

Maybe at some point I'll try swapping the VIC chip into the newer machine, but I don't see much point messing around with that when the older one is working perfectly.