Dead VIC chip?

maguman · Post by **maguman** » Fri Feb 19, 2010 10:29 pm

Hi

I have just tried to use an older style VIC-20 after a few years of relative inaction. When first plugged in, I got a standard screen border but no text. Next, this reverted to a partial screen checkerboard of random characters and some random noise. Now no picture at all - just a back screen.

My immediate reaction, since both screen and (initially) sound went wrong was the VIC. Has anyone seen something similar and/or do you have any better ideas of the problem? Appreciate any help I can get.

I plan to hunt around for another 6561 anyway...

Vic20-Ian · Post by **Vic20-Ian** » Sat Feb 20, 2010 12:48 am

Doesn't sound good. Sounds like character rom first then maybe the Vic to me.

I would get the PSU checked out before plugging it into another Vic20.

maguman · Post by **maguman** » Sat Feb 20, 2010 1:07 am

Vic20-Ian wrote:Doesn't sound good. Sounds like character rom first then maybe the Vic to me.

I would get the PSU checked out before plugging it into another Vic20.

I thought about the PSU. It is the older two prong type. These are meant to be 9V AC. I checked the one I have and it is reading a solid 10.6V AC on a multimeter. I thought less than 12V AC would be fine. Is this likely to be the cause?

Barney · Post by **Barney** » Sat Feb 20, 2010 2:03 am

Same thing happened to me. I thought it was the Character rom but that wasn't it. Sombody else on Denial diagnosed it as a possible RAM problem. One of the ram chips is likely bad and needs to be replaced. Good luck.

Barney

maguman · Post by **maguman** » Sat Feb 20, 2010 2:42 am

Barney wrote:Same thing happened to me. I thought it was the Character rom but that wasn't it. Sombody else on Denial diagnosed it as a possible RAM problem. One of the ram chips is likely bad and needs to be replaced. Good luck.

Barney

I think I secretly hoped it wasn't a RAM problem but a socketed chip. Finding a known working PAL VIC will probably take a while to eliminate that potential problem.

Vic20-Ian · Post by **Vic20-Ian** » Sat Feb 20, 2010 5:00 am

Power it up a few minutes and touch the ram chips, the failed one may be hotter than the others - from a previous diagnosis this worked for me.

You might find ram chips on ebay.

maguman · Post by **maguman** » Fri Mar 05, 2010 9:19 pm

After pulling it apart, and picking up a second VIC, I managed to find a dead BASIC ROM. Switched it out - came up pretty quickly.

Seemed a bit odd (to me) for a dead BASIC ROM to produce this set of effects, but that was the cause.

Thanks for all the help.

Barney · Post by **Barney** » Sun Mar 07, 2010 5:21 am

Now you got me a little excited maguman. Maybe my Vic doesn't have a ram problem. Maybe it's a ROM issue. Anybody out there have any spare ROMS? If you do, how much? Thanks.

Barney

maguman · Post by **maguman** » Sun Mar 07, 2010 5:32 am

There seem to be some places on line that have them, such as the following:

http://www.arcadecomponents.com/customroms.html

I thought $4.99 was pretty reasonable.

The real tell-tale was how hot the ROM became - very hot after 5 minutes. That wasn't enough, though. It was actually hotter than the VIC chip (a pretty big effort for a ROM). Funnily enough, I had checked the temp on all the other chips (besides the ROMs) previously, so I never spotted it.