Commodore 64 Display problem.

[birdboy385]

Hey guys. I managed to come across this commodore 64 from someone. The image below shows that when powered on, it gives a strange display. I've never worked on vintage computers / game systems before so I'm not really sure where to even start with this other than completely dissecting it and checking for bad solder joints which I didn't see.

[birdboy385]

Re: Commodore 64 Display problem.

also all those black marks are the spots on my cruddy camera lens. Sorry I'm in need of a new phone lol.

[stj]

Re: Commodore 64 Display problem.

put the metal cover back over the graphics chip - it's the cooler.

then touch the 8 ram chips - 4164 or similar.
if you burn your finger it's bad.
one other thing - check the psu is actually giving 5v - the potted psu's had a habit of failing in a bad way.

[birdboy385]

Re: Commodore 64 Display problem.

ok I'll give that a try although I'll probably use a thermal gun to check the temperature rather than actually burning myself lol.

[stj]

Re: Commodore 64 Display problem.

no fun.

[birdboy385]

Re: Commodore 64 Display problem.

Lol well I plugged power into it and measured volarge at various legs on the board. I was getting 4.3 and 5.1 volts. Can't really get my multimeter leads in the power supply end given how narrow it is also without knowing which pins should be what. I've also found 8 Texas instrument chips labeled ap8410. I'm assuming those are the ram since there doesn't seem to be 8 other identical chips.

[birdboy385]

Re: Commodore 64 Display problem.

I also did touch all the chips lol, they all felt normal.

[stj]

Re: Commodore 64 Display problem.

8410 is probably the date, year+week

so 4.3 souldnt be there.
http://www.devili.iki.fi/Computers/C...ront_page.html

[birdboy385]

Re: Commodore 64 Display problem.

ahhh so if I'm reading this right, I should be getting 5v and 9v. never 4.3. So the problem more than likely is actually the power supply. I guess I'll try to rip open the supply and look for anything obvious while attempting not to kill myself.

[stj]

Re: Commodore 64 Display problem.

good luck.
the original psu's are potted with resin.
https://www.youtube.com/watch?v=oY6ycn7qmzo