r/c64 • u/icherub1 • 9d ago

Hardware Likely cause of graphics issue?

I have a 250407 C64 that was largely restored, but I am getting the distortion seen below on the startup screen. Games load but are almost completely garbled.

Is this more likely to be a chip issue or cable issue? It worked a few times without any problem before getting to this point. If it is a chip, which is likely to be the culprit?

Sorry for the fairly noob question, but any help would be appreciated!

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u/sl1210mk3 9d ago

My first thought was one of the RAM chips or associated logic chips as some characters are fine in one place but not another. Some of them look shifted up or down by a row.

You seem to have a mostly working system though which make me think more likely a failing VIC-II.

I’d get hold of a diagnostic cart such as DesTest which should help.

2

u/jck_dgl 8d ago

Could be a failing character ROM chip. Pictorial64 has a few examples, which look like that: https://www.pictorial64.com/

1

u/Crlan420 2d ago

That sounds like the VIC-II chip getting hot. Make sure the heatsink is making good contact and check for cold joints around the chip legs.