Denial

Sorry for the delayed update. In order to verify the issue I soldered the port back on and the issue returned. While the connector was off, I did test it thoroughly and I can't detect any particular issue with it. I don't have a spare connecter to put on the board, but I have a replacement on order ...

Update: This has been a tricky one. I finally gave it and decided to remove the cartridge port to see if there was something about it in my testing that I missed. I also tried injecting some power on the RAM3 line with all the logic ICs in that area removed to see if I could find a short that way. I...

Update: started looking at it from a power filtering hypothesis which lead me to check all decoupling caps and ferrite beads to see if any filtering was shorting on one of those components. I replaced all the decoupling caps. The board looks nicer 😅. But it did not fix the issue. I thought maybe it ...

I'm happy my suggestion have helped, though I'm not an expert about the VIC20 repair in particular. I've not seen often a ceramics to fail short, yet (it is common on tantalums, but then you have other symptoms). Noise on power supply rails is a typical sign of a failing electrolytic capacitor. I w...

Interesting repair! I have a stupid question: have you checked that the noise on the power supply rails is not too large? No stupid questions here, thanks for asking. I knew there was a good chance after the weeks I've spent on this I would miss mentioning many things I've tried. But yes I have che...

Hey everyone, Long time reader, first time poster. I've been hitting my head on the wall with the repair of a VIC20 for a few weeks now. I'm fairly experienced with these things but this one is befuddling me a bit. It initially presented with a black screen. Replaced the CPU and it kicked into BASIC...