Was that a typo regarding CPU socket connection pin 16 or pin 15?

Hi dpalmeira, You are doing good work in methodically checking everything on the board. Slowly and steadily you will beat this to your will. Remember that when you get frustrated take a break and do something else. Am I correct in understanding that the CPU socket had a faulty wiper connection? Is t...

Here, Adrian talks about experiences with chip testers and diagnostic cartridges

Hi dpalmeira, I just want to touch on a subject that I discussed earlier in this thread regarding fake chips and also too chips that go out of specifications due to age, failure, etc.... I found this great YouTube video from Noel's Retro Lab on fake chips. Very interesting! He goes into detail on co...

Hi cmherndon79,


I was just browsing YouTube and found this very interesting video from Noel's Retro Lab.



Have you investigated the clock circuit on your C64 mainboard?

I found some more IC chip tests.

Ignor the stuff I've written in Biro on the last image. I was checking out something on a C64 mainboard.

I think it's U8. Run the oscilloscope on all of the pins observing the various signals including ground and power. Also pull out all the 3 ROM chips, Basic, kermal and CHAR. They have a Read write line attached to the CPU chip. Try using the PLA chip from your known good working condition C64. We ne...

Hi dpalmeira, Do you have any observations on pin 15 (S/LUM) of VIC II chip as you are running the chip swaps? Sometimes the dead test cartridge can take some time to initialise itself. Maybe keep it in and on for a minute to be sure while conducting observations. Keep the oscilloscope observations ...

Maybe start with all the socketed chips out, even both CIA chips (U1 & U2). Only leaving in the CPU chip, VIC II chip and the PLA. Then slowly add one chip at a time until the Logic signal from Pin 38 of the CPU goes funny. Check for the other logic signals on the other CPU pins too every time a...

Hi dpalmeira, Only too happy to help. I will admit that I'm not the greatest at this stuff, apologies. That's fantastic progress and very interesting. Well done! :D You have presented a great deal of useful observational information on what you have just done. It will take me some time to fully dige...