Have you tried Birt's case repair kits? (Hey Birt/Soigeneris) just 3D printed "bits" but they cover all of the common problems like case clips (all case variants), and screw posts
So, here are my thoughts on machine #4: First, when you did the final test after returning the CPU to the board, you didn't appear to have the dead test cartridge installed. Without that and without the CIAs or ROMs, black screen was no surprise. The next thing I'd suggest checking is if your GAL PLA is working. I've had more than one of those where one of the GALs programs fine, but then craps out when installed in a C64. This can happen immediately or only after the GAL PLA has been sitting around unused for a while. Just as a sanity check, pop it into your working 64 to make sure it's still good. If that's not it, I'd try swapping out the VIC-II. I've run into one machine where the clock was good and I was getting a black screen with the white line, which makes you think the VIC-II is working, just like you are, but the addressing was being screwed up by the VIC-II and since you did see some questionable signals on at least one of the multiplexers, I'd say that's a possibility. Again, just as a sanity check, I'd go ahead and test the 7805 and 7812 regulator outputs, just to be safe.
It looked like at the very end you tried the board without the test cart, but with no ROMs or CIAs. No wonder about the black screen. But of course that thing has probably more issues anyway, and it wouldn't have made a difference... (Or maybe the cart was inserted off camera?) Not like I haven't made this very mistake a few times already, hence why I noticed it. :)
Always wondered about rubbers - do we call them rubbers because you rub the paper (or, in this case, edge connector fingers) with them, or because they're purportedly made out of rubber? 🤔
as soon as you said all the main chips are socketed. my brain said: it'll be the memory then
Have you tried Birt's case repair kits? (Hey Birt/Soigeneris) just 3D printed "bits" but they cover all of the common problems like case clips (all case variants), and screw posts
Wow! Your repairs are so fast I had to watch your video twice!! :) Thanks for sharing
So, here are my thoughts on machine #4: First, when you did the final test after returning the CPU to the board, you didn't appear to have the dead test cartridge installed. Without that and without the CIAs or ROMs, black screen was no surprise. The next thing I'd suggest checking is if your GAL PLA is working. I've had more than one of those where one of the GALs programs fine, but then craps out when installed in a C64. This can happen immediately or only after the GAL PLA has been sitting around unused for a while. Just as a sanity check, pop it into your working 64 to make sure it's still good. If that's not it, I'd try swapping out the VIC-II. I've run into one machine where the clock was good and I was getting a black screen with the white line, which makes you think the VIC-II is working, just like you are, but the addressing was being screwed up by the VIC-II and since you did see some questionable signals on at least one of the multiplexers, I'd say that's a possibility. Again, just as a sanity check, I'd go ahead and test the 7805 and 7812 regulator outputs, just to be safe.
I suspect the VIC Chip
It looked like at the very end you tried the board without the test cart, but with no ROMs or CIAs. No wonder about the black screen. But of course that thing has probably more issues anyway, and it wouldn't have made a difference... (Or maybe the cart was inserted off camera?) Not like I haven't made this very mistake a few times already, hence why I noticed it. :)
Always wondered about rubbers - do we call them rubbers because you rub the paper (or, in this case, edge connector fingers) with them, or because they're purportedly made out of rubber? 🤔
It's odd that in the US, it means something soooooo very different....
More of a sepectrum guy here but could it be a bad Vic????
I concur