Ahh, so nice to see a fellow SID remover and switch fixer :) I've seen too many repair videos where they leave the SID in the socket and in my opinion the first order of business when troubleshooting/fixing a C64 is to always remove the SID. I really like the format of your videos and they remind me of Noel's Retro Lab which is one of my favorite retro channels :) Excellent work..
Once upon a time, "U2 is bad" would had peed me off. These days I agree with you. I didn't realise the C128 style keys were "cost reduced", I thought they looked better than the regular C64c keys (which is what my one has)
Interesting video. I've never got this deep into a 64 repair, but I think the time may be coming. I've only done chip swaps and pulled out a schematic to wire in a reset button. My father (in his 80s) has a stack of 64s he's collected over the years. I suspect they might find their way to me in the next few years. I plan to restore and rehome as many as I can. They deserve a life outside of a closet. Also... I wonder if that weird button on that 64 with the weird ROM socket was some sort of old school kernel switcher. Nowadays I've seen people wire up an arduino, tapping into the keyboard to use a key combo to switch kernels without an ugly switch drilled into the case.
I've heard the 8521 is just a HMOS version of the 6526. But why would Commodore make a HMOS version only to go back to using NMOS? Were there other issues with this chip besides failing the interrupt test?
@@TheRetroChannel I know, that it is sometimes installed as U2 on Assy250466. I have the same model with the 8521. I also have a failed interrupt test and other than that no problems. I did not find any datasheet for it.
30:20 The 2 longer screws on a C64C are meant to go in the 2 bottom corners of the mainboard... sadly, I've seen other cases damaged by putting those where the shorter ones should be. Thanks for the video! -- JC
That may be the 8520 used in the Amiga, which I confused for this 8521. There's a recent post on Reddit where somebody has the same issue with the same board rev and 6526 + 8521. According to another user on Reddit the 8521 is just a HMOS version of the 6526, and Commodore went back to using the 6526 numbering with later HMOS versions to avoid confusion
Had exactly the same issue this week, so am happy to see this here. I was also suspecting the diag test somehow did not like the 8521. Seems to be more and more confirmed
@@TheRetroChannel hehehehe Okay fine. But when I die and you find an RF shield reinstalled on my C64, you'll know why. We have enough RF pollution as it is, and I wouldn't want to make it worse. Signed... an amateur radio operator
Ahh, so nice to see a fellow SID remover and switch fixer :)
I've seen too many repair videos where they leave the SID in the socket and in my opinion the first order of business when troubleshooting/fixing a C64 is to always remove the SID.
I really like the format of your videos and they remind me of Noel's Retro Lab which is one of my favorite retro channels :) Excellent work..
Removing the SID is a killer repair tip.
Once upon a time, "U2 is bad" would had peed me off. These days I agree with you.
I didn't realise the C128 style keys were "cost reduced", I thought they looked better than the regular C64c keys (which is what my one has)
Very nice repair and very well explained! Good job!
Managed to find replacement switches, the OG plastic rocker needs to be kept.
Interesting video. I've never got this deep into a 64 repair, but I think the time may be coming. I've only done chip swaps and pulled out a schematic to wire in a reset button.
My father (in his 80s) has a stack of 64s he's collected over the years. I suspect they might find their way to me in the next few years. I plan to restore and rehome as many as I can. They deserve a life outside of a closet.
Also... I wonder if that weird button on that 64 with the weird ROM socket was some sort of old school kernel switcher. Nowadays I've seen people wire up an arduino, tapping into the keyboard to use a key combo to switch kernels without an ugly switch drilled into the case.
Nice work and troubleshooting. Long live the commodores:)
The 8521 always lead to a bad U2 after the interrupt test with the diagnostic software.
I've heard the 8521 is just a HMOS version of the 6526. But why would Commodore make a HMOS version only to go back to using NMOS? Were there other issues with this chip besides failing the interrupt test?
@@TheRetroChannel I know, that it is sometimes installed as U2 on Assy250466. I have the same model with the 8521. I also have a failed interrupt test and other than that no problems. I did not find any datasheet for it.
30:20 The 2 longer screws on a C64C are meant to go in the 2 bottom corners of the mainboard... sadly, I've seen other cases damaged by putting those where the shorter ones should be. Thanks for the video! -- JC
Yes you're right. I do recall a couple of longer screws in previous 64C's, just didn't think of it this time. Thanks!
Well done on the repair work! Every c64 is worth saving... even those with a few missing "teeth" (keys!) 😁👍
Really well done!
My understanding of the 8521 CIA is that it doesn't generate TOD the same way the 6526 does, so this may explain why diag marks it bad.
That may be the 8520 used in the Amiga, which I confused for this 8521. There's a recent post on Reddit where somebody has the same issue with the same board rev and 6526 + 8521. According to another user on Reddit the 8521 is just a HMOS version of the 6526, and Commodore went back to using the 6526 numbering with later HMOS versions to avoid confusion
@TheRetroChannel ah, you're right. I was confusing it with the Amiga CIA too. It's good to know it's not really a fault.
Had exactly the same issue this week, so am happy to see this here. I was also suspecting the diag test somehow did not like the 8521. Seems to be more and more confirmed
lol I just realised my C64C still has the plastic on the badge
The big question, do you peel it off or leave it be
@@TheRetroChannel Leave it it still undamaged and protecting the badge under it :)
U2 is bad, Simple Minds better :o)
Don't be an RF polluter. Put your RF shields back on.
Never!
@@TheRetroChannel hehehehe
Okay fine. But when I die and you find an RF shield reinstalled on my C64, you'll know why. We have enough RF pollution as it is, and I wouldn't want to make it worse.
Signed... an amateur radio operator