I thought it would be interesting to see if I could repair some Commodore computers. I picked up four VIC-20 and two C64 computers that were sold for parts or repair. I also picked up a working C64 and C64C. I will post my progress on this page. I'm not sure how this is going to go! :)
My First Repair... a VIC-20
The first computer I am working on is a VIC-20. When I first turned it on, the video output looked pretty bad. It wasn't even fully readable and it was flashing in and out. After a replacement capacitor (C57) and some tuning of the trimpots (R7, R32) for the video, everything (except the keyboard, lol) is looking pretty good. I will fix up the keyboard later. I also plan to thoroughly clean the system, as it's pretty dirty. I may also replace all of the electrolytic capacitors. I need to research other common failures in these systems and see what suggestions are out there for other recommended fixes, part replacements, and recommended maintenance.
Board Assembly: 324003
Board Label: R-7HB
Board S/N: D-094473
Case S/N: 716908
VIC-20 #2
A quick fuse replacement and adjustment of a trimpot, and VIC-20 #2 is looking great!
Board Assembly: 324003
Board Label: KU-14194HN
Board S/N: F65806
Case S/N: 298654
VIC-20 #3
Had a key stuck down. After disassembling the keyboard and cleaning contacts with isopropyl alcohol, the keyboard is working well. This, along with a quick trimpot adjustment, has the system working well.
Board Assembly: 324003
Board Label: W-18 94HB
Board S/N: F187671
Case S/N: 1691070
VIC-20 #4
This unit has a bad VIC-I chip. After reseating the ROMs and bringing in a VIC chip from another system, everything tests fine. Now, I need to track down a replacement VIC-I chip.
Board Assembly: 324003
Board Label: W-18 94HB
Board S/N: 496618
Case S/N: 729461
C64 #1
After some troubleshooting, I believe this system has a bad PLA. I have parts on order to build a bunch of Daniël Mantione's PLA20V8s. After I get a good PLA in place, I'll see what other issues I find.
Update: The system is up and running. It had a bad PLA and bad RAM. The kernal ROM is a bit flaky, so I will need to track down some ROMs. The keyboard needed some love, too.
C64 #2
Same issue as C64 #1 -- a bad PLA (to start).
Update: The system is up and running. It did have a bad PLA.
In addition to what's pictured above, I added heat sinks to the ROMs, processor, and SID.
C64 #3
Purchased as a working unit.
C64C
Purchased as working unit.
More to come...