desertrout
Member
More of a general troubleshooting aside rather than anything Commodore specific, but: I recently acquired an early-model VIC-20 in its box with all the bits (manuals, transformer, composite cable, as well a datasette for good measure), but sold as powering on but having no video. Got it for cheap, thought it would be a easy restoration project as no video / black screen appears to be a common, fixable issue.
The machine arrived exactly as described. After some troubleshooting, including that the system was getting sufficient power in the right places, CPU was going into reset, activity on D/A lines, and of course that the video cable had continuity, I figured the Kernal ROM and/or VIC chip could be faulty (as per other sources).
To narrow it down, I borrowed a couple known-working, similar-model VIC's from a friend to swap chips. But when I plugged them in, they did exactly the same thing as mine - power on, no video.
What I didn't think to do was verify that the composite cable was the correct one for VIC's. Sure, it had continuity, but ON THE WRONG PINS. I rewired the cable and bingo-bango the machine works perfectly fine.
If I'd had another VIC-20 or C-64 video cable around (which I don't) I would have of course tested the machine with it and discovered the issue early on. But for some reason I decided that it was unlikely the cable that came with the machine was the incorrect one and moved on. I was on the verge of buying a Kernal ROM or Jiffy DOS, and it would have been for naught.
Lesson learned / reinforced!
The machine arrived exactly as described. After some troubleshooting, including that the system was getting sufficient power in the right places, CPU was going into reset, activity on D/A lines, and of course that the video cable had continuity, I figured the Kernal ROM and/or VIC chip could be faulty (as per other sources).
To narrow it down, I borrowed a couple known-working, similar-model VIC's from a friend to swap chips. But when I plugged them in, they did exactly the same thing as mine - power on, no video.
What I didn't think to do was verify that the composite cable was the correct one for VIC's. Sure, it had continuity, but ON THE WRONG PINS. I rewired the cable and bingo-bango the machine works perfectly fine.
If I'd had another VIC-20 or C-64 video cable around (which I don't) I would have of course tested the machine with it and discovered the issue early on. But for some reason I decided that it was unlikely the cable that came with the machine was the incorrect one and moved on. I was on the verge of buying a Kernal ROM or Jiffy DOS, and it would have been for naught.
Lesson learned / reinforced!