VIC-20 faint BASIC screen - bad power supply?

[TH2002]

Picked up a VIC-20 yesterday from a local thrift store, untested since it didn't come with a video cable in the box.

Got it home and noticed two things right off the bat:

• Tested it with the video cable I use with my C64, since it's the same type of connector and I assume it's the same pinout? Correct me if I'm wrong on this. Anyways, the BASIC screen is very, very faint and the colors are washed out - however, the obligatory "20 GOTO 10" scrolling program test seemed to work fine, from what I can tell.
• The power supply emits a noticeable humming sound, and sometimes the computer fails to start up at all.

Is it safe to assume my power supply is what's at fault here? Unfortunately using my C64 power supply isn't an option since this happens to be an older model VIC-20 with the two-pin power connector. Also, are original VIC-20 power supplies known to have the potential to nuke the computer when they start to fail, as can happen with C64 power supplies?

Thanks.

 

[Timo W.]

Also, are original VIC-20 power supplies known to have the potential to nuke the computer when they start to fail, as can happen with C64 power supplies?

Not really, since on the older VIC-20, the voltage regulation is completely done inside the computer. The PSU only supplies 11.5 V AC. It's just a simple transformer (hence the humming sound), so not much that can go wrong. The PSU is most likely not the issue.

 

[rittwage]

The video output is funny on the VIC, it's not exactly the same as the C64. There is a "high" and "low" video output, and there is also power on one of the lines (to power an external RF box) so be careful. Also, typically the video level adjustment needs to be tweaked inside to look good with modern displays.

 

[TH2002]

Yep, I'm an idiot. Opened it up, adjusted the video level potentiometer and it looks perfectly fine on my TV now. Glad whoever owned this VIC-20 previously took very good care of it, since the inside is in fantastic shape.