I have a VIC-20 that I got from a friend, along with its assorted original bits: power supply, tape drive, expander cartridge and manuals. It worked great plugged into my LCD tv through the RF modulator - but only for two days, then the video signal disappeared.
First thing I tried was to buy a video cable to bypass the RF modulator, in case that had died. But it made no difference.
I thought I'd try my hand at fixing it. Since it had occasionally been taking a bit longer to power on, I suspected one of the capacitors might have slowly died - though they all looked good. I ordered replacements and replaced all the electrolytic capacitors on the board. I also cleaned it with alcohol and replaced the thermal paste on the power-supply components in the computer (it's the older model with the 19V AC power that gets converted to DC inside the computer).
But after doing this, there was still no video. I'd assume one of the chips might be dead, perhaps the CPU or the VIC chip. When powered on for a while, the CPU warms up a bit and the VIC chips warms up quite a lot, as would be expected from normal operation.
So at this point, I think a fix is beyond me. I'll need a second, working VIC-20 to start transplanting chips to see which might be dead, and I'm not a master at desoldering.
Does anyone out there want it for parts? Or the challenge of fixing it? The great thing about these early computers is that fixing them is actually possible.