I just got this happening to my vic-20....it started tonight while i was playing a game..
hum in audio and wavy picture and the red/power light on the vic is on. I just lost pic and nothing comes on anymore and i have switched power adapters and games and still get a humming sound and no picture...
I suspect the voltage regulator has failed. If the VIC is not turned off immediately you see and hear the hum, it will be damaged, which I suspect has happened in your case.
Thanks for all your help...
I figured it out....It was the powersupply..i had 2 bad ones and once they got hot they would fail...switched out for the 3rd powersupply and everything worked fine.