Commodore Vic-20 with a Blank screen?

[CuriousRuru]

Hiya folks. I'm new to the forums and with Commodore's in general so bare with me. When i was 14 i purchased a lot of retro consoles and games while working with my father with his carpentry. in the lot was a Commodore Vic-20. Now back then when i tested it. the screen was blank as it is now. i figured it had to do with the video box because they're kind of crappy admittedly. now that i'm a little older and learned to solder and stuff. i dug it back out and hand-wired a 5-pin to composite cable so i could display it on my regular television monitor, After hooking everything up the Vic-20 turns on. but i'm left with a blank screen. However the monitor does flash/flicker as the vic-20 is powered on. I inserted a 'Serpentine' Game Cart into the socket and turned it on. Alas i can hear the Serpentine music. but i cannot see any video... I'm wondering what i might do to fix the issue? I've read that it could be the 6560-101 Vic chip. but i can't find any replacements or substitutes. and i really don't want to pay $300+ just to buy another one and that doesn't work either... Any guidance would be severely and graciously appreciated.

[beamrider]

Since you can hear sound with the cartridge, switch it on and type:

poke 36876, 220 : poke 36878,15

<Press return>

If you can here a sound then the KERNEL ROM and BASIC are working otherwise they are good candidates to swap.

But most likely it's the Vic chip since you get no display running the game so that would be the next candidate to swap, but as you say, you might as well just buy another Vic-20 as try to obtain one of those used.

[CuriousRuru]

Hey beam, Thanks for the reply though i don't seem to hear anything coming from the monitor at all whenever the vic-20 is booted up without a cartridge. i tried typing in that command you sent and nothing happened. at least i didn't hear anything personally.

[beamrider]

Okay - sounds like it may be the Vic chip and the BASIC ROM in that case, but honestly, it could be a lot of things. You really need a known working machine into which you can try the suspect ICs.

[CuriousRuru]

Awwww.. yeah i suppose that makes sense. That's a little depressing to hear, Vic-20's are way too expensive down where i'm at so. Thank you for the insight at least. perhaps i'll still browse the forums in the meantime.