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Commodore VIC-20 (mostly) dead!!! :(

E

Eep386

Experienced Member
Joined
Jul 15, 2010
Messages
275
Location
Woodland, CA
Hello,

I purchased a VIC-20 off eBay a week or so ago (buyer said it "powered on sold as-is" :sarcasm:). When I plugged it in and powered it up, the thing does indeed turn on, but it produces a mostly black/blank, rolling picture. (Blech, I knew it was too good to be true...)

Opening it up reveals it's an early model VIC-20 (the two-pin power supply version). Perchance the power brick or the power regulators on the motherboard are bad? Or could it be something else?

Oh yeah, I almost forgot to mention, a datasette when hooked up to the VIC-20 does nothing. Motor doesn't turn even when FF or REW are pressed...

Thanks,

Aaron
 
Well, you've come to the right place. We all love our vintage machines and the VIC-20 certainly qualifies as a nifty vintage computer. You probably got a real good price on your auction buy, but now you find it simply doesn't work. It 'powers on'. Where have I heard that expression a million and one times, except eBay. I feel compelled to give you my advice. Don't buy vintage computers that state only that 'powers on'. Sure maybe you got a good price by 'taking a chance' but after you factor in the shipping costs you paid, it just wasn't worth the headache, and now you have a doorstop. VIC-20's go pretty cheap on eBay to begin with anyway, because there were a bazillion of them made. Well made, I might add too, since so many are still running fine after almost 30 years! You could have thrown in a little more money and got a known working one. Watch for auctions showing a screenshot of the unit actually in use, and you're pretty sure of getting a working unit delivered.
As for the unit you have - chalk it up to experience and simply go find a 'good' auction - with a screenshot! Save the one you have for parts. I really am trying to help you. Don't throw more money after bad trying to figure out what parts to replace. Murphy's Law says that if you replace the power supply, it'll be the CPU, or if you replace the CPU, it'll be the motherboard. Unless you really wish to 'get into' Commodore repair work and learn a new craft - just start over and find another VIC-20.

Giving your post a little more thought - I'm assuming you do have the VIC-20 properly hooked up, right? If you didn't get a user manual with your VIC, you can Google one to make sure you've hooked everything up properly.
The cassette buttons should work when the VIC-20 is 'powered on', so it looks like you have a problem.
 
http://personalpages.tds.net/~rcarlsen/cbm/vic20.txt

http://www.zimmers.net/anonftp/pub/cbm/vic20/index.html

You'll need at least a voltmeter and a logic probe. An oscilloscope helps a lot. A logic analyzer is a plus. Start with the transformer (the original was under-spec) and work your way from there. Power supplies, clocks, logic.

Don't forget checking to see that socketed chips are seated and connector traces aren't cracked (the obvious mechanical stuff) before digging in too deep, though.
 
Vint said:
It 'powers on'. Where have I heard that expression a million and one times, except eBay. I feel compelled to give you my advice. Don't buy vintage computers that state only that 'powers on'.
Click to expand...

Yep. I got caught with that one in my early days of collecting and with a Vic 20 also, no less. I did manage to fix mine in the end with the help of some of those documents mentioned in the previous post.

Stick with it and be patient. These things are fixable.

Tez
 
saundby said:
You'll need at least a voltmeter and a logic probe. An oscilloscope helps a lot. A logic analyzer is a plus. Start with the transformer (the original was under-spec) and work your way from there. Power supplies, clocks, logic.
Don't forget checking to see that socketed chips are seated and connector traces aren't cracked (the obvious mechanical stuff) before digging in too deep, though.
Click to expand...
You're talking to someone who's too broke to afford such fancy toys as an o-scope - all I have is an el-cheapo multimeter to see me through. I did do a quick visual inspection of the board, which revealed a nice leaky/rusting 4700uf capacitor. I replaced it (thank you radioshack!), retested, still no go. It did however change the dead screen patterns a bit (instead of a vertically skipping line with what looks like a stretched "o" in the middle, it now skips both vertically AND horizontally! :D)

Investigating the socketed chips, everything looks like it's in there nice and tight. I'll be consulting the vic20 repair guide for this - I do happen to have a stockpile of old 386/486 IDE paddle cards which have 74LS245 chips among other goodies, so with some careful desoldering I might be able to get this fixed, hopefully without throwing a lot more money at it.
 
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One more thing, anyone got a working VIC-20 power pack they don't need anymore? I'd like to see if it's the powerpack at this point...
 
Eep,

This may be a stretch since I'm probably volunteering you and someone else :) but where are you located? Possibly someone close by could bring some spare parts and help figure out what's wrong. Probably nothing new but here's a quick troubleshooting chart for the vic-20 on Bo's site Worst case scenario maybe someone here does have a spare they could loan or sell, or even some cheapo store (or check craigslist too).

- John
 
barythrin said:
Eep,
This may be a stretch since I'm probably volunteering you and someone else :) but where are you located? Possibly someone close by could bring some spare parts and help figure out what's wrong. Probably nothing new but here's a quick troubleshooting chart for the vic-20 on Bo's site Worst case scenario maybe someone here does have a spare they could loan or sell, or even some cheapo store (or check craigslist too).
- John
Click to expand...
Hey, thanks for the reply. I live in Graham, Washington, which is close to Spanaway and a drivable distance from Tacoma and Lakewood.

Also I forgot to thank everyone for providing helpful replies. I hope to get this beast running soon...
 
Well, I built my first 5 computers with a digital VOM (nixie tubes), a bug light, and a home made logic probe (schematic courtesy 101 Electronic Projects, a magazine supplement from the '70s.) So an o-scope isn't necessary. I got my first scope at a "garage sale" from a local electronics manufacturer. It was a tek 910 with an NFG trigger circuit. I fixed it in an evening, and had a scope of my own.

The old Vic takes 9VAC, so a transformer can be used (insulate your connections.) I made one of my own after blowing my first Vic P/S by throwing a 110VAC=>9VAC transformer into a project box and splicing on a standard line cord and a cord literally taken from a toaster on the Vic side, shaved to fit with a pocket knife.
 
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