Commodore VIC-20

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Commodore VIC-20

Postby lesliev on Thu Jan 03, 2019 9:12 am

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.
lesliev
 
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Re: Commodore VIC-20

Postby lesliev on Thu Jan 03, 2019 6:56 pm

Here's a pic!
Attachments
vic20.png
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Re: Commodore VIC-20

Postby acsi on Thu Jan 03, 2019 7:12 pm

Hi,

I would be interested in taking this off your hands and repairing it.

Where about in the country are you?
'acsi' on trademe
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Re: Commodore VIC-20

Postby lesliev on Thu Jan 03, 2019 7:20 pm

I'm in Auckland, North Shore.
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Re: Commodore VIC-20

Postby acsi on Thu Jan 03, 2019 7:30 pm

Would you be ok to post or courier it? (At my expense of course :D )
'acsi' on trademe
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Re: Commodore VIC-20

Postby lesliev on Thu Jan 03, 2019 10:45 pm

acsi wrote:Would you be ok to post or courier it? (At my expense of course :D )

Yes, I'll PM you to make arrangements.
lesliev
 
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Re: Commodore VIC-20

Postby floppylobster on Fri Jan 04, 2019 8:58 am

lesliev wrote:Since it had occasionally been taking a bit longer to power on


Have you tried a different power supply?

I'm on the shore if you want to borrow mine to test it.
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Re: Commodore VIC-20

Postby lesliev on Sat Jan 05, 2019 6:43 pm

floppylobster wrote:
lesliev wrote:Since it had occasionally been taking a bit longer to power on


Have you tried a different power supply?

I'm on the shore if you want to borrow mine to test it.


No, but it's a simple AC transformer and I tested the output, which seemed correct. Thanks for the offer!
lesliev
 
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Location: Auckland

Re: Commodore VIC-20

Postby acsi on Tue Mar 12, 2019 3:31 pm

Finally had the chance to look at this properly.

Simple fix in the end as the Vic chip is faulty. Now to source a replacement as the only spare I have turns out to also be faulty :(
'acsi' on trademe
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Re: Commodore VIC-20

Postby lesliev on Fri Apr 26, 2019 11:46 am

Oh wow, glad you figured it out! VIC chips are a bit rare now though.
lesliev
 
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Re: Commodore VIC-20

Postby acsi on Fri Apr 26, 2019 7:40 pm

Yeah. Luckily I have a spare which also has a socketed Vic chip so I was able to test.

Interestingly both are the ones with 2 prong power connections but both are different. Can't plug the power supply into the other.

Unfortunately it also blew the 3.15A fuse on the motherboard the other day :cry: got some 3A slow blow ones to replace it.

I wound up giving the original owner $100 for the Vic and gear plus the $65 for the replacement Vic chip (rare is expensive although I could have risked Alibaba for a lot less).

The Vic has a Pet style keyboard and came with a black C2N like this one https://www.worthpoint.com/worthopedia/commodore-pet-cbm-2001-data-cassette-1818383154

Anyway hopefully the Vic isn't faulty in some other way
'acsi' on trademe
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