Dead VIC-20

Discussions for CBM PET, VIC-20, SX64, C16/+4 and Commodore 128 systems
banman
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Re: Dead VIC-20

Post by banman »

Hi eslapion,


That's a good point regarding Vic 20 computers using VIA chips.


rmzalbar
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Re: Dead VIC-20

Post by rmzalbar »

That's something I really like about the VIC-20. There's only the one IC that is custom, the VIC.
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banman
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Re: Dead VIC-20

Post by banman »

Hi rmzalbar,

Absolutely!

I understand that the Vic 20 computers were not as popular as the C64.

From what I understand, they however played an important role in the history of early home computing.
These were the first computer of any description to sell one million units. I'm also certain that these machines held a special place for people who had one back in the day.

I have 2 US manufactured cost reduced NTSC machines that were basically barn finds that I purchased. I'm unsure of how they made their way to Oz. Not in great shape by any means.
Both having all the socketed chips missing, no top casing or keyboards.

The machines started up no worries after replacing all the missing chips with known working ones.

That certainly says something about American manufacting standards and design.
rmzalbar
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Re: Dead VIC-20

Post by rmzalbar »

Yes, all my 8-bitters from the late 70s/early 80s look and work great. The 2-pin VIC-20 I have has a very pristine and pretty motherboard, with the sad exception of a burned "repair" some previous owner did after apparently misdiagnosing a dead zener diode. My Atari XL boards were made to a good standard as well. In fact I've never seen a bad board from that era, but that could be because I live in the U.S.A - I think in general our weather is just kinder to this stuff. I have a ZX81 that seems pretty solid, other than having suffered a dead ROM once, and of course a delicate keyboard ribbon (but still good.)
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Thingumybob
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Re: Dead VIC-20

Post by Thingumybob »

I feel bad. I never ended this thread. I know I fixed it because I don't have any units that don't work.

I'm going from memory now.

The screen I got with the horizontal lines was because there was a dry capacitor which was keeping the video signal too low. I believe it was the one just to the left of the rf shield. This is on an older 9VAC input style VIC20.
rmzalbar
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Re: Dead VIC-20

Post by rmzalbar »

Thanks for coming back on that, the solutions help others. People don't always realize that a capacitor could go low capacitance, leaky, or high ESR even if it looks outwardly fine. Good to hear it's working!
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nefaurora
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Re: Dead VIC-20

Post by nefaurora »

Was your VIC 6560/6561 Chip tested first on a working machine???? The VIC chip is usually the biggest point of failure on VICs...then then the 6502, then the KERNAL Rom....... The VIC can't boot if any of these three are bad... ;)

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WarGames68
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Re: Dead VIC-20 /mod CLEAR VIDEO

Post by WarGames68 »

Hello everybody !

I'm coming back to dig up this subject to send you my opinion on the recent research and analyzes that I have carried out on this S-Video hardware modification of the VIC-20 taken up by the vast majority of VIC20 owners.

Today this S-Video mod is obsolete and inappropriate.

The original Composite signal from the VIC20 just needs to be "cleaned", filtered, reshaped and amplified.

There is a CLEAR VIDEO VIC20 device designed for this purpose, and very simple to install since it does not require any modification or removal of electronic components on the VIC20 motherboard.

This CLEAR VIDEO VIC20 device is placed over the original 6561 video storage.
This obviously makes it possible to separate (dissociate) the 6561 video printed circuit from the entire video part present on the VIC20 motherboard which as you know poses a lot of problems.

Thus, thanks to this CLEAR VIDEO device, you have the choice of either using the Composite signal (optimized, cleaned, filtered, amplified) by adding a 100 pico Farad polypropylene capacitor between the two Chroma and Luma terminals of the CLEAR VIDEO device, either use the S-Video signal (RGB) without this capacitor (see link below👇)

Link: https://www.etsy.com/fr/listing/7755539 ... ulateur-rf

Personally I think that Composite is much better suited to the vast majority of TV screens these days.

The S-Video signal is restrictive in particular because it has an S-Video cable manufactured specific to its equipment (retro-gaming game console).

I confirm that it is useless and obsolete to touch the electronic components of the VIC20 and even the C64 to improve and optimize the video display on the screen.

Thanks to this inexpensive device (40€), if you still have a bad display, then the problem comes from a defective component of your machine (VIC20/C64).

Another important element, if you are still using the old VIC20 power supply, be aware that the voltage levels are not stable and can cause anomalies/parasites carried in the video circuits of your machine.
It is therefore preferable to install a VIC20/C64 power protection device.

Kind regards.😉
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