Vic-20 Pro Tip - Adjust your pots!

[eightbit]

I have been working on these systems (especially the Vic) for many years and it recently occurred to me after speaking with someone with an issue with their video that many people may not be aware that there are video level control and black level adjustments under the cover where the VIC chip resides. Just about every Vic I have worked on would display the video dark and colors off. Why? Well these were set at the factory for optimal use over RF and the way I always displayed the Vic was with 5-Pin DIN A/V cable (composite) for the best possible video out I can get out of a stock Vic.

 

Because I was not using RF of course the video was not set correctly. Luckily there is an easy fix and that is to adjust the pots until you have it right. You can use a small screwdriver but since you would like to do this while the machine is ON (to adjust it and see it while you are doing it) I would suggest some sort of plastic screwdriver if you have one. I never have one but have a steady hand Just a forewarning!

 

The picture I have attached shows two pics from two different types of vics (googled them). The first one that is not labeled is the one I recently worked on. The small red pot (C48) is the hue setting and the white pot is the brightness/contrast level on that model.

 

Just figured I would share this. I realize many people already know, but for the people that do not and think their video is garbage this may be helpful

[channelmaniac]

The small red isn't a pot... it's a trimmer capacitor to tweak the crystal into giving the correct frequency output.

[eightbit]

The small red isn't a pot... it's a trimmer capacitor to tweak the crystal into giving the correct frequency output.

 

 

Good call! I was going to mention that. It is on the cost reduced model but indeed that crystal tweak adjusts hue. A minor adjustment corrected the red, yellow and green on the current system I worked on.

[norm8332]

I suggest you add heat sinks to those VIC chips and leave the cover off. Finding replacements is nearly impossible and they fail quicker with higher temperature swings. Also every 2 prong Vic-20 that I had that had that orange electrolytic cap in the upper left of the VIC RF enclosure needed the orange cap replaced because they were way out of spec. It was always only the orange one. I believe I replaced it on 5 different VIC 20s. Its on the audio output. The audio output still worked but at a lower volume and you could barely hear PCM output.

Edited July 6, 2017 by norm8332

[JiveMega]

So, not being super smart, I think I way over cranked...like kept turning a lot...the trimmer knob.  It didnt seem to do anything noticeable.  The other know fixed everything with minor adjustments but I spun the trimmer a lot both ways being stupid and seen no noticeable change either way.  I was hoping some.verticle lines would leave (they are minor) but didn't.  Did I just ruin this thing or is it okay?