screen not quite right

geoff0876 · Post by **geoff0876** » Tue Jan 17, 2012 7:16 pm

I haven't started up the vic20 since last spring before we moved to a new house.

Unfortunately when I turned it on yesterday and saw the picture, it was not quite as white as it should be and sort of wavy but not scrolling. You could type and see what you were typing but not really usable otherwise. Whether I connected it to my commodore monitor or tv using, it has the same look to it. I have only the one cable so I don't know if it's the cable or the computer or the power supply.

Any ideas?

Thanks so much,
Geoff

orion70 · Post by **orion70** » Wed Jan 18, 2012 3:41 am

Could it be a video tuning problem? Try (carefully) turning the screws next to the video chip, then test the image with a proper screen like Boray's Testbild.

geoff0876 · Post by **geoff0876** » Wed Jan 18, 2012 6:17 am

Thanks for the tip. I'll try that. However, it seems odd that the video controls would have adjusted on its own. Does that happen? I tried hooking up to two different screens and had the same issue of the screen not quite right.

eslapion · Post by **eslapion** » Wed Jan 18, 2012 12:50 pm

geoff0876 wrote:Thanks for the tip. I'll try that. However, it seems odd that the video controls would have adjusted on its own. Does that happen? I tried hooking up to two different screens and had the same issue of the screen not quite right.

Capacitors mostly will change values over time. Especially if they were left in a humid environment.

The video control will not adjust on its own but you have to compensate for a degradation of the components performances.

geoff0876 · Post by **geoff0876** » Wed Jan 18, 2012 6:44 pm

I sure hope you guys are right. It'd be great if it was just a tuning issue. It has been stored in an upstairs closet the past few months and before the move, I had it out on a desk used sometimes.

Thanks so much!
Geoff

geoff0876 · Post by **geoff0876** » Sun Feb 19, 2012 12:31 pm

I'm trying to find the vic video chip and I don't see it while having the case opened. Is it under a casing? I'm looking for MOS 6560 or 6561 chip, correct? And then I would look for the screws next to it. Thanks so much.

All i've done so far is just use an air duster to blow the dustiness and also vacuum the dust out. Before it seemed like it was just black and white waviness, but now it's black and red it seems with some waviness then finally stabilizing. i stuck in the Gorf cartridge just to see how it would work and you could kind of make out the screen but the colors were all so dark.

Upon vic 20 powered on:
http://img.thegeoff.com/2012/02/IMG_0146.jpg

Screen sort of more stable:
http://img.thegeoff.com/2012/02/IMG_0147.jpg

Screen finally stabilized after a couple minutes but still not correct color:
http://img.thegeoff.com/2012/02/IMG_0148.jpg

My vic20 inside:
http://img.thegeoff.com/2012/02/IMG_0145.jpg

Geoff

matsondawson · Post by **matsondawson** » Sun Feb 19, 2012 3:45 pm

Yes, it's under the metal casing.

p.s. Don't use vacuums on electronics, they produce a static electricity and may zap your components.

Kweepa · Post by **Kweepa** » Sun Feb 19, 2012 4:07 pm

Huh, those colours are totally inverted.
Border is red (R), not cyan (GB).
Background is black (), not white (RGB).
Text is yellow (RG), not blue (B).

Mike · Post by **Mike** » Sun Feb 19, 2012 5:57 pm

Here's what under the casing. Yours should look very similar inside:

It looks as if the emitter follower in the video amplifier circuit has become slightly debiased. You might try to adjust the white trimmer R10 a bit. You should use an isolated tool for that, as a conducting tool can affect the RF circuit and/or lead to short circuits in the cramped space. Remember the original position, so you can revert the adjustment in case it doesn't get better.

I'd leave the hands off the red variable capacitor. It fine-tunes the processor clock and colour carrier frequency. Your VIC shows colour, so the frequency is still inside spec (you'd get a grey picture otherwise).

geoff0876 · Post by **geoff0876** » Mon Feb 20, 2012 11:43 am

Thanks for the tip. Is it tough to get the metal casing off? I don't want to break it.

Yeah, it's definitely weird how the color is totally off.

geoff0876 · Post by **geoff0876** » Mon Feb 20, 2012 1:01 pm

Thanks to you all for the tip the screen is now the correct color and looks good. I don't remember it taking as long to get the screen correct on startup but I guess that's a sign of old age!

However, now the sound is still having a buzz/static/snow sound.

Any ideas on the sound?

It seems it's related to the RF modulator. On the TV I bought in 2006, it works fine, but on a TV bought a few years before that, which I'd really like to use with it, it pretty much has no sound. I tried it with the same cables. I thought for sure I used to be able to use this before. I would prefer even using it with my commodore 1702 monitor but I have no idea if that still works since my C64 power supply is fried.