Vic 20 issues

[scotty]

OK, SO i dug 2 Vic 20's out of my storage locker. Been in there at least 10 years. No idea how in the hell they got in there, but I knew they were there. Got the itch and ordered a Final Cart III for the Vic 20, so I figured I would go get the Vic's out of the locker.

Both are the old style with the Black and white label, and the 2 pin power connector. I working power supply and 1 RF modulator.

Vic 20 #1 no video. Power LED comes on, sends a video signal, but no video. Reading online, found out it is usually the VIC or the kernel that is bad. Also possibility of a bad ram chip. Tried with both RF Modulator and known good composite cable.

Vic 20 #2 works great. Using RF modulator on modern TV, correct colors, but a little hazy, as to be expected from an RF on a new TV. After a few minutes, I get Yellow marks running down the borders on both sides. Nothing in the main screen, just down the light blue borders. Using the 5 pin din composite cable, looks a lot better, but colors are off. Yellow also starts running down the side.

After a few minutes lines have went away!! Woohoo!!! Amyhpw, here is a pic with the compisite video cable. NOTE: Vable works fine on Atari 8-bit and c64c.

http://i66.tinypic.com/8wl16w.jpg

[carlsson]

The image doesn't display for me, perhaps something is wrong with my computer.

 

Close to the VIC chip, there are trim pots/caps of which I believe at least one is for saturation. Video quality differs a lot between each VIC-20, but if it looks washed out or overly saturated in composite video either try to adjust the settings on the TV (easiest, safest) or look up those places that you're allowed to adjust. I don't know the cause of the yellow marks. Do they disappear again after another couple of minutes?

 

Did you go through this troubleshooting checklist? There is a 7402 at UB9 that could be worth checking, perhaps the crystal at Y1 too.

http://personalpages.tds.net/~rcarlsen/cbm/vic20/vic20.txt