Vic is now grey

Exin · Post by **Exin** » Fri Sep 02, 2011 9:32 am

Hi there.

The colors of my vic are now suddenly grey.
Before, after a few minutes the colors suddenly popped back now that won't happen anymore...

I feed the vic with 5V from a PC PSU since i don't have a 9V one that is powerful enough to power the vic.

Its a Pal one.

Is it common? I tried alot of different things except working on the motherboard itself....

-exin

tokra · Post by **tokra** » Fri Sep 02, 2011 11:11 am

My own VIC starts out grey sometimes and will only go to colour after a few minutes or if I just toggle the colours randomly:

Code: Select all

0 poke36879,rnd(1)*256:run

After some seconds it pops to colour then...

Post by **Jeff-20** » Wed Sep 07, 2011 8:03 pm

A while back I was really working hard trying to make my VIC display gray!

Boray · Post by **Boray** » Thu Sep 08, 2011 4:24 am

You need to adjust one of those little adjustment screws inside of the vic-20 located near your vic chip.

Leeeeee · Post by **Leeeeee** » Sun Sep 11, 2011 2:32 pm

It can't hurt to try C48 on a DIN VIC or C32 on a two prong VIC.

It's the one nearest the XTAL.

Make a note of where it is before you start. Use a non conductive tool if you have one.

Lee.

e5frog · Post by **e5frog** » Mon Sep 12, 2011 10:04 am

Are you feeding the VIC 5VDC only?

I read recently that you can feed a VIC 20 CR (the one with the circular DIN power connector) with 12V on the 9VAC pins.

Do you have the "two prong" or VIC 20 CR?

If you have the two prong version, I hope you feed the 5V after VR1 or some other clever location.

The 9VAC is really only used for the datassette motor and output on the user port, right?

Start by turning up the color on your TV/monitor and maybe try it on another TV/monitor just to check it's not that. Tuning the TV might help (if you use RF).

Boray · Post by **Boray** » Mon Sep 12, 2011 10:26 am

e5frog wrote: I read recently that you can feed a VIC 20 CR (the one with the circular DIN power connector) with 12V on the 9VAC pins.

Why would you like to do that?

e5frog · Post by **e5frog** » Mon Sep 12, 2011 12:17 pm

For the obvious reason... if you don't have a supply that fits and you perhaps have a PC PSU or Amiga PSU or other - that has +5V and +12V.

Not something I'd like to do, just something that's possible - just like you can run a NES on DC voltage even if it originally has an AC adapter.

It looks like +5V is enough though but you can't use the datassette if you do.

Another thing you might want to try is to re-seat the VIC-chip, if there's too much oxidation between pin 2 and it's socket (if any) it might be a problem. Possibly one of the caps is broken but that's not a very common problem. Adjusting the pot/s might help as mentioned.

Exin · Post by **Exin** » Sun Sep 25, 2011 6:41 pm

Anyways thanks for the hints.

The TV set i was using was the culprit.

This is the se second out of four displays that doesnt show color with the vic.

`The other is a Mitsubishi Multisync with additional composite video.

Leeeeee · Post by **Leeeeee** » Mon Sep 26, 2011 4:27 am

The TV set i was using was the culprit.

Unless the sets have stopped displaying anything in colour it is still more likely to be the VIC.

Lee.

RJBowman · Post by **RJBowman** » Tue Oct 25, 2011 10:43 pm

Somewhere between the VIC chip and the video connection to your television, the luminance and color signals are carried by separate wires. If the color wire is broken or disconnected at any point, you won't see any color.

e5frog · Post by **e5frog** » Wed Oct 26, 2011 5:21 am

Isn't there a frequency adjust knob somewhere that affects the color encoding frequency as well?

Exin · Post by **Exin** » Sun Nov 27, 2011 2:55 pm

Well, i found it out already. Its definately the TV. The Mitsubishi also doesnt show colors and the NEC one only after a while. On the CBM Monitor the colors are just fine.

Mike · Post by **Mike** » Sun Nov 27, 2011 4:34 pm

The colour carrier frequency is coupled to the CPU clock. It is most probably de-tuned on your VIC-20.

Some TVs accept a wider deviation of the colour carrier frequency from the ITU norm, others don't. If your VIC-20 is outside that margin for a given TV/monitor, you only get a grey picture.

I'd recommend setting a frequency counter on the clock generator. Adjust the circuit to the correct frequency just as the VIC-20 has been started, mark that position on the variable capacitor, then do the same after warm-up (say, 20 minutes), mark this position also, and then set the capacitor to the middle of the two positions.

Then you have good chances you get colour on all 3 displays, right after start-up, and also when the VIC-20 has warmed up.

e5frog · Post by **e5frog** » Mon Nov 28, 2011 7:55 am

Yes, or your oscilloscope or maybe other >$1000 equipment that people with VIC-20:s usually have.

If you make a mark of the current position you could try small adjustments and see if you get any color, if it doesn't work out then just set it back to the original position and forget about the tricky TVs.