NTSC VIC-20 to PAL Conversion: Anybody know the electrical equivalent to my index finger???

[DistantStar001]

I know this is an odd title. But I swear I'm for real. I'm in the process of converting my NTSC VIC-20 to PAL. I managed to install/swap all the components using this site as a guide: http://blog.tynemouthsoftware.co.uk/201 ... rsion.html

Having followed these instructions, my VIC-20 produces a stable picture, but depending on the screen the color is either unstable or monochrome. That is unless I bridge the leads between R9 and FB7 with one of my fingers. Then the picture is perfect on all my PAL compatible screens. So it would appear that I LITERALLY need the electrical equivalent of my finger tip to get this to work. However, it's kinda hard to use a computer if my hand has to be constantly stuck inside it. Any ideas?

[groepaz]

In situations like this, the finger/body acts like a capacitor kindof.

In any case, when color goes off like this, the color carrier frequency is slightly wrong - you'll have to adjust it with one of the pots. Better have measurement equipment for this

[DistantStar001]

In situations like this, the finger/body acts like a capacitor kindof.

In any case, when color goes off like this, the color carrier frequency is slightly wrong - you'll have to adjust it with one of the pots. Better have measurement equipment for this

Thanks, pointing out that my finger was acting as a capacitor helped. Turns out I had soldered the axial capacitor that runs from FB7 to R10 to the wrong spot, linking it R10 to what turned out to be R9 instead. I moved it over, and with some adjustment to R10 the picture is both stable and colorful now!

[JonBrawn]

In situations like this, the finger/body acts like a capacitor kindof.

In any case, when color goes off like this, the color carrier frequency is slightly wrong - you'll have to adjust it with one of the pots. Better have measurement equipment for this

IFF you find you need to adjust the trimmer capacitor to correct for a color issue (most of the time you don't, but this would be one situation where you might have needed to) then you could use a really expensive high accuracy frequency counter, but that isn't necessary - hook up your monitor and twiddle the trimmer until you get correct color, advance it until the color goes wonky, go back the other way through the good section until the color goes wonky agains, then set the trimmer to the middle of that range. If it looks like correct color, then it is correct color.

The trimmer capacitor is near the crystal (small metal can), and requires a small nonmetallic flat bladed screwdriver to adjust it; some of them are soldered in position, you need to unsolder them quickly to prevent damaging the device.