Recapping the VIC 20, plus bonus SVideo.

I had a bit of spare time yesterday and I wanted to do something, anything to distract myself from all sorts of “stuff” going on at the moment.

I figured I was well overdue to recap my VIC 20. The picture from it was pretty awful, so I was hoping it would fix it.

What you can’t see… All the annoying shimmer.

Thankfully the VIC 20 has a grand total of 6 electrolytics, and I’d ordered replacements ages ago and just needed to find them again. Diving into my big bin-o-components, I was able to pull out all 6 needed capacitors.

I fired up my desoldering gun, desoldered the first side of the first capacitor and “brrrz”, the soldering gun jammed. Gah!
It does this quite regularly, so I know exactly how to unclog it, but it’s still frustrating each time.
This is a ZD-915, and they are a little prone to blocking. If anyone else finds theirs jams, here’s my solution

  1. Turn off the unit and let it cool.
  2. Remove the glass solder collector. Probably time to empty it anyway.
  3. Turn on the unit again, and get a soldering iron. Set both to about 360°C and let them heat up
  4. Insert the cleaning rod in as far as it will go. Mine usually blocks at about an inch left to go.
  5. Coming out of the back of the desoldering gun into the glass solder collector is a small metal tube. This is what is blocked. Gently touch the soldering iron to the back of the tube while pushing on the cleaning rod.
  6. After a few seconds, the cleaning rod should push the blockage out and you’ll be able to clean the tube thoroughly.
  7. Turn everything back off and let it all cool.
  8. Reinstall the glass solder collector. Start everything back up and continue desoldering.

So 30 minutes later I had the desoldering station cleaned again, and removed all the other caps. Some are beneath the RF shield, so you’ll need to pop that off too,

“Dead” caps. Probably mostly fine, but after 30 years, the electrolyte aint at it’s finest.

Once they were all gone, I started replacing them, one by one, making sure to observe polarity and make a nice neat job of it. The new capacitors, despite being exactly the same rating as the older ones, were all marginally smaller. Thankfully no “surprise! incorrect polarity!” on the motherboard markings, but I had made a note of polarity before I started, just in case.

And the video was exactly the same.

What you can’t see is all the annoying shimmer, still.

Now I had been planning, for a while, to modify it for SVideo, as the picture improvement was supposedly much better. Unfortunately I needed some bits-n-pieces and I didn’t have the car so I had to wait until today to get to the store and buy the parts.
I needed an additional capacitor, resistor, DIN 5 plug and a mini DIN 4 (SVideo) socket.
For cable I used some leftover USB lead I’d salvaged, as well as some figure 8 cable for the audio. I also had a RCA socket spare.

Firstly I modded the VIC 20 end. That was as simple as desoldering a ferrite bead and a capacitor. (The cap looked suspiciously like a resistor). You then cut two tracks and wire across a fly lead. Finally you replace the ferrite bead with a 100nF cap and the “capacitor” with a 75Ω resistor. This went smoothly, although I replaced my fly with a thicker wire later. I’d originally used kynar again, but, as we’ll see, I had problems, so I’d replaced it as a precaution.

The top side. The mod is just above the chip in the picture.
The underside. the flylead is visible. At both ends is a cut trace.

Onto the video cable. Checking carefully, I soldered everything together, checking at the end pf the process, that everything was on the correct side. Glad I did! I’d managed to get the soldering on the DIN 5 completely backwards. That would have been bad, as one of the pins carries 5v and would have been running that into the audio lead. I neatened everything up, insulated leads with a mix of electrical tape and shrinkwrap, and buttoned everything up. I prefer to use shrinkwrap, but sometimes, there’s not enough space.

The video cable. I use sockets as it means I can have a lead from behind the TV and don’t need to reach around to plug / unplug anything.

Plugging in the cable and turning on the board produced… not good video.
Unplugging, I started inspecting my work. I noticed that the original mod had a component in one of the pictures that had been positioned slightly different to that in the original article. I tried moving mine to the same location as the picture, and… it worked. Boy howdy did it work. It’s crisper than my C128D.

Not present: Any annoying shimmer.

I tried all my games and all produced a lovely picture. About the only issue I see is some are producing slightly off synch and sometimes the picture is not centered on the screen. I suspect this is an artifact of the VIC 20 or the TV, not of the SVideo mod. I’ll try a different TV shortly.

A classic game. Looks great!

[EDIT] Clockmeister has helpfully pointed out that apparently that centering issue is a feature not a bug. Apparently cursor keys will allow me to adjust screen position. I’ll have to try it out.

Published by ilike8bits

I collect old computers and consoles

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