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I bought a 1977 Gracia Color Video Game TVG 432 (not much to be found online), image from 20th Century Video Games:

Gracia TVG432

enter image description here

And the unit works, but the video signal is kind of sketchy.

It is not very strong, and when I fiddle with the board, it changes in quality (up to near perfect image). My TV's auto-tune has trouble finding the signal (channel 3). My flat screen digital TV doesn't find the signal at all.

enter image description here

Is there anything I can do to troubleshoot or repair this?

Update There is a "Fine Tune" dial that already helped a lot. Still when handling the board, the signal flickers.

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  • 1
    I am not voting to close, but this may be more suited for Electronics. Commented Jan 21, 2023 at 11:23
  • May need to replace old capacitors.
    – Jon Custer
    Commented Jan 21, 2023 at 15:22
  • I've seen many televisions which seem to auto-tune when switching to a channel, but then keep whatever frequency they locked onto. When using devices with RF modulator outputs, I've sometimes found that switching to a different channel and then back can help a lot.
    – supercat
    Commented Jan 21, 2023 at 17:46
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    Re, "...digital TV doesn't find the signal at all." Are you certain that your TV is capable of decoding analog TV signals? If it is capable, is it possible that you're trying to tune cable channel 3 instead of over-the-air channel 3? Commented Jan 21, 2023 at 19:45
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    What eactly does "fiddling with" and "handling" the board entail? The RF modulator might already be a bit wonky, since you need to fine tune. I guess it is in the bottom right-hand part of the board. Touching it anywhere around that part might effect it and throw it out of what even further. I see a variable capacitor and resistor down there, which suggests that you might be able to tune it (with a special tool). Take some higher res pictures of that area (so the markings of the chips can be read) and also one of the reverse side. (I'm no expert tho)
    – Dan Mašek
    Commented Jan 21, 2023 at 21:27

1 Answer 1

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The main thing is that the signal changed when you handled the board. That implies to me there’s a loose connection (or more than one). See if you can figure out which it is:

  • wiggle each wire
  • inspect the solder joints
  • check all potentiometers and switches

Depending on which one, the fix could be easy. Resolder wires and dry solder joints, or deoxit the switch/potentiometer.

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