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Atari with TV tuner card sound problem


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I have a TV tuner card in my computer and I can connect the atari with standard cable with my tv tuner card. When I start frequency scan I end with one channel. There is great picture but absolutely no sound. When I fine tune from 0 to -4 the result wont change. When I fine tune to -7 I have no picture but have sound. Is there something what I can do to have picture and sound at same time?

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I assume you don't have any other TV to test?

If we assume there's nothing wrong with the sound output (it can be tested by drawing sound from source, like it's done if you do a composite mod).

There's a red plastic tower with a coil around it and a ferrite screw inside, like this one:

That's where you adjust the sound carrier, first try adjusting it with a non-metal tool - as a metal tool is likely to crack the ferrite as well as mess up the setting when removed if you happen to find a setting that works.
This adjustment can be reached through the lid of the metal case if there's one of those around the motherboard.

If you have tried turning it all the way down and all the way up (while running something with sound) and still get no sound you probably need to replace the two polystyrene capacitors in the sound circuit, they drift over time and finally so bad that it's no longer possible to adjust the coil enough to compensate for this.

They're 820pF, can be bought (could have if they weren't sold out) here for example:



As you can see in this image there's a pair and they're closed to that coil with the red plastic:



If you don't have $1-10 to spend on a pair of new caps then try to change the coil value instead as I did here:


A few turns of cable hooked to the thin-wired coil to get the sound in the right area again.
Click the image to zoom.

No matter what method you choose you still need to twist that ferrite screw so be sure to get or make a tool that fits. A wooden or plastic pin of some sort for example shaped to fit.
It's allowed to use professional tools if you have such.

Other pages on the same problem:

Edited by e5frog
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Thank you a lot for great answer. Worth to keep it for future. Anyway I have tried the red tower. I have screwed it down as far as I could. There was some change, but not big. So I have tried to screw it all the way up. And sound was magically there with picture. So happy it worked. Thank you. So problem is solwed.

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