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Old September 25th 07, 12:37 PM posted to alt.binaries.pictures.radio
Ken Ken is offline
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First recorded activity by RadioBanter: Sep 2006
Posts: 68
Default National tone control circuit

Brenda Ann wrote:
This thing's driving me to distraction...

For the longest time, I couldn't get the volume control to work (had been
out of the chassis, and I had no idea how to reinstall it) but I finally
have that working properly.

Now, I can't get the tone control to work. There's no change anywhere on the
control's excursion. It's an active control circuit. As of now, there is a
low level motorboat oscillation with the volume below about half (~10 Hz).

If anyone has seen the circuit before, and can fill in any of the unreadable
parts, please do so.

TIA


If that's the tone control between the 6AV6 and 6BQ5, looks like a
(neg?) feedback circuit. If it got reversed somehow could cause motor
boating. Ken