National tone control circuit
 

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

--
Say no to institutionalized interference.
Just say NO to HD/IBOC!

National tone control circuit
 

Well, how about starting with the motorboating, and checking the decoupling
caps?

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

National tone control circuit
 

"William Sommerwerck" wrote in message
. ..
Well, how about starting with the motorboating, and checking the
decoupling
caps?



All caps have been replaced. I even doublechecked all my connections to make
sure I didn't err installing any of them.

National tone control circuit
 

"Ken" wrote in message
...
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

Negative feedback circuit is OK.. if I switch the polarity, it howls like a
banshee.. :)