Posts: 6
Threads: 3
Joined: Jul 2017
City: Pawnee,IL
Hi,
I just rebuilt a 41-280. Replaced ALL wiring ,even in the IF cans,resistors and caps.The BC band is working great and all tube voltages are right on.I was getting ready to do a IF and RF alignment
My question is, at min. volume, the audio can still be heard. I have even grounded the wiper on the pot and the audio is still there.It is not loud but, can be heard.It is leaking past the pot somewhere.
It doesn`t take much of a turn to get the volume pretty loud.
Posts: 7,295
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
The that thing comes to mind is it could be internal leakage in the det/1st audio tube. Have hear it a lot with sets that use 'at6 and 'av6 tubes.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 6
Threads: 3
Joined: Jul 2017
City: Pawnee,IL
That makes sense. I even tried another 7C6 with the same problem.I`m sure the customer will want zero audio with the pot turned all the way down. Should I try putting in a resistor in series with the green secondary IF to the diode?
Posts: 6
Threads: 3
Joined: Jul 2017
City: Pawnee,IL
If I ground the grid on the 7C6 no audio.They are using -.6v bias there.
Posts: 7,295
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Try grounding the DIODE plates on the 7C6. It's not really the det tube it's hooked to the avc line.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 03-10-2021, 05:50 PM by
Radioroslyn.)
Posts: 6
Threads: 3
Joined: Jul 2017
City: Pawnee,IL
Hi,
If I ground out the diode plate (pin 6)with the green secondary wire from the IF can it is dead quiet.No audio is heard at any volume.
If I ground out pin5 the audio is reduced but still there. If I ground the blue secondary wire from the IF can the audio is low but still there.
I even wired in the volume control circuit from a 42-360 and still cannot mute the audio when the pot is turned down.
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