PHILCO 20 - VOLUME - Printable Version

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+--- Thread: PHILCO 20 - VOLUME (/showthread.php?tid=23900)

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PHILCO 20 - VOLUME - ducretet - 11-08-2022

Hello,
The volume of the Philco 20 is made up of two resistors, one 250 ohms and the other 5,000 ohms.
The 5,000 ohm one is bad.
How could it be fixed?
I'm afraid to open it.
Any suggestions would be welcome.
Thank you

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RE: PHILCO 20 - VOLUME - Radioroslyn - 11-08-2022

I had a similar issue with an early model 70. The 500 ohm section controls the rf gain via the cathode circuit. The 5K side is to eliminate signal on the ant when the volume is turned down. This stops any reception when the volume is lowered.
I disconnected it and made a resistive divider that would quite the set with the volume down and it tuned to a moderate signal. It does lower the sensitivity but it's negligible.

GL

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RE: PHILCO 20 - VOLUME - ducretet - 11-09-2022

Hello,
The section that controls the RF gain across the cathode is the 250 ohm section. This section is fine.
If I understand correctly, I have to disconnect the terminals of the 5,000 ohm section. And then? What do I do with the three terminals? I don't understand exactly what you are proposing.
Thanks again

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RE: PHILCO 20 - VOLUME - Radioroslyn - 11-09-2022

Ok With the 5000 ohm section out of the circuit and the volume turned down do you hear any stations? If not you don't need the that 5000 ohm section in the circuit. If so clip lead in a separate 5000 ohm pot where the bad one was and adjust it till you can't hear any stations. Measure the resistances from the wiper to each end and select 2 fixed resistors that are close to those values. This is to mimic the pot. Wire in the same the clipped in pot was.

The lower you set the volume level with this clipped in pot the lower the overall sensitivity will be. That the design of the circuit so it a bit of a balancing act to get where you like it. Hopefully you don't have a very powerful station close by.

GL

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RE: PHILCO 20 - VOLUME - ducretet - 11-09-2022

Hello,
I have put two resistors: 2K2 and 1K8. And volume working.
Thank you!!

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RE: PHILCO 20 - VOLUME - radiorich - 11-09-2022

Hello Ferran,
Nice repair !
Sincerely Richard

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RE: PHILCO 20 - VOLUME - Radioroslyn - 11-09-2022

Glad you got it working!
And it's been my pleasure.

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RE: PHILCO 20 - VOLUME - ducretet - 11-09-2022

Thanks Richard and thanks Terry for the help.
Regards,
Ferran

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