The PHILCO Phorum
Potentiometer question - Printable Version

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Potentiometer question - Shaleradio - 07-26-2023

I have the ability to pick up a cannibalized 41-220.  This model was a plug in but no transformer.  There's not much left of it, but I would pick it up if I can throw in a Bluetooth and run new speakers (The speaker is also gone).  The question for the group is this.  My supply would be 12VDC.  Can I use the on/off switch (which is still there) to switch on and off my 12 volt power supply?  Not sure if the old one which was originally connected to AC could do this?
Thanks,
Mark

RE: Potentiometer question - klondike98 - 07-26-2023

I’m not quite sure what you are trying to do but to answer your question, yes the on-off section of the switch can handle the 12v. Originally the set operated on either 115v a.c or 115v d.c.

The 41-220 will not operate on 12v

RE: Potentiometer question - Shaleradio - 07-26-2023

Thank you!  Just what I needed to know.
Mark

RE: Potentiometer question - MrFixr55 - 07-26-2023

Hi Shaleradio,
If I am correctly reading you, you are not looking to restore the chassis but to put a Bluetooth receiver in the radio but to leave the chassis in place for looks, remove the existing power cord and existing wiring from the switch and then to use the radio's switch to power up the Bluetooth receiver. If this is the case, yes, you can do this. However, you cannot power up both the radio and the Bluetooth from the switch in this mode.

However, these are rather simple radios to restore. Are the 2 IF transformers and the oscillator coil still in place. Is the tuning cap still there? Tube sockets still there? If so, there are only about 7 caps and 7 resistors, all of them available. You may have a hard time finding the correct electrodynamic speaker, but any 4" speaker and transformer from an AA5 will work. if you can find only a permanent magnet speaker, connect a 500 Ohm 5 Watt resistor where the field coil should connect to and up the caps to 30 uF. You can power the Bluetooth from a small switching power supply and feed the 120V input from the radio. I will provide more info if you are willing to have both the radio and Bluetooth to function.

RE: Potentiometer question - Shaleradio - 07-26-2023

Thanks for the question.  This girl must have been used for parts because all that remains is the chassis, cabinet and variable capacitor.  I do have a follow-up question, however.  Were all Philco potentiometers made for AC/DC?  Just wondered that as I read the reply.  If not, how would you know??
Thanks .
Mark

RE: Potentiometer question - klondike98 - 07-26-2023

A potentiometer is a variable resistor and in the case of the 41-220 is part 30 in the schematic. See: https://philcoradio.com/library/download/service%20info/yearbooks/1941/split/Part38-Philco%201941%20RMS%20Year%20Book.pdf

The on off switch is part 16. In many sets they are combined into one part. I’m not sure what the case is in your set.

In any event resistors can be used in both ac and dc circuits. The thing that limits their uses is the amount of current they can carry. Same with vintage on off switches which are simply a mechanical device that opens and closes a connection. Hope that helps.

RE: Potentiometer question - Shaleradio - 07-27-2023

Thank you for the follow up!