The PHILCO Phorum
Model 96 volume control - Printable Version

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Model 96 volume control - Jonnym - 06-02-2025

Hi all, I am a newby. I own a 1931 vintage lowboy with a model 96 chassis. The volume control works but only goes from medium to loud. It will not allow me to turn it down to a pleasant volume. Can the control be cleaned to fix or does it need to be replaced? I have a cool add for the radio from a 1931 Saturday Evening Post magazine .Thanks!

RE: Model 96 volume control - radiorich - 06-02-2025

Hello Jonnym ,
First all I wanted to welcom you to the Philco Phorum .

As this set goes has anything been done to it recently like any new parts added ?
because if not that might be your issue anyway we would need more information .


The volume control is it scratchy sounding when turned ?

Sincerely Richard

RE: Model 96 volume control - morzh - 06-03-2025

The bottom lead of the vol ctl in 96 is connected to the Center Negative through a 70K resistor (part of an RC filter).
So it is never really at zero vol, but do check that #33 resistor to be 70K or near. If it is much higher or open, the vol will remain high.
https://philcoradio.com/library/index.php/service-info/early-schematics/

Also see if the potentiometer is open. If it is continuous, even 1M or so, it is OK to use. Clean it (it is a wide paper carbonized band with a brass roller as a wiper) without rubbing it with anything: just spray Deoxit F5 (Fader lube) and let dry; DO NOT use contact cleaners like Deoxit D5.

This is my 96 thread from beginning of this year.
https://philcoradio.com/phorum/showthread.php?tid=25548

RE: Model 96 volume control - klondike98 - 06-03-2025

Welcome to the Phorum!
Icon_wave


...and in addition to the annotated schematic that Mike linked to there is the factory schematic info at:
https://philcoradio.com/library/download/service%20info/wiring%20diagrams/vol1/split/Part57-Philco%20Wiring%20Diagrams%20Vol.%201.pdf

Jonnym - Jonnym - 06-03-2025

Thanks everyone, I will pull the chassis out of the cabinet and do some checking. 
  The volume adjustment is not “scratchy”.

RE: Model 96 volume control - Jonnym - 07-11-2025

Hi all, I finally got around to pulling the chassis. My #33 resistor ( part 3542)is getting a reading of 80 ohms of resistance. According to Morzh any reading over 70 is not good. Does anyone know where I could get this resistor part and what the brand and part# would be?
  My potentiometer is the closed type with no openings to clean/lube.                        

RE: Model 96 volume control - Jonnym - 07-11-2025

Sorry for the multiple images of the resistor, I am just learning how to attach files. I did not know the images did not show until you post.

RE: Model 96 volume control - morzh - 07-11-2025

I did not say "higher". I said "much higher".
80K is not much higher than 70K and is well within 20% tolerance.

RE: Model 96 volume control - Jonnym - 07-11-2025

Thanks for your reply!, Could the potentiometer possibly be the problem? Do you know if replacements for them available ?

RE: Model 96 volume control - morzh - 07-12-2025

The potentiometer needs to be checked. It is a very simple check., just measuring end-to-end and comparing it to the required value (it could be within limits, way out of limits, or even open) and then, IF the end-to-end is usable (even if you have 2x the value but no open, it is usable), checking the wiper operation (going from low to high value when rotated, without any interruption).
If satisfactory, it then could be gently dusted with a can of air, and lightly sprayed with F5 (important !!! not D5 or any contact cleaner) Deoxit or a well-regarded taper lube/volume pot cleaner, let dry and then re-checked.

Your pot has cylindrical resistor band inside and a roller-type brass wiper.

As long as the pot is continuous end-to-end (ecven if it is 1M or so) it should work. If your 70K resistor is, as you wrote, 80 (I think you meant 80K, as you wrote "a reading of 80 ohms") and not 70K, while it is OK, but the low volume is too high, you might try to variate the #33 to lower values until you find one that works best for you.

Also make sure this is the case with every station and not just with the strongest local station as often times with older radios (though they used a bit different volume control scheme) that station might come through even with the volume turned all the way CCW. In which case I would leave it be.

RE: Model 96 volume control - Jonnym - 07-12-2025

The two outside leads read open. The middle wiper lead and an outside lead I only get a reading when the knob is turned a third +- up.

Jonnym - Jonnym - 07-12-2025

Bare in mind I am checking the leads while they are still connected to their adjacent wires.

RE: Model 96 volume control - morzh - 07-12-2025

Bear. Bear in mind. Anything smaller than a bear does not fit there. Icon_smile

Now. If it reads open EVEN while in-circuit, it is probably open, and this is why you are having problems.

The resistor strip is held by screws and some clamps: see if you can gently fix it.
If not, get thee a 500K audio taper with a proper shaft (I am not sure the pot is audio, could be linear given how crude the whole thing is) and stick it inside.

RE: Model 96 volume control - Jonnym - 07-12-2025

By “in-circuit “ do you mean while it is still hooked up to the wires?( no power on)

Jonnym - Jonnym - 07-12-2025

Do you think this would work? I would need to cut the shaft shorter.
  Not sure what “40 detents” means.