41-295 tone potentiometer - Printable Version

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+--- Thread: 41-295 tone potentiometer (/showthread.php?tid=2567)

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41-295 tone potentiometer - John R - 09-09-2010

Good evening,
The R53 tone pot shows as 4 Meg on the schematic but also has 400K written just above the 4 Meg. Is this a drafting error or does it imply that the tone control shaft mechanism should be adjusted so that the minimum resistance should be 400K? Have not seen this before? The tone pot actually measures around 8 meg and appears to be part # 33-5335-1 instead of 33-5325 listed in the parts list?
Is the pot linear of audio taper?
So far have replaced 21 caps., 17 resistors & will replace an open audio output transformer & broken on/off switch. Have these two parts on hand. I am leaning toward being prudent and leaving the pot alone as the 4 thumb wheel mechanisms work well. Have the P.B/tunning unit disconnected from the chassis to replace the on/off switch, "rubber" insulated wiring and clean up as the radio was the home for kitty kats for an extended period of time. How do you get that smell out? The tone pot question would apply to 41-300 & 41-315 units also since they share the same chassis.
Thanks for any assistance.
John

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Re: 41-295 tone potentiometer - Ron Ramirez - 09-09-2010

I would leave the pot alone unless it is obviously faulty. Some of these were 6 megohms, others 4, still others had a 6 meg section and a 400K section. The ones with the 6 meg and 400K sections often read open, but work in the radio.

If you look really close at some 1940-41 Philco schematics with this type of tone control, some of these are drawn with a "break" in them. I think there is a very minor gap in the 6 meg/400K controls. And, yes, they will work that way. One section cuts bass while the other cuts treble. When the wiper arm is closest to the plate of the first audio tube, treble cut is at maximum, giving the effect of more bass. And with the wiper arm at the opposite end of rotation, close to the resistor connected to the volume control tap, bass cut is at maximum, giving the effect of more treble.

If it is scratchy or does not seem to be working, try a shot of DeOxit first before thinking about replacement. That one would be very difficult to replace since it has a metal gear attached to the shaft; this metal gear makes contact with "teeth" on the inside circumference of the tone control thumbwheel.

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Re: 41-295 tone potentiometer - John R - 09-11-2010

Ron,
Thanks for the info. It clarifies the schemo. I believe what I have is the straight 6 meg. pot. Will not mess with it as after looking at it closely it would be a major task to replace due to the drive shaft as you said.
After cleaning up and repairing the P.B./tuning unit am going to repair the broken band switch. Should be quite the task as the B wafer is broken so need to remove both the A & B wafers to install a new B wafer. Will take my time and document closely.
Just got a second 41-295 chassis/speaker in yesterday for parts to do this. After I get the radio working I will have a spare chassis and speaker. If anyone needs hard to get parts for the 41-295/300/315 series I will give them any items once I get my radio operational again.
Thanks for the help.
John

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Re: 41-295 tone potentiometer - Glenn Roberts - 10-18-2010

John,
Sounds like what I'm going through with my 41-300, luckily the dial switches seem in good working order, but the wiring is tedious. I would be interested in any leftover parts you may have after your restoration is complete. Just PM me. Thanks.

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Re: 41-295 tone potentiometer - Ron Ramirez - 10-19-2010

John,

How is the restoration of your 41-295 coming along?

I would be interested in the extra audio output transformer if it is good, and if GlennPR does not want it since he asked first for parts.

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