The PHILCO Phorum
80 Jr. Volume regulator - Printable Version

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80 Jr. Volume regulator - morzh - 04-09-2012

Well, I gave it a shot.
I opened it up, cleaned it (with alcohol - Varsol seems to be not readily available), used some DeoxIT Greenlabel (Fader Lube) on it.

Where it was the low volume sector, there was bad-bad-bad scratching and the volume would go up (I figured - bald spot), so after cleaning this remained unchanged. I can't have low volume on this thing. After opening, the element did show a large etched bald spot, so obviously through some weird pattern the wiper connects back to a higher resistance part of the scale, increasing the volume, and then, after some really bad scratchy zone, goes almost to zero.

Don't think much can be done.

So, anyone know off hand a replacement part that would mechanically be a good fit? It's a 20K potmeter (don't know linear or logarithmic), with SPST rotary switch.

I looked in Mouser, doesn't look like they have what would fit.

RE: 80 Jr. Volume regulator - LASJayhawk - 04-09-2012

You do have a good ground on the radio, right? My jr does the same thing if the ground wire isn't hooked up.

RE: 80 Jr. Volume regulator - morzh - 04-09-2012

Do you mean if I have the Chassis actually connected to the Earth GND, or do you mean a good connection of the Volume pot to the GND?
The latter I do.
The former I don't.

But the same exact principle (the pot dividing Antenna directly) applies across many Philcos, in my 20 in particular, and it works just fine, and I don't see why not. The divider is there.

RE: 80 Jr. Volume regulator - morzh - 04-09-2012

Just hooked the GND wire to GND in my outlet. Same thing, nothing's changed.

Well, I just paid a bit more attention. With or without GND connected there is a change in volume.
The problem is that where it would be an acceptable volume level while listening to the loudest station, this is where that bald spot is.
So the volume stays very loud, and then goes to almost nothing. But it does change.

I have to tune out a bit, and thus make the station less loud, and then the volume regulation works better.

But...still a new regulator would be better.

RE: 80 Jr. Volume regulator - Radioroslyn - 04-10-2012

Two thoughts come to mind. Try rubbing some pencil lead in the bad area of the control. This may restore the resistive path around the control. Or wire it backwards. As soon as you turn it on turn it all the way up and then turn in down to increase the volume. Works but is a little counter intuitive.
Terry

RE: 80 Jr. Volume regulator - morzh - 04-10-2012

Terry,

The last suggestion (wire backwards) was my knee-jerk reaction.
Two cons: 1) the way pot is soldered to the chassis is through a riveted GND contact; wiring backward will be awkward. 2) Exactly what you said - counter-intuitive. Icon_smile

As for rubbing a pencil lead, it is an old technique of fixing potmeters, which I used in my young years (long time ago), but it did not last long enough. If there only were some simple process of graphite application the way they do it at the factory. How do they do it? So it actually bonds?