The PHILCO Phorum
Philco Model 20 volume control operation - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Philco Model 20 volume control operation (/showthread.php?tid=7696)


Philco Model 20 volume control operation - SteveJB - 10-17-2013

I cant seem to get an answer on this on another forum. Thought i would ask the Philco experts.

I just finished a recap and resistor replacement. The radio plays well except that the volume is loud even on the low setting. It does get a bit louder as you change the knob setting clockwise as it should though.

I dont really want to use it since I can't adjust it down to a comfortable level. Is this normal for this set? (That is what I would really like to know.)

I do have a spare console chassis that I can scavenge and switch volume controls if needed, I just dont want to waste time if this normal. The one I have in there now looks original.

Did this set have a dial lamp? Mine doesn't, but my spare chassis does.
I thought of replacing it with that one.

Thanks for the advice.

RE: Philco Model 20 volume control operation - keithw - 10-17-2013

On that set the volume control pads down the antenna rather than the audio amplifier. Make sure your volume pot is grounded on the bottom lug. The other thing to do is use a shorter antenna. With a good antenna and a strong station you can get lots of audio with the antenna attenuator (volume control) all the way down.

keithw

RE: Philco Model 20 volume control operation - morzh - 10-17-2013

Steve

the pot is dual, one half divides the antenna signal while another adjusts cathode potentials.
1. measure the values of both sections, make sure they are OK.
2. Make sure the soldering is correct, especially that GND point as Keith just said.

RE: Philco Model 20 volume control operation - Mondial - 10-17-2013

The volume control should be a dual pot. One section, as Keith described pads down the antenna input and decreases the signal level. The second section adjusts the bias on the RF amplifier tubes and sets the level of signal amplification.

It sounds as if the second pot section on your radio is not working properly. This pot is connected as a voltage divider, connected as part of the large wirewound resistor on the side of the chassis. If you connect a voltmeter to the sliding contact of this pot section, you should see the voltage change by several volts as the pot is rotated. If you see no change, then either the pot is bad or there is an open section in the wirewound bias resistor.

If working properly you should have good control of volume level, even on a fairly strong signal.

RE: Philco Model 20 volume control operation - SteveJB - 10-17-2013

Thanks. I will have some time this weekend to check what each of you has said.

RE: Philco Model 20 volume control operation - GarySP - 10-18-2013

Hello SteveJB, later production of these 20's had dial lamps. Yours must be an earlier set. The lamp is easy to add to the dial, and it taps the tube filament wiring for power. Take care, Gary.