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Philco Model 80 Volume Problem - Printable Version

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Philco Model 80 Volume Problem - 1guitrdude - 10-18-2011

Hi All,
New to the board and looking for help. I have a Philco Mod 80 I'm fixing for an elderly neighbor. I have a little tube guitar amp experience but new to tube radio's. I replaced several caps with newer caps and got it working but the volume swells after running about 2 minutes and I'm afraid it will damage the speaker. Once it swells there is no volume control at all. Any suggestions? Any help would be greatly appreciated...

Re: Philco Model 80 Volume Problem - rghines1 - 10-19-2011

I think you are describing motorboating or oscillation.

Regeneration adjustment trimmer.
Loose or missing tube shields.
More leaky caps inside those bakelite blocks.
Needs alignment.
Wire dress changes.
Out of tolerance resistors.

http://www.nostalgiaair.org/Resources/843/M0013843.htm

Re: Philco Model 80 Volume Problem - Ron Ramirez - 10-19-2011

The Model 80 uses a regenerative second detector, and the radio does not have an automatic volume control (AVC) circuit. Because of this, volume will normally go up and down, varying with signal strength.

Also, these types of radios (80, 81, 84, 53, 57, 58, 59, 37-84) must be grounded, else the volume control will not operate properly. One convenient (if non-original) way to overcome this is to use a 3-wire grounded cord, connecting the ground wire to the chassis. Of course, this will only be effective if the house is properly wired.

All paper and electrolytic capacitors must be replaced. In addition, all of the resistors should be replaced as well for maximum performance.

Re: Philco Model 80 Volume Problem - 1guitrdude - 10-20-2011

Thanks for the quick replies...will try grounding tonight and replace the remaining caps this weekend. Will let you know how it goes.