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Threads: 1
Joined: Oct 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...
Posts: 190
Threads: 8
Joined: Oct 2005
City: Lexington, SC
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
(This post was last modified: 02-27-2012, 05:03 PM by
rghines1.)
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
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.
--
Ron Ramirez
Ferdinand IN
Posts: 2
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Joined: Oct 2011
Thanks for the quick replies...will try grounding tonight and replace the remaining caps this weekend. Will let you know how it goes.
