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Antique Radio Technical Forum
A Volume Pot Question Now

Posted by Doug Criner on 04/16/2009 19:17

Here's the schematic: http://www.nostalgiaair.org/PagesByModel/417/M0013417.pdf

The resistance across the whole shebang should be 2M (between ground and the top of the 50-uuF cap).

There is a fixed tap in the center of the pot that goes to the bottom of the 50-uuF cap, and then the wiper that is connected to Cap #43. You should measure 1M between the fixed tap and the two ends of the pot. I think it would be impossible to have 2M across the whole pot and also 2M across each end to the fixed cap. Maybe I shouldn't say "impossible," but I can't see how it could be.

You are measuring the resistances with the pot removed from the ckt. If you were measuring it in the ckt, maybe you could conceivably get some funny business due to sneak circuits.

If I were a betting man, I'd say your pot is probably good.
Doug

:Do you mean fixed tap? Resistance to the center tap normally isn't specified because it is variable.
:
:In any case, readings from the outer legs to the tap should equal the total reading across the outer taps.
:
::Hi! So I'm still debugging the Philco 41-285. I've got the volume pot isolated, in fact completely out of the radio. It is the original pot according to the part# on it and the parts list. Schematic says it should be 2meg total and 1meg from outer legs to the center tap. On mine it rades 2meg across the pot but it also reads 2meg from each leg to the center tap. Is this pot defective?
::Thanks, Johnny



A Volume Pot Question Now 
Johnny 04/16/2009 16:34 
Rene 04/16/2009 17:53 
Doug Criner 04/16/2009 19:17 
Johnny 04/16/2009 21:29 

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