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previous: Ted Pimm Re: Stromberg-Carlson P.A. (hamfest finds) -- 6/14/2000 9:11 PM view thread

bias measurement with no SG resistors

6/15/2000 1:38 PM
Ted Pimm
bias measurement with no SG resistors
Ok, having a hard time measuring bias via transformer shunt and I assume that's because I have no SG resistors in this amp.  
 
I measure a voltage drop of 37V across the 250ohm cathode resistor (unbypassed). Plate volage is 430V. I calculate using ohms law that there is a total of i = v/r = 148 ma which should equal screen and grid current, correct? Does this sound reasonable?  
 
Very interesting circuit similar to earliest Fender amps with 'paraphase' PI (6N7 tube).