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In Reply to: RE: Losses in Output Transformers posted by Triode_Kingdom on September 15, 2021 at 12:48:44
Won't the RMS voltage at one anode times the average DC current through the cathode resistor (minus screen current) for that tube equal 1/2 the power being delivered to the transformer? Or will power factor or other issues get in the way of this simple measurement? There's not much phase shift through the transformer at these frequencies, so I wouldn't think its reactance would create a problem.EDIT: The current measurement would need to be AC signal current, not average DC. In fact, it might be necessary to insert a low-value resistor in series with the anode temporarily and calculate anode current by measuring the AC voltage drop across that. Otherwise, signal current into the screen would skew the result.
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Edits: 09/17/21Follow Ups:
I made a measurement with the amplifier running at 60 Hz (a frequency that ensures the accuracy of my DVM). With 25V RMS on one anode (which would be 50V anode-to-anode), the loaded 8 ohm tap of the output transformer produces 1.77V RMS. Based on the 6.6K:8 impedance ratio of the transformer (give or take), the secondary should produce 1.74V RMS. This would certainly appear to indicate that the transformer is not the culprit.
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