And a shout out to Enzo who did mention "DC Resistance of the winding" in #19. I didn't connect the dots on that. So thank you.
Last topic on this amp, I wanted to post some notes on the Bias Control for this amp. I guess we refer to this as the non-adjustable fixed bias circuit? Note: I am using JJ 6L6GC 30 Watt tubes.
I made some notes in the picture below. As you can see, the 6L6 tubes are running "cool." I don't see that altering R67 or R58 buy me much. The problem must be that the transformer is loaded such that we can't get the desired -57 vdc at the junction of CR12 and R67. So as we lose voltage across the divider and 220K Control Grid resistor(s), I can only get -52.2v at the Grids. I don't know if the difference of 3 volts would make a substantial difference, in raising the plate current, dissipation, or overall sound of the amp.
I have seen other threads where it was suggested a redesign of this circuitry (some type of full wave negative rectifier) could get you there. After reading your comments on my other thread (Pre Planning For Modifying A Fender Super Reverb Amp), it is clear that "current" in the secondary winding must also be considered. So I don't think this is an option.
Unless someone has a rebuttle, I think this is as good as it gets.
Reference - Rob Robinett Tube Bias Calculator
Last topic on this amp, I wanted to post some notes on the Bias Control for this amp. I guess we refer to this as the non-adjustable fixed bias circuit? Note: I am using JJ 6L6GC 30 Watt tubes.
I made some notes in the picture below. As you can see, the 6L6 tubes are running "cool." I don't see that altering R67 or R58 buy me much. The problem must be that the transformer is loaded such that we can't get the desired -57 vdc at the junction of CR12 and R67. So as we lose voltage across the divider and 220K Control Grid resistor(s), I can only get -52.2v at the Grids. I don't know if the difference of 3 volts would make a substantial difference, in raising the plate current, dissipation, or overall sound of the amp.
I have seen other threads where it was suggested a redesign of this circuitry (some type of full wave negative rectifier) could get you there. After reading your comments on my other thread (Pre Planning For Modifying A Fender Super Reverb Amp), it is clear that "current" in the secondary winding must also be considered. So I don't think this is an option.
Unless someone has a rebuttle, I think this is as good as it gets.
Reference - Rob Robinett Tube Bias Calculator
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