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reducing B+

12/11/1999 3:12 PM
reducing B+
hey all, can anyone recommend any alternative  
methods of reducing the "B+" coming outta' a  
BF Bandmaster power tranny - besides the zener diode trick?  
I installed 3 24volt 5 watt zeners in series off  
the center tap and reduced the B+ from 452VDC to  
about 396VDC -BUT- the darn 72volt bias tap circuit  
behaved very weirdly .. using the standard 10K-L pot  
and a 22K resistor from one side to pot chassis  
ground the negative volrage available read from -31  
to -56 vdc, but I could not get anything more than  
7.6ma of bias current through the power tubes (4 6V6GT - in a 5F8-A Twin circuit), after removing the zeners,  
the bias swing available was -67 to -28vdc and I easily  
able to gewt about 22ma per tube- problem is I feel  
like I am killing those poor 6V6'ers with aroung 452 volts on the plates. helllllllppppp :)

Ken Gilbert Put the zeners back in.... -- 12/11/1999 4:09 PM
Dave H. You could put the Zeners in the pos... -- 12/13/1999 2:32 PM