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Bias supply ??


 
7/25/2000 3:39 AM
Cliff
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Bias supply ??
Is is safe to use the negative side of the SS rectifier(s) for a bias supply ?If not, where can I get it from without adding a whole lot of extra crap...PT doesn't have bias supply wire. thanks
 
7/25/2000 12:44 PM
K Bullion
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Hey Cliff, It doesn't matter where you take it from however this is not the supply to be careless with. The bias is probably the most important of all. A failure in this supply could cost you an output transformer. Keep the supply impedance about one tenth of the grid-leak resistance and you should be ok ! Good Luck, K Bullion
 
 
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7/26/2000 12:49 AM
Brian
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Do you mean the diodes off your HV winding on your PT?  
 
NO.  
 
There is AC on the anodes of your recifier diodes.  
 
The bias supply should either come from a separate tap, or just run a diode backwards (cathode towards the transformer) off of one of the two HV taps.  
 
Run that to a filter cap, and then to a pot to ground. Well, you might want to have a resistor in series with the pot if your winding is too hot. You never need -250V of bias, and your 0.5W pot may not like that :)  
 
Fender usually used 50uF for two or 100uF for four 6L6, and the pot was 10K. In your case you will probably have a lot more than 50V available though using the HV tap.  
 
BT
 
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