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What function do these resistors provide?


 
1/19/2006 1:38 PM
bennypapa
What function do these resistors provide?
I am rebuilding a hacked up Fender bassman and found some resistors in the power supply that I don't understand. Each of the rectifier diodes is paralleled with a 470k resistor.  
 
Does anyone know what these resistors do for the circuit.  
 
I drew the schematic up  
 
http://web.qx.net/bennypapa/electronics/ganntronPSQUESTIONS.jpg  
 
 
 
Thanks,  
 
Ben
 
1/19/2006 3:16 PM
DirtyGeorge

My guess is that they act to distribute the inverse voltage evenly across the diodes. I have not seen this in other PS designs and I don't know if it is necessary but it probably doesn't hurt.  
 
DG
 
1/19/2006 3:57 PM
Tom Phillips

Each of the rectifier diodes is paralleled with a 470k resistor.  
That was an accepted practice in the early days of solid state rectifiers whenever they were stacked in series to get a higher voltage rating. It was done exactly for the reason DG gave.  
 
IMHO it is not needed with the rectifier diodes currently available. I never have seen a stock Fender built that way so I would say that someone added them to your amp.  
 
Regards,  
Tom
 
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