[Amps] Questions on hot switching 2700V B+ to a 3CX800 amp.

Tom W8JI w8ji at w8ji.com
Sat Aug 12 12:55:05 EDT 2006


>    I have long been disappointed on the noise and 
> mechanical vibration
> noises created by these puppies.  They also get quite warm 
> just sitting
> there idling, I think mainly because of the heavy bleeder 
> resistors across
> the filter caps.

Mike,

How much power are the bleeders actually dissipating? Did 
you ever look at that?
I'd know that first before planning anything.

The things I'd learn are the power in bleeders, the power to 
run the blower, and the current draw off the power lines 
during idle. That would give you some idea of the payback 
for the work.

Personally, I'd never switch the HV off and on at short 
intervals. You should never apply RF drive to a cathode 
driven amp without HV being present. With a 3CX800 the grid 
current surge could eat up the tubes.

73 Tom 




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