If one cap gets leaky after some use then then whole set is lost.
It occurred to me that the idea of having the HV series metering resistor
distributed across the
capacitors is perhaps useful besides equalizing the voltage between them, you
would have to do that
anyway. But if one day you turn on the amplifier and the HV reading increased
significantly, it is an indication of a
shorted capacitor. But I always felt that you need at least one extra capacitor
breakdown voltage safety margin
in the capacitor bank.
73
Bill wa4lav
________________________________________
From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
Roger [sub1@rogerhalstead.com]
Sent: Sunday, February 07, 2010 2:59 PM
To: amps@contesting.com >> Amps Amps
Subject: [Amps] Converting a 76A to a pair of 3CX800's
As I mentioned in an earlier post, I need a 3CX400. If I don't find one
I'm considering converting to a pair of 3CX-800's which I already
have. Although I'd have to replace the transformer as the one in there
is a bit on the light side and there is little room for a filament
transformer. That's notably less than the cost of a new tube. The
conversion looks straight forward and quite simple as the new
transformer has the proper filament voltage (IOW it's a drop in
replacement with the filament winding for the 3CX-800's) ...BUT, when I
look at the transformer with a 1900 VAC RMS winding into a full wave
bridge and then at that stack of 6 450 V caps it looks a bit marginal.
IOW 1900 X 1.414 - 2686 volts out of the bridge while 6 X 450 = 2700 V
for the capacitor ratings. If I figured that correctly that's a whole 14
volts to spare if all the caps are at least 450 volts.
Any thoughts or suggestions?
73
Roger (K8RI)
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