[Amps] Converting a 76A to a pair of 3CX800's

[Fuqua, Bill L]

  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 at contesting.com [amps-bounces at contesting.com] On Behalf Of Roger [sub1 at rogerhalstead.com]
Sent: Sunday, February 07, 2010 2:59 PM
To: amps at 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)
_______________________________________________
Amps mailing list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps