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

[Carl]

----- Original Message ----- 
From: "Roger" <sub1 at rogerhalstead.com>
To: <amps at contesting.com>
Sent: Sunday, February 07, 2010 2:59 PM
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)
> __


Buy the 470V rated caps (thats whats claimed and marked on them) from 
Ameritron to give you some headroom. You could also drop the input AC with a 
fat bucking transformer as long as the filaments stay within ratings.

Carl
KM1H




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