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

[Dave Hachadorian]

The AL-1500 has a stack of eight 450V caps, and a plate voltage 
of 3600. 8x450=3600, so Ameritron didn't leave any headroom 
there. The manual cautions to make sure the plate voltage does 
not exceed 3700, and there are multiple primary taps. Maybe you 
can get away with it too.

Dave Hachadorian, K6LL
Yuma, AZ


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From: "Roger" <sub1 at rogerhalstead.com>
Sent: Sunday, February 07, 2010 12:59 PM
To: <amps at contesting.com>
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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