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[Amps] Mil-Spec Fil Xfmr performance

Subject: [Amps] Mil-Spec Fil Xfmr performance
From: "Pat Barthelow" <>
Date: Fri, 31 Aug 2007 11:39:54 -0700
List-post: <>

I am parting out a robust, home brew RF Deck that carried a pair of 4-400 A 
tubes, very similar to a  3-500Z design.  It was robustly built, and has a 
huge silver Pi Net rotary Coil, Vac Variable Tune and Load,
heavy TX/ RX  relay,  8 big sprague feed throughs,  and a Mil Spec Filament 

My question is about the Fil transformer, an old school completely sealed 
metal case unit.  Inscribed on the case are designators:
Grade 1 Class A Audio Device Company  A8023  5252C  117V
Output has two ea  2.5V center tapped windings which are seriesed together, 
with the middle terminal of the two in series,  grounded, and the 5 volts 
picked off the ends of the grounded, centertapped, serised  windings.

The Current spec printed on the transformer case shows 23 Amp capacity 
secondaries.  A pair of 3-500Zs needs 30 amps to function.  The amp worked 
fine for decades, and I believe I actually measured 5.0. volts at the tube 
pins in operation, a long time ago.
With a 23 amp design current capacity, how is it possible that the 
transformer held up to 5.0 volts, with a 30 amp draw?

Are the Mil type transformers conservatively rated?   Is this over loaded 
transformer likely to "let the smoke out" some day?   Perhaps, it can  just 
tolerate the losses of  higher current draw, and the terminal voltage is 
higher, because the applied line voltage is 125, instead of the 117 design 
voltage.  I never checked if the transformer case was extra hot, in 

All the Best, 73,
Pat Barthelow
Jamesburg Earth Station  Moon Bounce Team

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