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Re: [Amps] filament supply options

To: kz1x@yahoo.com
Subject: Re: [Amps] filament supply options
From: ka1xo@juno.com
Date: Sun, 25 Apr 2004 22:56:42 GMT
List-post: <mailto:amps@contesting.com>
Dear Steve,

Does your intended amplifier use the filament to inject the input RF into the 
tube circuitry, or is one side of the filament perhaps tied to the cathode 
pin(s) on the tubes, with suitable bypass capacitance in various places?

Does your intended design use a set of bifilar-wound filament chokes with 
suitable bypass capacitance on the cold end(s)?

Does the design of your intended amplifier feed input R.F. to the center-tap of 
a possible filamant transformer?

In the above circumstances there are filament transformers with one side of the 
output tied to ground and other circumstances where the filament transformer is 
running with bothe sides isolated from ground and suitably bypassed.

If you were to substitute the switcher supply as a "black box" in place of a 
filament transformer is or are there any considerations relative to the above 
caveats that would cause you concern, (e.g., design considerations)?

Watts is watts, I agree. One of the criteria my work application dealt with 
when graduating from ferroresonant supplies to switcher supplies (other than 
the easily-swallowed cost savings) was the effect of a "complex" impedance on 
the operating radio bays, and if the power plants would be affected by all the 
RF. The final score has not been tallied yet. The MTBF for the Chinese (Delta) 
switcher supplies versus the MTBF for the older ferro's seems to be two orders 
of magnitude worse, and the Flat-Earth Society engineers all say "accumulated 
PLD's," while the D.C. True Believers counter with "R.F.hash."

Meanwhile, the Chinese are steadily sending replacements for the switcher 
modules....

Hal Mandel
KA1XO
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