Henry radio runs the filaments in their amplifiers with the filaments in
series. There is no center tap on their filament transformers.
They use a small choke hooked to the "center" of the 2 tubes. They insert
the drive power from the tuned input circuit at this same point. The choke
is for rf isolation. Works great!
Good luck and 73!
Jim W7RY
-----Original Message-----
From: Roy Koeppe <royanjoy@ncn.net>
To: Amps Reflector <amps@contesting.com>
To: <amps@contesting.com>
Date: Sunday, October 03, 1999 1:47 AM
Subject: [AMPS] Re: Filament Xfmr.
>
>About:
>
>"I am building an amp with four 3-500Z using low bands only (160 and
>80m).
>I do have two filament transformers, 5V/80A w/o a center tap on the
>secondary coil. The other one contains four coils with 5V/25A ea. coil
>also
>w/o any center taps on the secondary side." (Etc.)
>
>How about connecting a small "audio" or "power supply" choke from each
>side of the secondary to "eventual" ground? Calculate the inductance
>value of them so that they will only allow a negligible (AC) current
>flow to ground while maintaining a balanced condition for all voltages
>involved in the circuits. I think reasonable sized, cheap chokes may be
>possible but must have low DC resistances. Maybe from junk box.
>
>73, Roy K6XK
>
>
>
>
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampsfaq.html
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>
>
--
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