----- Original Message -----
From: measures <measures@vcnet.com>
To: <rakefet@rakefet.com>; Amps reflector <amps@contesting.com>
Sent: Tuesday, November 16, 1999 11:50 AM
Subject: Re: [AMPS] Simulating center tap
>
> >
> >I just noticed that the filament transformer I was planning to use (got it
> >free)
> >for my 2 x 3-500z amp does not have a center tap. It has two 5v 20a windings
> >which I was going to put in parallel.
> >
> Put the windings in series and you have a CT.
> cheers, Vic
>
Rich can type faster than I, Vic...good advice!
The way Eimac-Varian handled series filaments on their pair of 4-1000A
amps (yes, they used to be in the industrial amp business) is they wound
a third wire (#14) on the filament choke. This connects at the joint between
the filament pin of one tube and the other; where the RF comes in via a .01
cap from the exciter. The other end of the new third winding goes to your
newly created "center tap" where the B- connects. This balances everything
out. I like the series filament idea myself; if you develop a bad connection on
a tube pin or socket contacts, you get the "Christmas Tree Light" effect, and
both tubes go dark.
GL!
Phil, K5PC
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