[Amps] Fil transformer
jim.thom at telus.net
Sun Aug 13 12:51:35 EDT 2017
Date: Fri, 11 Aug 2017 19:58:58 -0400
From: "Carl" <km1h at jeremy.qozzy.com>
To: "Jim Thomson" <jim.thom at telus.net>, <amps at contesting.com>
Subject: Re: [Amps] Fil transformer
----- Original Message -----
From: "Jim Thomson" <jim.thom at telus.net>
To: <amps at contesting.com>
Sent: Friday, August 11, 2017 1:01 AM
Subject: [Amps] Fil transformer
> Date: Thu, 10 Aug 2017 07:08:54 -1000
> From: Merv Schweigert <k9fd at flex.com>
> To: amps at contesting.com
> Subject: Re: [Amps] Fil transformer
> <How about the old time trick of putting two low value resistors to
> <ground, one from each side of the
> <filament, used to be used for a center tap many times in days of old.
> ## This isnt 1956 anymore. The B- has to float above ground a bit on a
> gg triode amp, in
> order to measure both dc plate + dc grid current.
> The two resistors would have to be wired in series....across the sec of
> the oem fil xfmr.
> The junction point of the resistors becomes your new CT.
** What does 1956 have to do do with anything? The 2 resistors in series
between the filament and the mid point becomes a virtual CT. I mentioned
## The fellow was talking about wiring each resistor.... from each end of the
fil winding... to chassis. That puts the chassis as the virtual CT. Which will work,
except now you cant measure dc grid.... nor dc plate current.
## two resistors in series, across the entire fil sec winding...with their junction point
as the CT as you stated, is the only config that will work, plus allow for normal plate and
grid current metering.
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