Another approach is provided in the RCA Transmitting Tube manual page 66.
"When ac voltage is applied to a filamentary cathode, dc circuit returns
should be made to the mid-point of the filament
or filament-supply circuit to minimize hum. A convenient point for these
returns is a center tap on the supply winding
of the filament transformer or the junction of two equal resistors connected
in series across the filament circuit".
The manual contains the schematic of a triode amplifer which uses this
approach on page 297. In this diagram, a type
8000 triode is employed and its filament is supplied ac from a non-center
tapped transformer. A 50 ohm center tapped
wire wound resistor is connected across the filament circuit, and the center
tap is connected to ground. The schematic
also provides bypass capacitors across both halfs of the resistor to ground
(0..002 uuf).
The filament requirments for the 8000 are 10 volts at 4.5 amperes. (The
nominal plate voltage is 2500 v at 300 ma in this
particular schematic.)
Regards
Ed
----- Original Message -----
From: "Bruce Plantin" <plantin@tcomlp.com>
To: <amps@contesting.com>
Sent: Tuesday, February 27, 2001 2:55 PM
Subject: [AMPS] Filament Xfmr
>
> Hi all,
> Is it possible to use non-center tapped filament xfmr with a
thoriated-tungstun filament RF amplifier tube? Thanks in advance.
>
> Bruce W3BP
>
>
> --
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>
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