[Amps] complicated Bias circuit

[Joe Subich, W4TV]

 > What is the point of having 24VDC from T2?

The bias supply is *negative* DC ... where do you expect to get it
other than a separate low voltage supply?

This bias supply is hardly complicated ... it is a scaled copy of the
circuit used in many other much bigger amplifiers/transmitters.

73,

    ... Joe, W4TV


On 5/4/2014 9:49 PM, Paul Decker wrote:
>
> FYI, if it helps any, this goes to a 3cx800A7 amplifier of some sort.
>
>
>
> ----- Original Message -----
> From: Paul Decker
> To: amps at contesting.com
> Sent: Mon, 05 May 2014 01:18:47 -0000 (UTC)
> Subject: complicated Bias circuit
>
>
> Hi builders.
>
> Hopefully you all can view this schematic.
>
> I'm trying to understand what T2 and associated circuitry do.  D17 and D18 seem like a simple bias circuit as SW3 selects between "class C" and "class AB1"  It seems opening R20 puts tube in standby (RX).
>
> What is the point of having 24VDC from T2?  Is it to have a smaller wattage D17 and D18?
>
>
> https://scontent-a.xx.fbcdn.net/hphotos-frc1/t1.0-9/10289874_10202768703951918_1823401065078063020_n.jpg
>
>
> Thanks in advance,
> Paul
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