Check with W8JI...I believe that he is the designer.
N8DE
Sent from my Verizon Motorola Smartphone
On Oct 3, 2019 3:47 PM, Roger Parsons via Amps <amps@contesting.com> wrote:
>
> I am attempting to repair a PT3000 amplifier for a friend. (This is a
> prototype of a design that never went into production.) The amp uses an 8877
> in grounded grid.
> I am puzzled about the cathode choke, as the cathode and heater are connected
> together for RF, all three connections go through the choke, and the heater
> is fed from DC. This has the undesirable effect that because of the voltage
> drop in the choke something over 6V is necessary to give the proper heater
> voltage. And the DC supply has broken and I want to replace it with a
> transformer....
>
> I can't see any advantage in doing things this way, but I may be missing
> something. FWIW some other amps I have worked on have kept heater and cathode
> separate and have worked fine (MLA2500 as original, and as modified by me to
> use a 3CX800, an ex CBC 1kW FM broadcast transmitter (8877), and as modified
> by me to be an HF Class AB1 amp.) I'm sure that other examples can be found
> for both techniques.
> Is there a good reason?
> Thanks
> RogerVE3ZI
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