[Amps] Cathode Choke

[Jim]

Is this a B&W or Viewstar PT3500? Is so, W8JI was not the designer.


Thanks
73
Jim W7RY

On 10/3/2019 2:47 PM, Roger Parsons via Amps 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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