Sorry... Meant to say PT3000 amplifier.
Fern, VE7GZ has or had a couple of the Viewstar (which is as I remember,
the only company that built them, in very limited quantities).
I believe Fern has all the numbers and is really well versed in them.
Comes down to filament choke or no filament choke on an 8877. I have
build and run them both ways. They work fine either way.
Lots of school of thought on choke VS no choke.
If you search the amps archives, you will find HUNDREDS of emails about
this very subject.
Enjoy your reading.
Thanks
73
Jim W7RY
On 10/4/2019 4:33 PM, Jim wrote:
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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