Will
Actually its not an RF application. The 3-400Z is a driver for a
4CX3000A, which screen modulates a pair of parallel 4CW250,000B
tetrodes. These are in turn the plate modulators for a Burle 7835 3
MW pulsed triode at 200 MHz. So the glass tube is the first stage
after a transistor, in the pulse modulator. It is actually used as an
inverter, so that the gating pulse is low, there is plate current,
and when the pulse is on, the 3-400Z is biased into cutoff. It is
less complex a circuit than I described, there is even a big fat
coupling capacitor on the output of the 3-400. I don't expect to have
much difficulty in making a 3-500Z work in the socket, once I get the
taller glass chimney. I may have to tweak the drive to the tube so
that it is truly cutoff when I am pulsing and drawing current when i
am not.
This four tube modulator is about the size of a small bathroom, on
wheels. Output is 21 kV DC at 220 Amperes, for millisecond long
pulses. The DC power supply feeding the top of the 4CW250,000Bs
(plates) is about 29 kV DC, 200 uF of capacitance.
73
John
K5PRO
>
>John,
>Asside from the physical size of the innards, I always thought the
>3-400z had the same base as the 3-500z? If so, about the only thing
>will change is the increased pate current if you run them at their
>higher output and that will change the plate impedance so a tweaking
>of the tank coil may be necessary. If your going to run them at the
>same power out as the 400's then nothing should change
>theoretically. You would most likely have to cut the drive back some
>though to achieve this. If I'm off here let me know and will be glad
>to help you on converting it.
>
>Best,
>
>Will
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