John,
I didn't think it would be much of a change but is the sockets different
between the two, I always thought they were the same? That's what has me
thrown, why would you need to change the sockets?
Best,
Will
*********** REPLY SEPARATOR ***********
On 10/1/05 at 5:19 PM John T. M. Lyles wrote:
>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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