From: Robert Groh <rgroh@swbell.net>
To: amps@contesting.com
Subject: [Amps] Question about 4-1000A operation
Date: Sat, 14 Jul 2007 22:43:17 -0700 (PDT)
Well, I've got a bit of a problem and would like some opinions. Another ham
tried out one of my 4-000A tubes and reports the following:
Filament fine, tube lights up fine
e ran it with filament only for 4 hours and then applied 1500V to the plate
Result: no grid current:
Could you mean plate current? As someone else mentioned, I think yoiu
would not expect grid current without drive.
Another 4-1000A tube was tried in same circuit and gave 50 mA idling
current.
Hmmm... Plate Idling current?
4-1000A Schematic, shows Pins 2 and 4 connected to the control grid, Pin 5
to screen grid.
Perhaps the tube has an open circuit between one of the control grid pins
and the cotrol grid, and yet still "work" depending on how and which of
those pins were used.
Did you check for continuity between Pins 2 and 4, and for open circuit
between Pins 2 and 5 and 4 and 5?
I'm not sure what exact circuit he is using - probably grounded grid. No
idea of what screen voltage.
So it seems that my tube is no good. Any other possibilities we should try
before converting it into table lamp?
73Bob, WA2CKY
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