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[Amps] screen grid current dropping

To: <Amps@contesting.com>
Subject: [Amps] screen grid current dropping
From: "ka1mwp" <ka1mwp@comcast.net>
Date: Thu, 11 Jun 2009 18:33:29 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Well, here is one I can't seem to figure out easily..
 
My GU-84b amp with 2100v plate, -65 on control grid, 365v on screen
grid, have a meter monitoring the
Screen current.
 
I watch this current go from .7ma idle to 25ma at 1kw key down..(can't
do this long on the oil filled dummy load)
 
The current drops from 20 or so ma down thru 12 with the voltages and
output watts staying pretty close to values.
 
I'm using the tetrode boards and have it setup as in the manual..only
slight component value changes for the screen
Resistors to get correct volts out, which is rock solid at 365vdc.
 
Clues to look at?
 
The schematic I posted on the site is pretty close to what I have.
 
 
http://home.comcast.net/~ka1mwp/gu84b_new_sch_rev4.JPG
 
 
thanks for any help in the search.
 
Chuck
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