Re: 4-1000A Screen Biasing...

["Grayson B Dietrich" <electrofire-at-juno-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Daniel,

A while back I had been doing research into building a VTTC with a 4-400A
of mine, and what was most often suggested to me was to wire the screen
and grid together and run the tube like a triode, rather than try to run
it as a true tetrode. I never did built that coil, but, I still have the
tube...   


Grayson Dietrich
http://www.electrophile.8m-dot-com


On Wed, 26 Jul 2000 17:22:23 -0600 "Tesla list" <tesla-at-pupman-dot-com>
writes:
> Original poster: "Daniel Boughton" <daniel_boughton-at-yahoo-dot-com> 
> 
> All:
> 
> I have two 4-1000A tetrodes which I am using for a
> VTC. Does anyone have experience biasing the screen
> relative to the plate? The 2000 ARRL handbook lists
> typical screen current to be 146 mA for class CT
> operation and 145 mA for class CP operation(not much
> difference) with a screen voltage of 500V and plate at
> 3KV. Does this imply that that the screen bias
> resistor will have to drop 2.5KV WRT GND and limit the
> current to 145mA? This would require a 362.5 Watt
> minimum resistor! This obviously doesn't make
> practical sense so something is wrong. What is the
> appropriate means to bias the screen?
> 
> Thanks,
> 
> Dan
> 
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