Re: 4-1000A Screen Biasing...

[FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 7/26/00 8:34:51 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

> > 
>  > 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?

Dan,

You may be able to connect the screen and control grids together
and run the tube as a triode.  I've never tried it with that particular
type of tube though, and some folks have had trouble with screen
grids burning up in that configuration I hear.

Cheers,
John Freau