Re: Really big VTTCs

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Shad <shenderson@xxxxxxxxxxxxxxxx>

Hi All,

It's very important to keep in mind that if you triode connect a pentode
(tie the screen to the plate), the maximum voltage of the *SCREEN*
becomes the maximum plate voltage.  You'd be better off building a
dedicated screen supply (or using a dropping resistor) to supply power
to the screen.  Sure, it'll burn off power, and complicate things a
*little* bit, but it's much better than really limiting the plate
voltages you can run.

Also, don't exceed the dissipation rating of the screen.  They have a
specific job to do, but they lack the anode's ability to shed heat
efficiently.

Tetrodes are the same way.  When the second grid is connected to the
plate, the maximum plate voltage drops.  It's much easier just to use a
suitable dropping resistor to feed the extra element.

Just figure the voltage drop and current necessary for the screen and
then calculate the appropriate resistor for it.

Hope it helps!

Shad H.



> I've read that the tetrodes are a little less convenient, but still
> usable by connecting the grids:
>