On Thursday, March 2, 2017 at 2:35:02 PM UTC-5, wrote:
" ** Like hell I did.

Try reading it AGAIN !!!

IF you double the voltage into double the load, the CURRENT stays the same.

But double the voltage at the same current is TWICE the power.

Power = V x I "

Fine, but I don't know why you expressed it that way. There is still a limit to how much voltage you can have. Generally, output tubes are not in series, they are in parallel. As such the impedance into which they work (determined by the transformer of course)must be decreased to realize any increase in power output.

"** Any data sheet will quote max screen dissipation - usually only a few watts.

The fine steel wire will glow red or even white if the rating is exceeded..

Then guess what happens ?? "

It becomes a triode ? LOL. Not really because the suppressor grid is still in the way.

"If the screen supply voltage is too high, it take excessive current whenever the plate voltage swings low under load. "

This is one of the things I have trouble grasping when it comes to tube technology. I am younger than you and tubes existed only at the beginning of my career. I adapted to solid state quickly and made a profit...

I wonder some things, like when the plate voltage goes lower than the screen voltage. Are you saying that the current flows from the screen grid to the plate ? Or is it pulling from the cathode ? I'd guess cathode but that is just a guess.

There are a few other things about tubes of which I lack knowledge, but I am only 56 and this is 2017. Like the suppresor grid, how the hell did they even find out they needed that ? I mean, some guys in white lab coats looking at a (probably Tektronix) scope saying "There are electrons bouncing back from the plate, we can improve this tetrode by adding another grid". How the hell did they figure that out ?

I think a lot of refinements are trial and error, or just plain dumb luck. Maybe some hack was assembling the plate structure and left some support wires in place instead of cutting them before stuffing the assy in the bottle and sealing the glass. Make connections to the wrong wires and..

It's the guys like Tesla who could envision things like polyphase AC before anyone else that impress the beejeezus out of me. Edison was a trial and error guy while Tesla was reading blueprints from inside his skull.