Vacuum Tube "grids"

There are hundreds, maybe thousands, of "specific references", some of which have been pointed out to you, but you don't like reading stuff from people who are smarter than you.

And I think it's very rude to get all snitty with the people whom you're asking for free help.

Good Luck! Rich

Everybody's been trying to tell you that they are NOT "functionally identical". They have very specific purposes. The control grid is generally the signal input. The screen grid reduces the interelectrode capacitance between the control grid and plate, to prevent parasitic oscillations. The suppressor grid is there to repel secondary emission from the plate, so that it doesn't fall back into the screen, wasting power and possibly degrading your signal.

You can do anything you want, but it's a good idea to learn some fundamentals so you have at least a shadow of an idea what you're trying to accomplish.

Good Luck! Rich

OOps! The screen grid is NEVER a "beam forming plate". The beam forming plates replace the suppressor grid.

Hope This Helps! Rich

(snip)

You should define what "work" means in your imaginings.

The problem is, you have heard from several people who DO have a point, but your point is wandering around pointless.

You can *force* each grid to (somewhat) function as a Control Grid by manipulating the applied voltage polarities and magnitude, but so what? If you wish to seek out the vagaries of tubes, put one in a test circuit. I imagine you could use a Screen Grid or a G2 as a Plate, too, but why bother unless it's just to see the effects. You will only see that if you build circuits and thoroughly test them with a variety of parameters.

"Tim Shoppa"

It is not too uncommon to use tetrodes or pentodes in "triode mode" by tying the grid and screen together.

In "triode mode" the screen grid is tied to the plate while the suppressor grid or beam plates are tied to the cathode as usual. The screen grid is crucial to the operation of a power tube - if tied to the cathode the tube will barely pass current, if tied to the plate you have a triode. If the screen supply voltage is insufficient, the tube will not pass full current and lack gain.

If the screen supply voltage is set too high, it will become the final destination for far too many electrons and quickly burn out from overheating.

That doesn't mean the screen grid is the same as the control grid, in fact in beam power tubes the screen grid is sometimes better identified as a "beam forming plate".

...... Phil

The bottom line is that are not functionally, mechanically, or electrically equivalent. They are similar. The control grid has the main emitted current control. The other grids are less effective, primarily because they have different spacings.

The screen grid is there to reduce effective interelectrode capacitance between the control grid and the plate.

The suppressor grid is used to reduce secondary electrons from the plate from hitting the cathode. Particularly in power tubes. Sometimes the suppressor is internally connected to the cathode and cannot be repurposed.

A touch of gedanken should tell you the results of your experiments in advance.

Be careful of using semi-remote cutoff and remote cutoff pentodes as triodes, you will get a very different result than you expect.

Just quit wasting all of our time crying about being told you are not doing anything that cannot be figured out from basic principles or searched for.

...

It's when the secondary emission electrons from the anode (plate) get back to the SCREEN grid that there are problems as it can cause negative resistance and a kink in the transfer response.

kevin