How to connect a pentode in tetrode mode?

[aldovan]

Friends

I need to connect a pentode in tetrode mode.
How do I do that ?
Do I connect the G3 to the plate?

Thanks

Aldovan 😀

 

[DF96]

Yes, I think so. Be aware that g3 is not designed to take much current so could overheat.

 

[ballpencil]

How about leaving G3 floating?

 

[waltube]

which tube is?
Normally the g3 is connected with cathode, pin 1 and pin 8

Walter

 

[artosalo]

What is the application that requires tetrode connected pentode ?

 

[DF96]

Leaving g3 floating means that it will adopt whatever potential it likes. If it catches electrons then it will go negative until it finally repels them sufficiently to not catch any more - you might as well connect it to the cathode. If it loses electrons due to secondary emission then it will go more positive and lose even more. In either case you have lost control, so don't leave it floating.

 

[hpeter]

What is the application that requires tetrode connected pentode ?

Good question, but unless its a dynatron AM radio; it does not need real tetrode.
Quite hard to buy those anyway; everything today is beam t.

 

[211hojbjerg]

Hi,
Connect G2 and G3, l tried that with e180f and ef184.

Best regards
Karsten

 

[Hyperman75]

Hi

I don't understand the question because a pentode is a tetrode with a third grid (G3), connected to the cathode, internally or externally.

So if there is no internal connection, you have do do it outside : G3 to cathode...

Jacques

 

[dady]

Hi, if they are power tubes, tetrodes have two plates in the sides of the principal beam or flux of electrons, this plates are Absorb the electrons that have bounced off the anode. They are returned to the cathode, in the case of power pentodes the function of G3 is the same, the grids absorb. EL34 y is a pentode with G3 that we have to connect externally to the cathode terminal. In this case we have the option in see what happen with the behavior of the valve.
I don't know signal tetrodes.

 

[glennb]

Friends
I need to connect a pentode in tetrode mode.
How do I do that ?
Do I connect the G3 to the plate?
Thanks
Aldovan 😀

What type of pentode tube? There are actually not many pentodes that have a separate pin out for G3.
You could connect G3 to A through a resistor such as 10K. You will find the G3 current will very low, eg. 1uA.
Connecting G3 to K is a normal pentode connection, so it can't really be called tetrode mode.

 

[JMFahey]

Why not connect G3 to Screen through, as suggested above, a 10k resistor?

Connecting it to cathode is normal pentode use, to anode it may well negate what screen is doing because it will follow whatever anode does; to screen means it will basically have same voltage and follow what it does, best way to make it "transparent/it´s-not-there", call it a "sub-screen" if you wish.