triode strapping a pentode submini. Grid 2 to plate? Or grid 2 and 3 to cathode?

[jackinthebox]

Hi Guys,

I have a question regarding triode strapping a submini tube. In this case a CV465.

I have seen a number of ways of connecting the extra grids and wondered if anyone has any thoughts on a preferred method and the advantages and disadvantages of the different methods.

The CV465 has the 3rd grid and the cathode connected internally so the 2nd suppressor grid is the only one which needs strapping.

Via a resistor to the plate/anode?

Or to the cathode along with grid 3?

Thanks in advance for any ideas.

 

[PRR]

> Thanks in advance for any ideas.

Put enough resistance in series with it so that you don't burn-up a valuable tube.

Use clip-lead to tie G2 to P or K.

You can also tie G2 to G1.

Nobody says you have to wire it to anything. Sometimes you see recommendations to tie-off all unused electrodes, but reasons are rarely given. And from knowing what goes on in there, I doubt letting G2 float will do any harm (though it may-or-may-not do what you want).

OR-- find the tube data. In this case it even specifies triode characteristics. They don't say how to wire it, but a comparison of Pentode and Triode mode voltages and currents gives an unmistakable clue.

FWIW: for "most" pentodes, cathode current is a strong function of G2 voltage and tends to zero when G2 is zero. So tying to K will probably just turn it off.

 

[CJ]

< so the 2nd suppressor grid is the only one which needs strapping... >

you mean screen grid,

 

[AndreasS]

I hope this helps

http://www.kaponk.com/~yanyong/ETF06TS.pdf

Andreas

 

[okgb]

It's a good question, I did something similar [ with a 5040 ? ] in the  " royer "  tube mic
have to dig out the article .

 

[radardoug]

Generally speaking in triode connection you want to strap the screen grid to the plate. The screen grid attracts electrons, and you have got them heading for the plate, so catch them by connecting to the plate.