How to determine grid leak current?

[arnoldc]

I've been looking at the tube manuals and these does not seem to be part of the specs. Some mention grid leak resistor values.

I ask because I'm going to have grid chokes made for my 50 amp.

I currently use 5,000H 1mA grid choke on my 45 amp and it is ok for many months now. I'm not sure if it will work for the 50 hence I'm looking for this data. I don't want to make the 50 a light bulb and fry it.

Thanks!

 

[audiousername]

You probably will be fine as long as the DCR of the grid choke is less than the maximum grid circuit resistance for the 50 (10kW, IIRC)

 

[arnoldc]

Hi Jason,

thank you very much for your input. A friend is giving me a 5,000H 5mA grid choke and I'll figure out measuring the DCR when I get it.

I still wonder though, how come this spec is not in tube manuals, seems to me as not that critical huh?

 

[audiousername]

thank you very much for your input. A friend is giving me a 5,000H 5mA grid choke and I'll figure out measuring the DCR when I get it.

You're welcome

It seems you have a lot of nice friends, too

I still wonder though, how come this spec is not in tube manuals, seems to me as not that critical huh?

I assume it is because the grid current (although small when Vg1 is negative) changes with a whole host of things, and probably would vary with valve age as well since some emissive cathode material may very well sputter on the grid over its lifetime.

 

[arnoldc]

It seems you have a lot of nice friends, too

I have another friend who has thousands of tubes and everytime I ask him how much, he always say "just get a pair." I never asked for his Western Electric stash :lol:

Thank you for an enlightening discussion on grid leak current

Cheers!