[Amps] Grid fuses (was: Life and gain of 3-500Z)

[R L Measures]

On Jul 21, 2006, at 4:21 AM, Tom W8JI wrote:

>>> An 8877 cathode can emit 50A.  If 50A is flowing into the
>>> grid, how
>>> does your electronic circuitry stop it?...
>
> That sounds factual on the surface but the 50 amps actually
> comes from anode current at 10kV anode voltage in pulsed
> applications with a 3CPX1500A7 pulse rated tube with hotter
> cathode and driven with a kilowatt, not 8877 grid current.

The tech spec sheets tell us the 8877 cathode can emit >50A.  If the  
anode happens to be no more positive than the grid would many  
electrons go to the anode?
>
> Very few amplifiers would be running the cathode at 3CPX1500
> temperatures and even fewer would have 10kV dc between the
> cathode and other elements.

The problem is what happens when the anode potential of an 8877 drops  
to under 100v.
>
> 73 Tom
>
>
>

R L MEASURES, AG6K. 805-386-3734
r at somis.org