[AMPS] Another Tube Max Plate Current Question

[Tom Rauch]

> This time about the 3CX800A7 Tube. What is the maximum allowable Plate
> Current of a 3CX800A7 Tube ?? Can it be operated at 600 ma without
> degradation or damage ??? 

Tubes do not live happily for many years at 500mA, and then 
suddenly die if you run 20% more current.

As a matter of fact, current has little if any effect on life as long as 
you don't exceed the peak emission current of a MOX cathode tube.

With thoriated tungsten, like an 813, you can hammer the heck out 
of the emission with no ill effects at all.

3CX800's actually have a published IVS (intermittent voice service) 
rating that exceeds the value in the typical operation tube tables. I 
don't have that data handy, but you would certainly be fine at 20% 
over normal ratings as long as you don't exceed the dissipation 
rating of any elements and have the rated filament voltage applied.

Excessively low heater voltage is the real enemy of MOX cathode 
tubes being operated at the max.
73, Tom W8JI
W8JI@contesting.com 

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