[Amps] neg screen I in tetrodes-- TSPA

[Steve Thompson]

> 3) The screen material and coatings is different in the 4CX- designs,
> and causes more secondaries when struck by primaries from the main
> beam.
As a gross generalisation, I reckon that well used 4CX250s have higher reverse 
screen current and more flashover problems. I can imagine that tiny amounts 
of cathode material might disperse over time and contribute to the effect - 
does the same happen with the filament coating on directly heated tubes?

Steve