Dick says:
>Don't you think the HV filter will generally discharge much faster than
>the cathode will cool down & lose emissivity, Peter...?
It's all going to depend, isn't it? The relative time constants of screen
and bias supplies, the time constant of the HV supply..........you could get
the case where the tube is cut off and cooling and then the bias supply
falls before the HV has. It's a bit academic, though - the probability of it
giving a problem is pretty remote. If you're running multiple amps and
switching the heaters as you change band, leaving the other voltages on,
it's possible. X ray tubes have back bombardment which heats the cathode, I
believe, but I don't think anyone on this reflector is running B+ voltages
up in 100kV region - not in amateur service, anyhow.
73
Peter G3RZP
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