In pulsed operation, here is an example of actual operation where
screen current goes up, when anode is dropping off:
A 18 kV anode B+ supply has an interlock relay powered off a voltage
divider, so that the screen is only powered after approx 12 kV on the
anode. When it is misadjusted (the divider had a pot), could be even
lower. Separate screen power supply had its own caps, etc.
I could watch the screen current soar (used a current transformer or
shunt and scope) when that interlock was set low (anode = 6 to 8 kV
ferinstance) but only for a short time, like the time it took relays
to open, etc.
Doesn't seem to hurt the tetrode with short spikes of high screen
current, it is the long term average screen dissipation which kills
it.
73
K5PRO
john
>
> >> >> >Also if one were to turn off the HV supply and key the rig
>before the HV
>>> >> >decayed to zero, you could have low plate voltage but still have full
>>> screen
> >> >> >voltage. That would mean very high screen current.
>
> >> >> >Gary K4FMX
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