>Been out a couple of days.
>
>Spectrum analysers - can lie worse than a Personnel manager, even more so
>with a FET probe.
>
>Thoriated filaments. Rich is quite right about the carburization business -
>it's described in old editions of Terman. However, leading on from that, the
>maximum emission when saturated from a 3-500Z filament (or any of the 5volt,
>14.5Amp thoriated filaments is of the order of 60 to 70mA/watt. That means
>a maximum tube current, in saturation, as opposed to arc current, of around
>4 to 5 amps dc. If that is going to bend filaments, why is there no warning
>about running the filaments on dc? And will the grid bend at 5 amps? Maybe
>someone can calculate the bending force. If that current is the result of a
>parasitic, where does the plate get its current from?
>
>This is why I have a problem with the parasitic theory.
>
? Who can say what the maximum peak cathode current is when a cloud of
electrons has built up around a 3-500Z cathode, prior to a one-shot event? .
. The next time you discover a filament-grid shorted 3-500Z, Peter, it might
be interesting to measure the resistance of the VHF suppressor resistor, Rs.
cheers
Rich...
R. L. Measures, 805-386-3734, AG6K
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