Finally got around to it and measured the plate to cathode capacitance.
I was quite surprised. It was as high as stated in specs. I got about 20pF but
that includes
a few pF from setup wiring.
I thought I'd try another tube that has similar dissipation and
characteristics 304TL.
Its plate to cathode capacitance was less than a pF.
So even grounded grid operation with a 833A may not be stable with out some
neutralization.
Used spectrum analyzer and tracking generator. Measured feed thru signal level
and calculated capacitance based on
frequency and input Z of spectrum analyzer. The grid was grounded and signal
fed to plate and cathode connected to
spectrum analyzer.
73
Bill wa4lav
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