Some years ago I measured some valves, including 3CX800. I don't
think I have kept the results but the general result was that the
C was about twice the data sheet value, and wasn't changed by the
mechanical setup unless the metalwork was really close - much
closer than you would want when looking at a layout.
Steve
As I do not (yet) own a decent LCR meter does anyone have a decent ball park
figure for the stray C to chassis for a 3CX800A7? The side walls are 1.25
inches away from the tube and the lid is 2.5 inches above.
Also thanks for all the help with my previous questions. I should mention that
this is a retrofit to an existing 2m amp and C1 is 6pF maximum and I would like
to use this part if at all possible.
I have a design that works on paper for strays C of 4pF with a Q of 8 using an
L-Pi-L configuration as recommended by a few of you. The 4pF stray value does
not seem unreasonable but it is a guess. I am sure that someone must have
measured this.
Regards
Conrad PA5Y
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