Re: Pentode amp experiment.
Hello,
With g3 connected to the anode you are running the valve as a tetrode rather than a pentode, although with g2 connected to the cathode it will act as a suppressor grid as well as a screen grid.
As Chris has said the anode current of an EL34 at zero bias and Va =250V, is over 250mA, however by connecting g2 to 0v you are probably reducing this to well below 25mA.
By connecting g1 to the cathode with a 3.9meg resistor you have a grid leak detector, although 3.9 meg is a higher than the normal 1meg to 2meg for a grid leak, you might well be getting AF as well as any residual RF at the output.
Yours, Richard
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