> ?I would not run the tube at their stated? zero bias....... idle current is way too high.? It needs bias.? ? 50 ma? for idle current is ample.

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I agree with you. That's why with a 2500 V HT I chose a -9 V bias which brings the quiescent current to 2 x 50 mA.

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The curves I posted are with the original Drake L-7 schematic where the grids are not actually grounded. The difficulty is being able to easily return to the original assembly, if the ground-grid wiring was, for example, unstable.

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I am currently making a wiring modification to ground the grids.

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I kept the possibility of setting the polarization to zero so as to make the plates redden periodically, on the simple rest current, to perfect the degassing of the tubes