NC20F is specified for 75H/25ma. For tubes such as 01a or 76 which has less than 10ma plate current but high plate resistance around 10k (or slightly more), will NC20F be adequate?
Is there a quick way to roughly estimate primary inductance with, say, 5ma as opposed to 25ma DC going through primary?
Is there a quick way to roughly estimate primary inductance with, say, 5ma as opposed to 25ma DC going through primary?
It should be OK, NC-20 can work with source impedance of 5-10 K. At 5 mA, the primary inductance will be much higher than rated; I would expect at least 150 H. The exact inductance is impossible to calculate but dependence of inductance on standing DC current is approximately hyperbolic. Inductance at specified DC current can be easily measured.
