[morzh]

Like I said, I do not think it is a short inside the tube. It looks strange but shorts drop voltage to much lower, closer to zero, values.

The dropout on the resistor might be OK. With the current up to 2.5mA it is allowed for a 50V to drop across that R4. The current is likely smaller.

But the drop at the R4 lower contact....the equivalent of that R14-15-16 bias source is 3.87K.
So 2.5mA would drop no more that 9.7V, which would add to that R4 drop. But it is probably not 2.5mA.

You know what, if it works normallty, maybe it is OK after all.

Let's see...say the SG current is 1mA. It will drop 26V with the tube inserted then altogetther, 22V across R4 and 3.87V after R14 (where it connects to R15).


So. Why did we decide this was a problem, again?