[OZ4]

My armchair calculations.

As for the DC bias on the #24 detector:

(Many times the cathode is grounded. With the grid being driven - v. )
In this case bias is set up by the fact the cathode is raised up off of chassis ground through the resistor #12 causing is to become +v in relation to grid which is grounded through the IF winding.

So measuring from ground to the grid will not give proper a bias reading. 

The bias is determined by the DC current through the tube cathode resistor which is the same at the plate circuit.

It would be helpful if they had listed the plate current for the detector. 

Calculating the bias voltage via current.
So the plate supply voltage comes to point J via the choke #30.
I guess this voltage is approx 150 volts At J. (Measure this and recalculate as below.)
( This is from chassis ground. The chart voltages don't mention the reference point. Measuring from point B would increase this by
 the negative offset of the 187 ohms at #2 and #3. )


From the chart the voltage at the plate is stated to be 35v.
(I am sure this is lower than would be measured with today's voltmeters.)
that means the rest of the approx 150v source is dropped across the plate resistors #17,#18.
And 150-35=115v drop. And assuming they are good values the current through the loop should be approx .19MA. That's less than 1 MA.


So with bias determined by the DC current through the cathode resistor. Now with .19MA x 50,000 ohms we have 9.5volts. And that should be -9.5v.


Apparently the actual plate voltage is not critical so all this is pretty fuzzy.


This seems like very little current compared to the other tubes. But as this is being used as the detector I don't think it needs much.