Very Low 12AX7 current

[Leif_Bodnarchuk]

Using a 12AX7 triode as a split-load phase inverter, i was confused by the low voltage drops i was getting across the plate and cathode resistors. But playing through the amp, it sounds fine and dandy.

i'm using the same values as Fender: 56k on plate, and 1k & 56k on cathode.
Princeton schematic shows the cathode being around 50 volts above ground - i'm getting 4 volts (and that's with 240 at the plate.) Same 4-volt drop on plate resistor, giving me .07mA - not even a tenth of a milliamp.

But the thing sounds fine...

[soundguruman]

there are two voltages, and a regular meter can't read at least one of them, when you touch the probe to the circuit the voltage changes. welcome to the world of high impedance tube circuitry.
Break out your O scope and VTVM.
What you see is normal. You don't have the retro primitive equipment to measure it? Time to climb into the way back machine.

[Leif_Bodnarchuk]

Forgot to mention that in the power supply, there is a 330K resistor dropping the voltage to this valve.

That's a new one on me.

[Leif_Bodnarchuk]

i can now put this issue to rest... pilot error.

if you look at a princeton schematic, on the phase splitter, there is a 1meg resistor between the grid and a point where 56k and 1k cathode resistors meet. Without this resistor, the triode pulls very little current. in "my" design, the concertina splitter was getting grid reference, but now i see it was all wrong.

So sayeth the gods.

(and that 330k voltage drop resistor is now 1k)