Unusually high cathode voltage in single ended plexi

[isaac_teller]

Hello. I mated a plexi preamp to a 6V6 single ended output. I don't know why but I'm getting 41 volts on the cathode of the 6V6 with a 6V6 plate voltage of 300 volts. What gives? The preamp is everything up to the 0.022 cap before the phase inverter.

[isaac_teller]

My bad. This is the schematic.

[tubeswell]

My bad. This is the schematic.

Still can't see the 6V6 which is supposedly the problem :-)


Have you double-checked (metered) the R-value of the 6V6s cathode resistor?

[isaac_teller]

This is just the schematic of the preamp. The 6V6 comes right after the last 0.022 cap before the phase inverter. The cathode resistor of the 6V6 is 470 Ohms with a 50 mf bypass cap.

[shooter]

my math says that's ~~~ 14W a tube, pretty close to normal, what's it sound like?


EDIT:  I assumed 2 6V6's
If only one you have a problem 

[sluckey]

This is just the schematic of the preamp. The 6V6 comes right after the last 0.022 cap before the phase inverter. The cathode resistor of the 6V6 is 470 Ohms with a 50 mf bypass cap.

Still unclear exactly how the 6V6 is connected to that cap. Surely you don't have the PI tube and circuitry? Surely you have a resistor from 6V6 pin 5 to ground? The voltage on pin 5 should be zero.

[isaac_teller]

The 6V6 connects to the preamp similar to how the EL84 connects to the preamp here. Turns out that I forgot to put a 220K resistor from pin 5 to ground, like you said.


https://www.tube-town.net/cms/userfiles/downloads/jim-schem_layout.pdf