Odd 5f6A voltage question

[jlatrace]

I deceided to make a blue print of the voltages in my 5f6a clone and compare them to the original Fender schematic. In doing so I noticed that all voltages (power and pre-amp) were on spec (within 1/4% of the schematic) except in the phase inverter. After the 1 meg resistors the voltgages read 13 & 14 vdc instead of 22 & 23 vdc. Before I resort to trial & error I thought I'd ask does this strike anyone as odd and what could cause this variance, tubes, 1 meg resistor tolerances or other condition?

[tubeswell]

After the 1 meg resistors the voltgages read 13 & 14 vdc instead of 22 & 23 vdc. Before I resort to trial & error I thought I'd ask does this strike anyone as odd and what could cause this variance, tubes, 1 meg resistor tolerances or other condition?

wrong value tail resistor?

[loudthud]

You can't directly measure the voltage at the grids of the PI tube. Your meter's 10Meg input impedance pulls the grid towards ground as it forms a voltage divider with the 1Meg grid leak resistor. This changes the bias on the tube and it couducts less. Measure the voltage at the junction of the 1Megs and the tail resistor. The voltage across the 1Meg resistors will be only a few millivolts.

[jlatrace]

Thank you. That is exactly the information I was looking for.