Hi Jaime,
Wow, you are quick – congrats to your new frequency generator.
Here an overview of your measurements in the order of the signal path:
Stage Input Output Ampl.-Factor comment
V1a 0,051 2,04 40,0 ok
Blast
0,041
Input value is missing
V1b 0,07 1,51 21,6 seems too low, try a different preamp tube and measure V1a and b again
V2a 0,074 0,8 10,8 both inputs and outputs are supposed to be roughly equal
V2b 0,011 0,7 63,6 but aren't
If your measurements are correct, there is something wrong in your PI.
The principle of this kind of Pi is, that the first tube amplifies the signal and inverts the signal and feeds the first power tube.
The second PI-tube-half must deliver a signal of the same amplitude in the opposite phase. Therefore the signal of the first tube is tapped, a voltage divider attenuates the tapped output of the first half and feeds it into the input of the second tube half.
The second half amplifies and inverts this signal and the output goes to the second power tube.
In your case the output of both halves is drastically different. I assume, Dirk’s published circuit is correct and tested, so there must be errors in your build.
Please check all the component values around your PI.
The amplification factor of V1b seems very low too. Please check the component values too.
