I don't have a schematic but I have two v69ms. I started to trace them but only did a small section.
I will look for my notes.
IIRC
Both halfs of a 12ax(t)7 in parallel, 200VDC B+, 56pf cap anode to grid. Cathode biased, a plate resistor, Plate out. Capsule direct to grid. This is a gain of -1 tube section.
Check the neumann PDF "Microphones" at the neumann site look at the km84 and fet47 type fragments
The next section looks something like the parts for a Schoeps circuit a 170 fet and two PNP transistors with a module covered in epoxy.
9VDC for the filiments but with a series resistor inside the microphone to drop the voltage down AND limit the turn on current for the heaters