Strange G7!

[pbirk]

I have recently built a G7. It is hum free and sounds very good, but in a totally wrong way:
In omni position the audio signal is very weak, but when I tap the microphone it is very much alive.
In cardioid it works, but the backside is the active one!
In fig-8 the signal gets stronger and it is kind of fiig-eightish, but the back side is the dominant side.
The PSU gives perfect values.
The variable patterns to the back should read 0-80-160 volts in omni, cardioid and fig-8, but the values I get is 0-15-30 volts measured between back and front. Center seems to be dead with none or very small values.

If anybody out there could help me I would lose ten tons of wight. This is so frustrating!

pbirk

 

[Sredna]

Sounds like you wired the capsule the wrong way, which capsule did you use?

You can't measure the polarisation voltage (with a normal DMM) on the capsule, too high impedance.
Measure before the 1G resistor.

 

[pbirk]

The capsule is absolutely not wired the wrong way. I have checked again and again.
Yet I have to confess:  I did totally goof in the building process: on the pattern switch on the PSU I soldered the output to the cardioid point, the cardioid to the output and did the same with the fig-eight and omni! Late night job....
So I guess some components are damaged?
The capsule now is an MK-67 french manufactured U-67 replacement capsule. When, and IF, I get this mike right, the capsule will be a Neumann M7 capsule.
pbirk

 

[Sredna]

on the pattern switch on the PSU I soldered the output to the cardioid point, the cardioid to the output and did the same with the fig-eight and omni! Late night job....

Hmmm, Im not shure I understand this sentence but connecting (soldering) the "Pol." point  to the cardioid poit shouldn't hurt anything.

Try measuring the voltages (regarding to ground) before the resistors. Ie for the backplate (middle) you measure between ground and the junction between the 1G resistor and the two 470k ones.

For the rear membrane you use the point between the 100n cap and the 33M resistor.