Gefell MV 691 - Low Output

[smilan]

Hi,
I have a Gefell MV 691 with a M71 capsule.
The output of the 691 is significantly lower compared to a MV692 with the same capsule.
I'm suspecting that the DC to DC booster is not supplying enough voltage to the capsule, I measured the voltage between the junction of R10 with C9 and R9 with C8 and it is 41V
The voltage across D1 and D2 is +\- 37V.
So it seems to be too low, isn't it?
I measured the inductance between the coil leads to the ground bus, so BV137 seems to be good.
What else I should test to find the problem with this mic?

 

[Murdock]

I think sometimes the screw wich holds the core halves of the coil together comes a bit loose and therefore reduces inductance. Worth a try to tighten it a bit maybe. But don't overdo it.

 

[smilan]

I think sometimes the screw wich holds the core halves of the coil together comes a bit loose and therefore reduces inductance. Worth a try to tighten it a bit maybe. But don't overdo it.

Yes, after spending hours trying to find what's wrong with the 691I found the solution for the low output, I was needed to screw the capsule harder than I usually do and the output came back to normal