BPM CR-4N sd mic low level , where to start trouble shoot ?

no audio just noise , I cleaned the pin beneath the capsule
and I'll open up the guts now.
It's an older double circuit board BPM  CR-4N mic and appears to be a single metal can xister  J7F9602 ?



Do we have a dead mic primer here ?
tia , any help appreciated .

step 1) Is the mic getting power?

The phantom makes it to the mic , I see 4v on one of the xister legs

How about the capsule?

Tried a different capsule, no change

seems a different circuit than the 4 transistor chinese schoeps  copy, with One transistor and a transformer
output

Trace the circuit.  I would guess it is a simple circuit
Compare it to other circuits
Maybe it is a km8X like circuit, or maybe it is something else

4VDC means little you need to measure a number of voltages pins of the jfet drain and source will be easy, center tap of the transformer or something like a pair of 2.2K resistor off of 2 and 3 for capsule and/or circuit power supply voltage
a jfet and transformer reads like no DC to DC converter for the capsule voltage
A picture would help

Should be an easy fix except if the transformer is bad

Thanks for loaning a hand Gus , here's some pix

I would start by checking continuity on the transformer windings.

Then replace the two tantalum caps. Especially the sand colored one, which is likely the one in front of the transformer.

It looks like some solder is missing on some of the PCB connections, 2nd and 4th pictures
4th and 5th look like a possible broken solder connections
I would check all the solder connections first
Then measure the drain and source voltages to ground

Looks like a possible 3pf feedback cap close to a 4pf like in the km84

When I have some time I might try to trace this from the pictures and compare this to a KM8X like circuit

thanks I'll dig in today and let you know,
I'll add that it hadn't been used for a while and then simply didn't work when it was next tried