Sennheiser MKH40, different schematics?

I am repairing a Sennheiser MKH40, I thought I had the schematic, but the one I have here is completely different!  :
This one doen't have the traditional BC transistors on the PCB, but three 2SK30 FETs near the capsule!
I suppose two FETs are buffering the signal(s) from the capsule and the third FET is used as an oscillator.
But because the small PCB is pretty crowded (with a mix of SMD and through hole components) it feels like finding a needle in a haystack...

The main problem is that there is no oscillation, causing the microphone not to work.
Any suggestions where to find the (more recent?) version of a MKH40 schematic?

(In the attachment: the "old" version, anyway that is what I think.)

The schematic you've posted appears to be the one from the 2005 service manual -- and the pcbs listed with that schematic  look like this:
http://www.saturn-sound.com/images%20-%20microphones/sennheiser%20mkh40%20-%20inside%20views.jpg

I seem to remember some posts from John Willett on the Gearslutz forum that mention  'old and new' MKH40s, but I don't know  when the 'new'  model was introduced .. later than 2005 perhaps? (The original dates from 1985, IIRC)

I can't see why they'd fit FETs in this type of mic though....the whole concept of RF condenser mics is to be low impedance - so I can't see how FETs would offer any advantage over bipolars ...curious?....

Thank you for mentioning the name John Willett.
I contacted Mr. Willett and he gave me some hints where to get the schematic of the 'newer' MKH40.

Interesting --- that suggests there are at least 3 versions then!
The schematic you posted is the same as the one in the 2005 service manual, and the PCB associated  with that circuit is the one I  linked to  the photo from Saturn Sounds in my earlier post.
That PCB includes SMT components  - which were certainly not around when the MKH40 was introduced on the 1980s. ....So that suggests at least 2 versions up until 2005.
Your contact with John Willett suggests that the 'FET' version you have is even more recent.

I wonder how many versions there are in total?..