Russian mic advice

[hodad]

http://www.steambadger.com/thom_stuff/mk14m%20ext.jpg
http://www.steambadger.com/thom_stuff/mk14m%20int-1.jpg

So I stumbled upon this mic--an Oktava MK14M, an SM69-ish stereo mic. Unfortunately it had no power supply or cable.  After a good bit of digging I found out it was modded with tube electronics by AEG.  I contacted AEG.  After a while I managed to get a power supply from them (a Neumann NSMa, which is what they originally supplied with these mics), and the appropriate connectors and some cable.  Unfortunately, AEG can't seem to dig up info on how to connect the 10-pin mic to the 12-pin power supply, or an accurate schematic--I'm sure it's been a decade or two since they did the work, so I can't say I'm too surprised. 
I've tried almost everything I can think of to get it sussed out, but I'm coming up short.  I think I know the audio outputs, the plate, & chassis ground.  But I can't figure out filament, polarity pins, & 0V (at least that's what I'm assuming the rest of the pins are.)  The thing I have not done is pop one of the boards out to trace the circuit.  I've put a lot of effort into getting this far with this mic, & I'm not confident I won't screw something up if I take it apart.  I know there are quite a few folks here with far more experience inside Russian mics than I have, & I was hoping for some advice either on how to proceed myself, or suggestions about having someone else deal with it.  I'm a bit frustrated, uncertain, & hesitant.  But I really want to get this thing working.

 

[pucho812]

well figure it's like having 2 mics in one so each mic having a balanced out will take up a total of 6 pins hot cold and ground unless of course the tie the grounds together then it will be 5 pins., that only leaves you with 4  or 5 to really worry about...

 

[rodabod]

That is one seriously cool mic.

Valve looks to be a 6S31BR.

I'd recommend tracing the circuit. It shouldn't be too tricky. Also, can you take a photo of one of the capsules? It'd be interesting to see if it might be one of the M7-style caps or the CK12-style unit from the 19A19.

 

[Marik]

I had this mic awhile ago--it was unaltered SS version and I played with it quite a bit. The capsules are M7 style, however, the way they are mounted screws things up, so the resonator jobbies (for some reason Russians loved that one) are serving to make up for top response loss. I'd re-machine those and take off the resonatorts.

As Roddy has said, it is not a big deal to trace it and there is no reason for frustration. If you feel uncomfortable to deal with this mic yourself I'd highly suggest to ask somebody who has an experience with those things. I actually, would be interested to look at it myself (even just to remember this mic and see how it sounds tubed), but I am booked for awhile, so if you are in rush maybe try to contact Gus.

Best, Mark  

 

[hodad]

For rodabob:
http://www.steambadger.com/thom_stuff/mk14%20caps.jpg

I think I'm going to give a shot to tracing the schematic using a flashlight to give me a better look at the traces.  The thing about pulling a board out that makes me uncomfortable is desoldering the capsule leads--that, and figuring out how to get everything together again once I'm done.  If I make any headway on a schematic, I'll post here.  Otherwise, I'll probably send to Mark or Gus.

Thanks
Tom

 

[zebra50]

That is awesome, and looks in great shape! Good luck and do post back with your findings.

 

[Sonic]

Judging by last photo, a cap of type M7, but not CK-12 or LOMO 19a-19. Similar a cap stood in LOMO19a-1.

 

[Marik]

Judging by last photo, a cap of type M7, but not CK-12 or LOMO 19a-19.

Wasn't that what I just said a couple messages above?

 

[rodabod]

Judging by last photo, a cap of type M7, but not CK-12 or LOMO 19a-19.

Wasn't that what I just said a couple messages above?

Yes. I think Sonic maybe uses a translator to help read/write posts though which can be slightly confusing.

Tom - looking forward to seeing any sketches of schematics if you get a chance.