Sennheiser MKH 416 P48 sputtering noise / dead --- schematics?

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s113

New member
Joined
Sep 10, 2018
Messages
2
Hi,
I have an ancient brownish-grey MKH 416 P48 with DIN
connector, unfortunately I need to fix it now.

Could anyone help me with schematics / service manual?


The mic was fine, though sometimes produced a sputtering noise,
the effect did not react to movements. Probably caused by a
defective component (semiconductor, tantalum). Annoying but
harmless, I was about to "blindly" change caps etc..

But... meanwhile the mic deceased at -15 deg C outdoors.
(Aren't these mics frost-safe?)

The DC-on and off plop signals still look normal (as before)
but there is no audio anymore. Possibly oscillator dead.
Any ideas, what could have happened?

It would be much easier for me to find the culprit(s) if I
could exactly know the thing. I have obviously different
older and newer MKH schematics. but not the one I need.

Thanks a lot
David

 
You should check the capsule and quartz crystal  (8MHz) in the oscillator. I have  the schematic somewhere but can't find it now. I will check it in next few days and get back.
 
There's a pdf out there somewhere labeled mkh415 which has schematic and full service procedure.  Probably close enough. 

I've also been told the following:

on the MKH 416, 816, 415, 815, 405, 435, and 406 mics, (pre SMT) its the same routine- sub a 27pf capacitor in place of the capsule and adjust the transformer closest to the capsule for 0mv,  +/- 50mv, at points A and B, which are easily located by the protruding test pins soldered on the foil side.   Sennheiser interchanged the designators L1 and L2 at some point in the development of the MKH series.  I leave the center coil alone. If there is a 3rd coil, it is the 8mHz frequency adjustment, and I set it for 8mHz using a receiver. The early models use a crystal; the most recent MKH versions use an 8mHz ceramic resonator. Then a drop of candle wax over each slug. 
I believe all the adjustments are pretty broad. Its tough to make these mics fail. Typical repairs include open RF blocking inductors at pins 2 and 3, failed crystals or cracked/loose ferrite transformer enclosures, failed chassis-to -circuit board solder points from a previous repair, and failed tantalums.  Even a capsule that presents shorting can be resurrected with a couple of good raps on a table. Also the XLR pin assembly on all models is held only by a compression ring, and is somewhat wobbly. Enough years go by and one of the internal leads will break free.
 
Thank you so much. Printed schematics make things much easier than re-engineering.
Some component values differ between versions pre/post 1978 etc. but the circuitry
seems to be the same. MKH415 and MKH60 are very different from 416 though.

In my case the first PNP transistor in the output stage was dead.
Obviously a broken bond (that may have caused the occasional sputter sound before, too).

There is still one problem: A loose part of damping material moving in the plastic "flute" tube
that alternately sits on the capsule housing or remains in the metal cover. I'm not quite sure
were this damping wadding belongs best...

Does anyone have an exploded view or other type of picture?

 
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