Sennheiser MKH416T repair

[The Documentary Sound Guy]

If it were me, I'd use the Sennheiser BP-2 that wyseacre recommends for power conversion, and do the Teuchel conversion separately in a cable.

Who is doing +48V conversions in Canada? Would love a domestic option...

 

[Icantthinkofaname]

If it were me, I'd use the Sennheiser BP-2 that wyseacre recommends for power conversion, and do the Teuchel conversion separately in a cable.

Who is doing +48V conversions in Canada? Would love a domestic option...

Nobody in Canada, I'd have to send the mic to Europe, but I have the Tuchel version so it's not an option anyway. If I can find the Sennheiser BP2 I'll get one, but I'm not seeing any for sale.

 

[Voyager10]

Ok, I've had a chance to re-test the DC voltages on the PCB with a 27pF capacitor instead of the capsule.

The new voltages that I measured are:

• +8.94V @ C15 (nominal +9.8V)
• +6.61V near solder point 8 (nominal +7V)

These aren't correct, but perhaps they are correct enough compared to the previous test?

In the name of science I measured a couple of my own mics at these points.

A 416T (with a working capsule) measured 9.78V @ C15 (pretty close) but 7.38V at C5 +ve.

My 406T (the capsule repair one) measures 9.93V @ C15 and 7.13V @ C5, with a 27pF capacitor in place of the capsule (and L1 trimmed accordingly). Removing the 27pF gives 10.23V @ C15 and 7.44V @ C5.

So there's quite a bit of variance from the nominal values, between mics. I'd say your measurements are within the same bounds and there's no reason to suspect the electronics are misbehaving.

For the avoidance of doubt - the voltages are measured with respect to "T-power negative", i.e. XLR or Tuchel pin 3. With a typical T-power adapter (180R in series with each of + and -), pin 3 is roughly 1.1V above ground / screen / XLR pin 1.

 

[The Documentary Sound Guy]

Thanks for the data. I'd judge the variances I measured to be significantly larger than yours (on the order of 10%), but for now, I agree that it seems close enough. I think the reference measurement may be part of the reason as well. I measured with my negative probe at the point marked 0V on the schematic (ground rail?), not at pin 3. So, that's a possible reason my results don't match. In any case, I appreciate the confirmation that my electronics are *probably* working.
Still working on getting into the capsule.

 

[mrclunk]

I've a bunch of these and have repaired a few.

Probs not your issue but worth adding to this thread...
A very common fault is a dry/cracked 0V joints between the shell and the PCB. There's a few different places where these occur. Re-solder all of these. Symptoms are increased noise, cracks and pops.

I've also made a little smt pcb for P48 > T12 conversion that fits inside the mic barrel next to the xlr.
Pm me if you want me to chuck one in the post?

 

[Jonnie m]

Since you're on the topic of mkh mics, do you mind me asking if any of you have a service manual for the mkh 406 P48? I've one with a broken 2.2nF capacitor that I'd like to mend. Also on a similar vein, do any of you know whether all of the mkh405s require 10V supply, as per the original catalogues? cheers

 

[Tubetec]

Theres a few of the service docs on the MKH mics posted in the documents section ,
and a few other threads on the subject that crop up from time to time ,
a search should find them .

 

[Jonnie m]

Theres a few of the service docs on the MKH mics posted in the documents section ,
and a few other threads on the subject that crop up from time to time ,
a search should find them .

Thanks for that - i have checked and there’s nothing, yet, for the 406. I’ll be sure to upload one should i find one. The stuff that’s there is handy for some of my others. Cheers

 

[Tubetec]

I have pair of 416's I picked up , outer case missing , parts from the internal windsheild gone , one is the p48 modern SMT version , the other is the XLR T powered version . With an external box there always remains a chance it gets directly connected to phantom power accidently , the mini pcb that fits inside the mic is a much safer bet in the music studio environment.


https://groupdiy.com/search/220855/?q=sennheiser+mkh&o=relevance
The 416 service docs cover a range different eras of the RF microphone , even if you dont find the service doc for what you want , all the procedures , tests and checks are the same , so all you need is the schematic for the mic you have and the service documents for the 416 explain the theory of opperation of the circuit .

 

[mrclunk]

Thanks for that - i have checked and there’s nothing, yet, for the 406. I’ll be sure to upload one should i find one. The stuff that’s there is handy for some of my others. Cheers

I have a couple of 406T, converted to P48, if you'd like me to measure anything.
Pretty sure the internals are the same as 416, apart from capsule.

 

[Voyager10]

There's a 416T service manual which includes the 406T.

In the Sennheiser tech docs thread Sennheiser

Direct link: https://cdn.imagearchive.com/groupd...55e6289e8a3c5d085a815e5c9a4e1bc2da5f2d206f2f0

 

[The Documentary Sound Guy]

Voyager10 beat me to it. But yes, the 416T service manual also includes a schematic and repair docs for the 406T.

 

[Jonnie m]

Thank you, I’ll check them out. Does anyone know whether these 2.2nf capacitors are tantalums? And what voltage I should use? I’ve got some 50v but I’d assume I ought to use about twice that? Cheers

 

[The Documentary Sound Guy]

The repair manual lists 2.2nF, 50V, 10%, X7R, which I believe makes them ceramic.

 

[The Documentary Sound Guy]

Also, KERKO as the brand.

 

[Jonnie m]

Brilliant, thankyou

 

[Tubetec]

The smaller blue pillow shaped caps will be ceramic ,
The larger blue and green epoxy dipped rounds ones are most likely Tants .

 

[Jonnie m]

The repair manual lists 2.2nF, 50V, 10%, X7R, which I believe makes them ceramic.

Excellent - I do like it when I find that the ones I happen to have are bang on spec. Cheers

 

[Jonnie m]

I've a bunch of these and have repaired a few.

Probs not your issue but worth adding to this thread...
A very common fault is a dry/cracked 0V joints between the shell and the PCB. There's a few different places where these occur. Re-solder all of these. Symptoms are increased noise, cracks and pops.

I've also made a little smt pcb for P48 > T12 conversion that fits inside the mic barrel next to the xlr.
Pm me if you want me to chuck one in the post?

Are the pcbs something that you sell?

 

[mrclunk]

Are the pcbs something that you sell?

PM me your address, i'll send you one.
I'm planning on selling them, populated, in the future. These are protos.
I've used them in a few of my mics.
Don't have much spare time at the mo...