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Sennheiser Mkh40 popping
Old 14th May 2020
  #1
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Sennheiser Mkh40 popping

Hi, I was using my MKH40 yesterday and it seems to be suffering from random bouts of audio dropout and making a popping noise...it's like it looses phantom power for a split second. I have tried different cables/pres and it still does it.
Has anyone come across this before?
Thanks
Old 14th May 2020
  #2
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Not with my MKH40's but I have used Sennheiser service for other mics and they were quick and easy to deal with. Mics were perfect after they fixed them.

I do need to send in an MKH40 because something is rattling around inside, but it still works perfectly.
Old 15th May 2020
  #3
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Dry it in the sun.
Old 15th May 2020
  #4
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Quote:
Originally Posted by TSM View Post
Hi, I was using my MKH40 yesterday and it seems to be suffering from random bouts of audio dropout and making a popping noise...it's like it looses phantom power for a split second. I have tried different cables/pres and it still does it.
Has anyone come across this before?
Thanks
That happened to me with a pair of Gefell M200 omnis about 10 years ago. It was random, and was in one mic. Warm or cold, humid or dry (they were stored in an air-conditioned living space when not deployed)... it would work fine until it didn't. IIRC it took a trip to Gefell to cure.
Old 15th May 2020
  #5
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Other than the capsule, everything else on MKH40 can be fixed with off the shelf parts. Nothing unusual about it. If you have more than one of those microphone, you can swap the capsule to determine if the fault is within the capsule, or not. The replacement capsule is pretty expensive last time I checked with Sennheiser.


Good luck.


Da-Hong
Old 25th May 2020
  #6
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Mats H's Avatar
Quote:
Originally Posted by dseetoo View Post
Other than the capsule, everything else on MKH40 can be fixed with off the shelf parts. Nothing unusual about it. If you have more than one of those microphone, you can swap the capsule to determine if the fault is within the capsule, or not. The replacement capsule is pretty expensive last time I checked with Sennheiser.


Good luck.


Da-Hong
Hi, I have a faulty MKH40, which used to have some random pops, but now the capsule seems to have failed after a short fall from a chair. Could you disclose how much the capsule replacement was?
Old 25th May 2020
  #7
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Quote:
Originally Posted by Mats H View Post
Hi, I have a faulty MKH40, which used to have some random pops, but now the capsule seems to have failed after a short fall from a chair. Could you disclose how much the capsule replacement was?

Well, how do you know for sure the problem is in the capsule? Did you have someone look at it already? I ask this because from my experience the capsule rarely fails.


The last time I inquired about the replacement price, Sennheiser USA quoted me about $600 repair bill, all inclusive. I think the capsule is about $500 and labor $100. I don't know if they would charge you more for the repair if the service needed is beyond capsule replacement and calibration.
Old 25th May 2020
  #8
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Quote:
Originally Posted by dseetoo View Post
Well, how do you know for sure the problem is in the capsule? Did you have someone look at it already? I ask this because from my experience the capsule rarely fails.


The last time I inquired about the replacement price, Sennheiser USA quoted me about $600 repair bill, all inclusive. I think the capsule is about $500 and labor $100. I don't know if they would charge you more for the repair if the service needed is beyond capsule replacement and calibration.
Well I don't know, it could be some other component. It fell into a stone floor from about 45cm height. Haven't opened it up myself. It doesn't rattle when shaking it lightly at least. Thanks for that info, I've been a bit anxious about sending it in for repair.
Old 25th May 2020
  #9
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Unless it is verified by someone qualified, I wouldn't say the capsule needs replacement too quickly.

Take the capsule apart from the main body and you can measure the capacitance of both sides of the capsule. They are about 50pF each side. The absolute value is not as important as that they should measure the same. If they don't measure the same or they exhibit short circuit, it needs to be replaced.

The service manual is available on the net.
Old 25th May 2020
  #10
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The amount of shared knowledge in this forum is probably unmatched on the internet. I thank you so much for that valuable insight. I'll measure it soon and get a clearer picture of the damage before sending it to repair!
Old 25th May 2020
  #11
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I understand, with at least some older MKH models, the way the XLR is connected is prone to stress failure, and desoldering/tightening can be the fix.
Old 27th May 2020
  #12
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GIACOMO-_'s Avatar
 

Or buy my MKH40 with MZS40.
Old 29th May 2020
  #13
Gear Nut
I own 20 MKH series microphones. To get to the point, many years ago when the MKH 60 was introduced there were big problems with self noise. Design flaw so Sennheiser did free repair or outright replacement.
When the 8060 was released I bought a pair. Worked well until I was recording a documentary in Oxford, UK. Impromptu organ recording and I heard way more hiss is one of the 8060's than the other. Sent offending mic back to Sennheiser USA immediately when I got home. Was replaced without question. Now they have same beautifully low noise floor. So I would say send it to Sennheiser with a note and see what happens. BTW my other MKH mics have always performed perfectly over the years.
Old 29th May 2020
  #14
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MKH 8000 seem to have had more than fair share of issues.
Old 30th May 2020
  #15
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Update: Thanks for all the tips and advice I was going to get it back to Sennheiser. They offer a fixed fee repair for this mic. However before doing that, I thought I would open it up and just see if anything was amiss. Everything looked fine except the solder side of the pcb was very dirty with a chalk like substance over it. Maybe it got damp sometime before I bought it? Anyway, I gently cleaned it off with an old toothbrush. I left it on overnight recording nothing, and today I discovered no problem, working normally....maybe it was that?
Thanks
Old 30th May 2020
  #16
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John Willett's Avatar
 

Exclamation

Quote:
Originally Posted by dseetoo View Post
Other than the capsule, everything else on MKH40 can be fixed with off the shelf parts. Nothing unusual about it. If you have more than one of those microphone, you can swap the capsule to determine if the fault is within the capsule, or not. The replacement capsule is pretty expensive last time I checked with Sennheiser.
You CANNOT just swap capsules with the Sennheiser MKH microphone series.

They are RF condensers and the electronics HAVE to be adjusted and tuned to the capsule.

Swapping may highlight the fault but you must NEVER just swap the capsules over permanantly without them going back to Sennheiser for the electronics to be tuned and set-up for the particular capsule.
Old 30th May 2020
  #17
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Quote:
Originally Posted by Ontariosound View Post
I own 20 MKH series microphones. To get to the point, many years ago when the MKH 60 was introduced there were big problems with self noise. Design flaw so Sennheiser did free repair or outright replacement.
Correction - there was no problem with "self noise" on the early MKH 60.

When the MKH 60 was introduced it used the same chassis arrangement as the MKH 40 - but the 60 was mainly used outdoors.

The first time the BBC used it was to televise the Boat Race (Oxford vs Cambridge) on the Thames. They found that the MKH 60 picked up broadcast radio (which you may probably call "self noise" if it was picking up stray RF quietly - but it was not self noise at all).

Sennheiser re-designed the microphone chassis so that there was a Faraday cage around the electronics (if you open up a current MKH 60 you will see that the PCB is inside a metal box) - they recalled and replaced all the units that had already been sold.

No MKH 60 in use would have that problem at all as every one was replaced.

(For the record, I was working for the Sennheiser UK distributor at the time in Technical Support)
Old 30th May 2020
  #18
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Quote:
Originally Posted by John Willett View Post
You CANNOT just swap capsules with the Sennheiser MKH microphone series.

They are RF condensers and the electronics HAVE to be adjusted and tuned to the capsule.

Swapping may highlight the fault but you must NEVER just swap the capsules over permanantly without them going back to Sennheiser for the electronics to be tuned and set-up for the particular capsule.

Hi John,

First of all, my suggestion was only to identify the problem.

Secondly, you should give Sennheiser more credit on how closely they manufacture those capsules. I have more MKH microphones than I care to disclose. I have measured all the capsules my MKH microphones as I service all my own microphones. The capacitances variances are so small within each capsule, as well as between the different capsules of the same model they all work fine without any adjustment if you simply swap them. Yes, they might work slightly better if you tune the discriminator coil, but chances are they might not.

Thirdly, a slightly de-tuned MKH microphone is hardly acoustically measurable, certainly not sonically identifiable.



All the best,

Da-Hong
Old 30th May 2020
  #19
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Quote:
Originally Posted by dseetoo View Post
Hi John,

First of all, my suggestion was only to identify the problem.

Secondly, you should give Sennheiser more credit on how closely they manufacture those capsules. I have more MKH microphones than I care to disclose. I have measured all the capsules my MKH microphones as I service all my own microphones. The capacitances variances are so small within each capsule, as well as between the different capsules of the same model they all work fine without any adjustment if you simply swap them. Yes, they might work slightly better if you tune the discriminator coil, but chances are they might not.

Thirdly, a slightly de-tuned MKH microphone is hardly acoustically measurable, certainly not sonically identifiable.
Identifying the problem only - OK (as I said).

But definitely NOT a permanent swap without re-tuning.

Sennheiser were very firm on this - you must not swap capsules!

This is why the MKH 8000 series have all the electronics as part of the capsule.

People must NOT follow what you suggested and swap capsules.

I DO know these things - I was Technical Manager at Sennheiser UK when the MKH 8000 series was designed and I know the designers personally (I was with Sennheiser for about 25 years - from 1985 until 2010).

You must not swap capsules without retuning the electronics to match.

This is important.

If it was not important, Sennheiser would have made the MKH 8000 series with swappable heads - it's because they are not interchangeable that they included all the electronics in the head - the XLR is just a passive adaptor to XLR.

If you are happy to use de-tuned capsules, that's up to you - but I certainly would not and would insist my microphones were properly tuned and in full spec. I may not have as many MKH mics as you, but I still have about 14 in my kit.
Old 30th May 2020
  #20
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Quote:
Originally Posted by John Willett View Post
Identifying the problem only - OK (as I said).

But definitely NOT a permanent swap without re-tuning.

Sennheiser were very firm on this - you must not swap capsules!

This is why the MKH 8000 series have all the electronics as part of the capsule.

People must NOT follow what you suggested and swap capsules.

I DO know these things - I was Technical Manager at Sennheiser UK when the MKH 8000 series was designed and I know the designers personally (I was with Sennheiser for about 25 years - from 1985 until 2010).

You must not swap capsules without retuning the electronics to match.

This is important.

If it was not important, Sennheiser would have made the MKH 8000 series with swappable heads - it's because they are not interchangeable that they included all the electronics in the head - the XLR is just a passive adaptor to XLR.

If you are happy to use de-tuned capsules, that's up to you - but I certainly would not and would insist my microphones were properly tuned and in full spec. I may not have as many MKH mics as you, but I still have about 14 in my kit.


The slight amount of de-tuning happens when you swap a capsule often is much smaller than drifting naturally happens as the parts age. How often are you supposed to send your mics in for re-tuning?

If one could figure out how to take the capsule apart from the microphone, turning the circuit is a piece of cake. The procedure is documented in the service manual. All you need is a small plastic screw driver for tuning RF coils and a voltage meter. This is not rocket science.
Old 30th May 2020
  #21
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Quote:
Originally Posted by dseetoo View Post
If one could figure out how to take the capsule apart from the microphone, turning the circuit is a piece of cake. The procedure is documented in the service manual. All you need is a small plastic screw driver for tuning RF coils and a voltage meter. This is not rocket science.
But that's what you do - you don't just swap the capsule as you suggested.

The modern MKH are a lot more stable and tighter than the earlier (non symmetrical capsule) ones that used a crystal and had to be checked and re-tuned if they were dropped.
Old 3 weeks ago
  #22
Moisture or dust on the capsule. A capacitor on the circuit card going bad. Foreign substance on the solder side of the circuit card. Any of these could cause random noises. Best of luck in finding the problem. As others have said Sennheiser service is probably your best bet on getting it fixed. FWIW
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