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Sennheiser mkh405 problem



 
 
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  #1  
Old October 8th 20, 11:27 PM posted to rec.audio.pro
Rick Ruskin
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Posts: 358
Default Sennheiser mkh405 problem

I fired up my pair today and found 1 is working while the other is has
a very distorted output. I know these mics tend to drift out of spec
but might it be something else and is there a way for a non-tech to
troubleshoot it? Right now I'm leaving it powered up to see if it
might correct itself but I'm not holding my breath.



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  #2  
Old October 9th 20, 03:18 AM posted to rec.audio.pro
Scott Dorsey
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Default Sennheiser mkh405 problem

Rick Ruskin > wrote:
>I fired up my pair today and found 1 is working while the other is has
>a very distorted output. I know these mics tend to drift out of spec
>but might it be something else and is there a way for a non-tech to
>troubleshoot it? Right now I'm leaving it powered up to see if it
>might correct itself but I'm not holding my breath.


1. Check the diaphragm. Is it damaged? Shine a flashlight and make sure the
surface is flat. The capsules on these don't go bad easily but if they do
I don't think anyone can reskin them.

2. There are three or four small electrolytics in there. Do they test good or
are they leaky? Use an ESR tester on them. My personal inclination about
electrolytics of that age is to replace them rather than testing them, but
it's very tight in there and you will need a precision solder removal tool.
Changing them is not for the faint of heart.

Beyond that point you're going to be checking the RF stuff. I have seen the
silver mica caps go bad and the oscillator frequency drift way off once, but
I can't imagine it's that common a failure. There really isn't that much
to go wrong in these; they are not that complicated, but they are RF systems
so they require having your head in a different place than conventional
audio gear.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #3  
Old October 9th 20, 03:48 AM posted to rec.audio.pro
Rick Ruskin
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Posts: 358
Default Sennheiser mkh405 problem

On 9 Oct 2020 02:18:39 -0000, (Scott Dorsey) wrote:

>Rick Ruskin > wrote:
>>I fired up my pair today and found 1 is working while the other is has
>>a very distorted output. I know these mics tend to drift out of spec
>>but might it be something else and is there a way for a non-tech to
>>troubleshoot it? Right now I'm leaving it powered up to see if it
>>might correct itself but I'm not holding my breath.

>
>1. Check the diaphragm. Is it damaged? Shine a flashlight and make sure the
>surface is flat. The capsules on these don't go bad easily but if they do
>I don't think anyone can reskin them.
>
>2. There are three or four small electrolytics in there. Do they test good or
>are they leaky? Use an ESR tester on them. My personal inclination about
>electrolytics of that age is to replace them rather than testing them, but
>it's very tight in there and you will need a precision solder removal tool.
>Changing them is not for the faint of heart.
>
>Beyond that point you're going to be checking the RF stuff. I have seen the
>silver mica caps go bad and the oscillator frequency drift way off once, but
>I can't imagine it's that common a failure. There really isn't that much
>to go wrong in these; they are not that complicated, but they are RF systems
>so they require having your head in a different place than conventional
>audio gear.
>--scott



Thanks. I'll contact Sennhieser tomorrow to see if they still service
this unit. The caps have been obsolete for decades now but I suspect
something else has bit the dust.




Rick Ruskin
Lion Dog Music - Seattle, WA
http://liondogmusic.com

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  #4  
Old October 9th 20, 03:51 AM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 498
Default Sennheiser mkh405 problem

Scott Dorsey wrote:

===================
>
>
> Beyond that point you're going to be checking the RF stuff.
> I have seen the silver mica caps go bad and the oscillator
> frequency drift way off once,
>

** While silver mica caps certainly can go short, the MKH405 uses an 8MHz crystal.

http://www225.pair.com/audio/waltzin...er/MKH-405.htm


Anything might go wrong with a 50 year old RF mic.


...... Phil


  #5  
Old October 9th 20, 05:29 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,759
Default Sennheiser mkh405 problem

Rick Ruskin > wrote:
>
>Thanks. I'll contact Sennhieser tomorrow to see if they still service
>this unit. The caps have been obsolete for decades now but I suspect
>something else has bit the dust.


I'd ask them to recap both of them when they fix one, so that you'll have
a pair that are reasonably matched. They are both overdue for that sort
of maintenance.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #8  
Old October 16th 20, 01:39 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,759
Default Sennheiser mkh405 problem


Try Location Sound Corp. They do 805s all day long, they should have no
problem with a 405. If they don't want to touch it, I'll look at it, but
they are good people.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
 




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