Sennheiser MD421-N Broken Roll Off Filter

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do0g

Member
Joined
Aug 31, 2008
Messages
15
Location
Manchester, UK
Hi all, I've posted this over at gearslutz but reckon I'd have a much better chance here.

Just wondering if anyone has had any experience with a broken roll off filter on a 421? Some peanut over-rotated the filter ring on one of mine and now it doesn't stop at either of the "S" or "M" positions.

Does anyone have any experience with repairing the filter? Is it impossible/easy/ludicrous to attempt? Any tips to share?

Thanks all,
Doug
 
Various ways that the thing can be broken but let's assume you only have the mechanical problem that the end-stops are gone, right ?


Exactly what mine had when I bought it. Only later I found out that it was 'locked' in the S-position, so lacking bass.

Most likely a small little part inside that fits into a little slot is broken.
Open the mic by removing the ring. Likely the broken pieces fall out. Put them together as an example
and try to clone it from a small piece of sturdy material. I initially used some PCB-fiber material but that didn't keep
doing the trick. Then someone broke another '421 beyond repair so I took the part from that mic.

IIRC the '441 uses an alike (probably identical) part.

Good luck !

  Peter 
 
buy the replacement part from Senn.  I replaced the entire case of one for about $50 total once. 
 
emrr said:
buy the replacement part from Senn.  I replaced the entire case of one for about $50 total once. 

Thanks for the info Doug, I'll keep that in mind if I don't have any success with the repair.

clintrubber said:
Open the mic by removing the ring.

I can see a circlip when looking directly at the pins of the tuchel connector, is this what you're referring to? Removing this and pulling the pin assembly out of the casing there looks to be a small screw underneath, will this release the roll-off assembly or am I barking up the wrong tree completely here?

Thanks!
 
do0g said:
clintrubber said:
Open the mic by removing the ring.

I can see a circlip when looking directly at the pins of the tuchel connector, is this what you're referring to? Removing this and pulling the pin assembly out of the casing there looks to be a small screw underneath, will this release the roll-off assembly or am I barking up the wrong tree completely here?

Thanks!

It's been a while, I know that there's also a screw underneath the serial-# label (in the mic-clip-slot), but you might not need to go there, that'll be for access to the 'real' inner stuff.

The M-S-ring slips on IIRC, and the click-click is by means of a small metal ball (don't lose that one, it'll jump out when removing the ring).

I'll have a closer look tonight, not near one now. And/or await info from someone for who it's been less long ago.

Bye,

  Peter
 
clintrubber said:
It's been a while, I know that there's also a screw underneath the serial-# label (in the mic-clip-slot), but you might not need to go there, that'll be for access to the 'real' inner stuff.

The M-S-ring slips on IIRC, and the click-click is by means of a small metal ball (don't lose that one, it'll jump out when removing the ring).

I'll have a closer look tonight, not near one now. And/or await info from someone for who it's been less long ago.

Bye,

Peter

Thanks for the info Peter. I just bypassed the roll off filter and think it may have suffered the same fate as yours - when bypassed the signal was noticably hotter (~4dB) than when running through the filter, and the filter settings aren't having any effect.

Did you manage to repair yours from this state, or should I be ordering a replacement? :)
 
do0g said:
Thanks for the info Peter. I just bypassed the roll off filter and think it may have suffered the same fate as yours - when bypassed the signal was noticably hotter (~4dB) than when running through the filter, and the filter settings aren't having any effect.

Did you manage to repair yours from this state, or should I be ordering a replacement? :)

My pleasure.

But please note that mine was electrically fully OK, it was just that due to the broken small thing the 5-pos
switch wasn't having any effect. And it was internally effectively at the 'S'-position, hence thinner sound.

Interting the 'replacement small thing' and aligning the switch made it fully OK again.

Bye
 
I've not yet managed to crack mine open to find the small piece that has broken - it seems to me that either the metal ring directly under the rotating roll off ring may unscrew, or the circuit board at the opposite end of the assembly to the pins may come out as well, but on my mic neither of these are happening!  ???
 
do0g said:
I've not yet managed to crack mine open to find the small piece that has broken - it seems to me that either the metal ring directly under the rotating roll off ring may unscrew, or the circuit board at the opposite end of the assembly to the pins may come out as well, but on my mic neither of these are happening!  ???

I had a look and that must be it, the metal ring 'between' the plastic switch control on one side & the actual connector on the other side.
Mine is a DIN-3, the ring has two small round holes, most likely for a special tool, but you might be in luck with a pair of pliers with sharp pins (that you don't mind to get bent).

Good luck
 

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