Sennheiser MD409-U3 still possible to repair?

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niva

Member
Joined
May 19, 2009
Messages
16
Hello!

Attempted to clean the diaphragm of this "nice looking" Sennheiser MD409. There was unknown debris and some gluey substance on the diaphragm.

At first, the mike was still working but was sounding very dull.

After carefully and successfully cleaning the membrane, the capsule just died: the voice coil mesures infinity.

You can see on the picture that there is a small piece of red enamel wire in the center of the diaphragm (inside).

So... is there something I can do myself? Or anybody out there that could repair it?

I could ship the capsule anywhere.

Thanks!

Guillaume, Québec, Canada
 

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panman

Well-known member
Joined
Feb 8, 2014
Messages
110
Location
Switzerland
That peace of coil in the middle and the looks strongly indicate, that it was "repaired" before. By cleaning the gluey substance from the diaphragm you unfortunately managed to cut at least one of the coil ends and so the mic is dead now. From now on it really is not DIY-job anymore. Nevertheless, it is not forbidden to try. The diaphragm needs to be removed(without destroying it!). The broken coil-end is now too short and the other one may also be broken or will likely be broken when you have managed to remove the diaphragm. Then the coil end(s) need to be pulled out to be long enough, but only one end is possible to be pulled out by you, if you are lucky. The other one? Well, that requires professional skils and experience. If it is long enough to be soldered back, fine. Then you need to clean off all the glue from the capsule and the diaphragm and also the magnet gap has to be cleaned from iron particles. Now let`s hope one of the coil-ends came out enough and also the other was not cut(you managed to solder it out and it did not brake). Now the coil-ends will be soldered to the lugs. Then the diaphragm can be glued back with slow drying glue, that you can center and tune it to sound right. Carefull, that the glue is not going to wrong places! It is important to check, that the diaphragm is perfect and without dents. The dents usually can be pushed out from underside, but if any tiny defect remain, it will not sound with full bass. You also need a known to be fully to specs MD409(they rarely are) to know if your repair sounds right. Good luck! And even if your trial goes ashtray, you can always send it to me for repair.
 

panman

Well-known member
Joined
Feb 8, 2014
Messages
110
Location
Switzerland
Especially the MD409-U3 and BF509 models seldom sound right, because the black plastic-foam used as a shock-mount/windscreen has deteriorated into sticky goo and penetrades under the reflector sticking on the diaphragm. Many times it is too late to save the diaphragm. Those foam kits are still available or they can be replaced with foam, that has the same properties.

DSC01357.JPG
 
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