Sennheiser MD421-U still possible to repair ?

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panman

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The humbucking coil does not change the sound and the capsule of course has to be fully assembled to sound right, but even if not, the capsule should sound more or less "correct".
When I looked at the pics again, it seems what you have there is an attempted repair, that did not really succeed. Well, it usually does not, unless you really know what you doing, but a plenty of practise does it in the end. That residue should not be there. If it is sticky, you may be able to clean it off using vinegar or isopropyl depending on what glue was used. But that glue may also be in wrong places inside the diaphragm and then you have more to do. Better go step by step and see.
If the capsule has bass, but sounds "muddy", it is possible that the coil has gotten loose from the diaphragm. That normally can be seen when moving the diaphragm.
 

niva

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May 19, 2009
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Update!

I tried again 3 days later and... it works perfectly!

The diaphragm wasn't moving freely on all areas of the voice coil, that was probably due to the amount of isopropyl alcohol I had to use to get rid of the "gluey substance" on the diaphragm. I had low sound and it was muddy.

It was probably just "soaked" into isopropyl between the magnet and the voice coil, so it just dried up. Now it works like a new, well almost ;)

Thanks to all!
 

Whoops

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Nice that you were happy to fix it, congrats

Dou you have a known good 421 mic that you can compare the Frequency Response with that one?
 

niva

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May 19, 2009
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Yes, I'll do it later.

Now I am working on a MD409. You can see the discussion here:

 

wallyracer 449

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i have an md 421 u with no output i disconnected the bass roll off and still no output i took resistance and its 215 ohms what should i look for next thank you charlie
 

niva

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Connect the 2 wires (red, blue) and the ground directly to an XLR connector. If there is still no signal, there's probably something wrong with your diaphragm / voice coil...
 

wallyracer 449

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Connect the 2 wires (red, blue) and the ground directly to an XLR connector. If there is still no signal, there's probably something wrong with your diaphragm / voice coil...
I've done that and it has no signal , voice coil ohms out like it should what I can see of the diaphragm it looks good , can the coil/diaphragm be stuck it doesn't even do anything if I tap on it
 

Whoops

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i have an md 421 u with no output i disconnected the bass roll off and still no output i took resistance and its 215 ohms what should i look for next thank you charlie

You are measuring a dc resistance value in the correct range for these capsules which is somewhere between 200 and 230 ohms.
So the voice coils is good. it's strange that you don't have any output at all, maybe the voice coil is detached from the diaphragm. Or the diaphragm is loose on the sides or simply stuck
 

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