U87 capsule problems

Hi all, I have that U87 mic for repair. The customer told me that it stops sounding when record voices but not with instruments. It sounds to me the "typical" problem with moisture that makes dust conductive with humidity... I think that, normally, it can be solved cleaning the gold free pvc/mylar area. The problem came when I opened the mic. There are dust, yes, but I see also that dark area arround central terminals, front and back. I don't know what exactly is that dark coloration, seems like oxidation? it needs to be reskined or it can still be ok only cleaning the pvc gold free area? I'm not sure what to do with that.
If someone knows what's it or how to proceed  I woluld be bery grateful.






Thanks!

Arnau

Jepp - this is the moisture issue...
The residue on the plastic rings look like nicotine to me.
On one side the gold is already coming off...
Not sure what the blueish circle in the middle of the diaphragm is. It could indeed be some oxidisation.

Send this capsule to Thiersch for reskinning. Cost was approx. 100 EUR plus shipping the last time I sent one of my capsules to him.

This capsule has been probably reskinned !
look at the bad centering of the sputtered area
i add that there's probably a hole in the rear membrane
the oxydation is the cherry on the cake for a supposed gold sputterization

amateurish job

look at Peter Drefahl for reskinning

Unfortunately Neumann was famous in the past for bad centering.
I have two K87 here that are also loosing their gold sputtering and this looks similar to the one on the picture.

chefducuisine said:

Unfortunately Neumann was famous in the past for bad centering.
I have two K87 here that are also loosing their gold sputtering and this looks similar to the one on the picture.

Click to expand...

true , neumann tolerates a little uncentering but not at this point

be careful if you clean the mylar zone, there's a hole in this area, some liquid could flow under the diaphragm  ...

Thanks for your tips  . Yes there is not very good centered. I saw the gold loosing. I'm not sure about the hole...on pic it seems a hole but I remember that is like a peace of gold, I will see when I open it again. I'm asking prices for reskinning it. I was thinking for its age it would be a pvc capsule but I'm not sure about it.
Thanks again 

mylar for k870
pvc for M7

the hole in the mylar area is made by Neumann, it's normal , for air pressure balance

the probable hole on the gold area is another story...

If the capsule is genuine, the oxydation comes from the center screw and connector, it has contaminated the mylar because  the sputterization is probably too old...

did they use and store the mic in a moistened place ?

this should have an  effect on the capacitance...
can you measure both sides capacitance...?

It may be best to reskin it..  I would do it for a good price.  It would look much better as well.

Eric

Hello, the capsule should be re-skinned. 

Plus someone has poked a small hole in one of the diaphragms which usually happens when a slot screwdriver slips. 
The hole looks like a gash from a small flathead screwdriver in my experience.

The Chinese actually use Philips screws in a lot of their capsule and the gold sputtering binds much better to the mylar than the Neumann builds but that microphone has worked for at least 30 years.

It looks like a U87i which was first introduce in 1968 and in 1986 Neumann introduced the U87Ai.

So, that microphones is anywhere from 30 to 47 years old.

That is typical of Neumann U87 microphones.  The gold sputtering wears off from the damp breath of close vocals. 

The damp breath also picks up dust particles in the air and deposits them on the diaphragm.

I have turned the capsule around in several U87's which will extend its life in Cardiod but that capsule has been badly compromised on both sides.

Cheers, Dave

Thanks all for your advices We finally sended it to tiersch for reskinning it. We are now waiting for its return, and test it 

Well, few weeks ago capsule reskinned arrived. I looks very nice  . They replaced aluminium thin spacers that are too deteriorated. I just mount it and mic works fine.  Sadly I couldn't did properly tests or comparisions with it, the owner neded it for some recordings inmediatly...
These pics are how it looks when it returned from tiersch.




Thanks All again !! 

No conservation gloves?