U87 capsule pictures & problems

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zebra50

Well-known member
Joined
Jun 4, 2004
Messages
2,943
Location
York, UK
KidSquid was kind enough to mail me these pictures of U87 capsules. I think the capsules have seen some use and abuse...

"The pics of the mics are of a U-87, a U -87ai - these two have been
given to me for repair, when you see the pics, the U-87's top connector plug, has previously been through various states of repair. both the 87's , it seems, have got really dirty capsules, and the u87ai has got a scratch in the capsule ???, both mics make a cyclic wooshing sound. the 87ai is also getting high frequency distortion on peaks. i'm thinking maybe dirty capsules ?"

u87capsule2.jpg


u87capsule10.jpg


u87capsule5.jpg


u87capsule8.jpg
 
I would try using an air bulb with light bursts of air to knock some of the junk off. I would then try distilled water and a cotton ball. If thats does not clean a try an alcohol water mix. With the neumann style capsule You need a good optic brush to get the junk that causes a High Z connection from the gold to the edges. That is the stuff that gets conductive and leaks the charge from the gold all kind of problems and noise.

The Josephson writeup is very good.
 
Cheers for hosting the pics Stu, :thumb:

Going to have a go of cleaning the capsules over the weekend, most probably sunday nightshift !, so I'll let you know how it goes !

Gus, where can i get my hands on the josephson article ?

Cheers Lads :guinness: :guinness:

Steve
 
I can't help you with cleaning it, but I can tell you how I destroyed a perfectly good Rode capsule. I used alcohol on it, not knowing a thing about capsules. Stupid, yes, but I never thought in a million years that I would rub the sputtered gold right off. Well, that's what happened. I then had a nice mic that produced very little sound, and a LOT of hum.

Moral of the story, be REALLY careful. Depending on the capsule, you can very easily make the gold flake right off.

On the other hand, Stephen Paul said that you could probably put rubbing alcohol on one of his capsules because they were so well built. He said you shouldn't do that, but that he believed his capsules would stand up to the abuse. I'm guessing the Neumann is probably a lot better capsule than the Rode, but you still never know...

Good luck!! You should post after pics and let us know what you did...
 
Tubejay,

For a long time I have been wondering if diaphragm made conductive by rubbing graphite into it would work in a mic. Your capsule would be perfect to experiment with. If you don't need it could you send it to me?

[email protected]
 
[quote author="Marik"]Tubejay,

For a long time I have been wondering if diaphragm made conductive by rubbing graphite into it would work in a mic. Your capsule would be perfect to experiment with. If you don't need it could you send it to me?

[email protected][/quote]

Does someone else have a fried capsule they could send Marik? I sent the Rode back to Rode (out of warrantee) and they replaced the capsule for free. They kept or threw away the fried capsule when they fixed it.

If someone else had a capsule, it might be a good experiment... :thumb:
 
I recall a discussion on RO about using graphite or that sort of thing for the diaphragm. I think there's a problem in getting reliable connections, and also at high frequencies, even the resistivity of a thin film of graphite will become an issue. The capsule would act as a distributed pile of capacitors, resistively coupled. Especially at high frequencies. It might work, though.

I think a group from RO were looking at ordering some precoated material (gold), but you would need to use an edge terminated capsule - the standard Neumann-style with centre termination will not work with that material. I'm trying to put together a vacuum deposition system and if things go well I might try doing a diaphragm next weekend.
 
Hello Chaps,

Just Writing to say THANKS :grin: :grin: ,
I cleaned the two U87 capsules on sunday nightshift, fired them up on monday, and ive been using them untill i give em back tomorrow !!

The both mics are like new. :thumb:

anyway, off to finish some tracks - see you laterz
:guinness: :guinness:
Steve
 
Sorry Tubejay,

after listening to stewart ( zebra50), and the josphson article, i bumped into Otto - the Rockfield tech.
after a cuppa, he told me how he cleans their neumann's

using distilled water, cottonbuds wrapped in cotton wool, and blotting paper.

first, apply distilled water to some cotton wool, then soak up some water, and then cover the front diaghpram with the water. wash the dust particlesoff the capsule (very gently !)

cut the blotting paper into strips - then round off the corners with a scisors.

now use the blotting paper to soak up the excess water. repeat for other side. then put in a dust free zone to finish drying off.

works a treat :grin: :thumb:


Also Otto told me that a quick way to check neumann mics.

take the capsule / grille assembly off the mic, plug the mic in, and if the mic circuitry is o.k., the headless mic, will hum like crazy - proving that the diagphram is at fault - no hum - mic circuitry is at fault .


Anyway hope this little piece of info can help someone !
:guinness:

Steve
 
Blotting paper is a kind of paper made to soak up liquid. Blot means to gently touch something without rubbing it.
 
[quote author="tubejay"][quote author="Marik"]Tubejay,

For a long time I have been wondering if diaphragm made conductive by rubbing graphite into it would work in a mic. Your capsule would be perfect to experiment with. If you don't need it could you send it to me?

[email protected][/quote]

Does someone else have a fried capsule they could send Marik? I sent the Rode back to Rode (out of warrantee) and they replaced the capsule for free. They kept or threw away the fried capsule when they fixed it.

If someone else had a capsule, it might be a good experiment... :thumb:[/quote]

Marik,

I've an old CK12 capsule I could off to ya. I did a capsule replacement on the 414 it was in( the mic frick'n sings now), but kept the old one hangin around.

Oops, your email is right there, now isn't it :oops:

regards

ju
 

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