u87 problems

I have an old 70's u87i that I just had re diaphragmmed. It sounded great for about 3 or 4 uses. It is now making a noise that sounds allot like wind blowing into the microphone. I tried it on several different pre's and it makes the same noise none the less. I have heard the noise before with old mic's being used without a pop screen.


Anyone have any input?

have you taken it apart? did you puncture a hole in the diaphram?

take a look around the edge of the diaphragm for dirt that may have gotten in there. If there is condensation or excessive moisture present on the capsule, that wooshing sound is the first sign on my mics, schoepps are really sensitive to that. Does the mic do it at idle or just after you speak into it?

dave

Like Dave posted it could be moisture and/or dirt at the edge draining the charge away and causing noise. Are you in a high moisture area are you using a pop filter?

Microphones can get a piece of dust at the edge and hold moisture Neumanns k87/67 capsules are sensitive to this.

Do you have a dry place you can place the microphone for a few hours and try it again?

I figured moisture or dirt myself. Two things that discount this. First it hasn't been used for vocals in a while and it has worked fine since then. When the probelm occured I was using it as a room mic in an air conditioned room. Also the capsule has been re-sputtered about 2 weeks ago. The capsule is clean as a whistle since all the gold is brand new.

re-sputtered ?????

sputtering is not the way to coat PET for a capsule.

The good rebuilders use e-beam or evap I believe

Who rebuilt it?

Did you send the whole microphone or the head or just the capsule?

never discount the stray bit of dust causing you a problem with the capsule.

[quote author="Gus"]re-sputtered ?????

sputtering is not the way to coat PET for a capsule.

The good rebuilders use e-beam or evap I believe

Who rebuilt it?

Did you send the whole microphone or the head or just the capsule?

never discount the stray bit of dust causing you a problem with the capsule.[/quote]


My apology, my terminology not theirs. Korby Mics did it. They have always a great job. I don't now what they call it but it looks brand new.

..the u87 (and the u67/m269 as well) capsule is known to be very sensitive to humidity, meaning that using it for vocal without sufficient pop-filter will result in an error exactly like the one you describe..

If it isn't noisy when allowed to dry - i.e. not being used for vocals - then it's probably completely alright.

Jakob E.

It could be the electrolytic/tantalum caps, bad solder joints, or dirty switches or connections between the main electronics and the head assy(upper part with capsule, caps, and switches).

..the u87 (and the u67/m269 as well) capsule is known to be very sensitive to humidity, meaning that using it for vocal without sufficient pop-filter will result in an error exactly like the one you describe..

Click to expand...

Jakob, it is really interesting you mention that. I have a 70ies U87 as well and it can only be used with a pop stop for vocals, one breath and it breaks down. I wanted to switch the capsules around as it is used 90% in cardioid mode.

I have worked on a number of early 70's 87s.

Never had any problems with the circuit or parts like the caps.

All the problems I worked on were just dirty capsules or bent up metal parts like the grill or body from being dropped.

Now if you have not cleaned a capsule or tried and destroyed one or more, do not learn/work on an old capsule that has any value.

Well, I've worked on a number of 70's U87's and have run into bad tantalum caps, broken solder joints, dirty contacts on the slide switches in the head and in the XLR connector, spread sockets where the head pins insert,...