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[klaus]

Originally Posted By: pruner1 on Wed, 09 March 2011

Hi All. New to the forum. Found it while investigating my U47 problem.
 
I have wind, rumble, and pops randomly. Sometimes it's not there at all and the mic is very quiet. It comes and goes without warning.
 
U47 has the rca nuvistor. Capsule was replaced 15 years ago. Custom power supply was built when the mic was rebuilt.
 
If this were the capsule, wouldn't it make the sound constantly?
 When it's not there, the mic is fine and sounds great.
 
Here is a link to the noise.
 http://www.cattraxrecording.com/U47_noise.mp3
 
Any opinions would be appreciated. Just trying to diagnose it so I can figure out how much the repair will be. Also who should I send it to to be fixed? I live in upstate New York.
 
Thanks,
 Josh

[ttown]

Hi Josh, I had a very similar issue with my Gefell 582 with M70 capsule. 
It turned out to be dirty contacts on the mic.  I used some Q-tips with Deoxit cleaner and it sorted the problem out completely.
I pulled off quite a bit of oxidation in the process!
Good luck
-Terrence Town

[soapfoot]

Since the mic needs work anyway, would you ever consider a complete restoration with a proper tube and capsule?  That would probably help you get the most out of your mic.  Most share the consensus that with a nuvistor tube (rather poor match for the BV8 transformer), and without either a proper M7 or K47 capsule, you're not getting the most out of what should be a very fine microphone.  If you enjoy its performance as-is, or are on a severely limited budget, that's one thing. The mic could always be restored in the future.

You've come to a good place. The people on this forum are very knowledgeable and can tell you anything you'd ever want to know about your U47.

[klaus]

As mentioned here often before: remote trouble shooting of a mic's problem is hairy, so I often advise: separate capsule issues from amp issues whenever you can.

In this case, if you have another U47 head available, even if it's just for a few minutes, you can quickly verify where the problem lies: the noise will either say with your capsule or mic amp.

Regarding the idea of "upgrading" your mic back to stock: it seemed from your description that you have a K47 Neumann already in there? If that is so, it's one of the finest capsules Neumann has ever made, (and still makes!) and came stock in all U47/49 around 1959/1960. So if it was replaced 15 years ago with a Neumann capsule, that would have been the one.

I agree with trying to find a VF14. The expenditure will be recouped, dollar for dollar, to the mic's current collectible value.