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Author Topic: Broken 1959 Neumann U47  (Read 2927 times)

studiofocusrec

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Broken 1959 Neumann U47
« on: November 11, 2014, 01:55:19 pm »

Hi there. I run a studio just outside of Oxford in the UK. I have come across a 1959 Neumann U47 which is not working.

The mic has a newly built PSU+cable. I have the original VF14m tube and a brand new Telefunken VF14K (which should apparently work in an original 47 too). The rest of the mic appears to all be original.

I'm not experienced with vintage mics at all which is why I've come here to gather help (thank goodness for the internet!).

The problem with the mic is that it only outputs noise, no useful audio. The noise is very active, it sounds almost like a sandstorm. It is a beautiful sound, but I would prefer the sound of a working mic of course!

Is anyone here able to identify which component might cause this kind of noise?

Also, is anyone here aware of anyone within the UK who is able to service these kinds of mics?

Thanks for reading, and if anyone can help at all - that would be really fantastic!

Cheers!

Mike.

www.studiofocusrecording.com
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Uwe

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Re: Broken 1959 Neumann U47
« Reply #1 on: November 11, 2014, 03:41:21 pm »

From your description I would first suspect the VF14, then the capsule. In the UK your best bet for service will be:

Sennheiser UK Ltd
Pacific House, Third Avenue, Globe Park, Marlow
Buckinghamshire SL7 1EY
Great Britain
Tel.: +44 (0) 1628 402200
Fax.: +44 (0) 1628 402201
E-mail: info@sennheiser.co.uk

Good luck!
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klaus

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Re: Broken 1959 Neumann U47
« Reply #2 on: November 11, 2014, 05:55:16 pm »

From your description I would actually NOT suspect the tube (though it my be a secondary cause of additional noise, down the road).
Usually when there is a hefty amount of noise output, the high impedance section is not functioning properly: either the capsule is defective or a connection or component between capsule and grid of the tube is suspect.

P.S.: I hope there is enough institutional memory and work experience about U47s left at Sennheiser Great Britain to serve you well!
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

studiofocusrec

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Re: Broken 1959 Neumann U47
« Reply #3 on: November 11, 2014, 07:17:32 pm »

Hey guys. Thanks for your help. I just reversed the capsules so that the rear is attached to the cardioid pattern. Boom, it works. The noise was all coming from the front capsule, the audio is now super clean with both tubes.

This isn't great news as one of the capsules is a gonner (on inspection there is a large scratch on the front capsule, but at least I can use the mic in cardioid. Is it possible to turn the capsule saddle around if I unscrew the saddle from underneath? Or is that a dangerous thing to try on my own?

Thanks again!!
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klaus

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Re: Broken 1959 Neumann U47
« Reply #4 on: November 12, 2014, 12:42:38 am »

Have a qualified person reverse the capsule, not the mount. Trying to unscrew the capsule mount column to reverse front sides is a pain:  the mounting column is glued in place, in addition to being screwed down, and takes skills to dislodge without breaking the plastic base plate or the vulcanized rubber column base.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Uwe

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Re: Broken 1959 Neumann U47
« Reply #5 on: November 13, 2014, 05:41:30 pm »

Ask for  Martin Gathard at Sennheiser UK - he is the real expert on Neumann mics and has been working on them for over 30 years.
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klaus

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Re: Broken 1959 Neumann U47
« Reply #6 on: November 13, 2014, 05:52:07 pm »

Excellent referral. Thanks, Uwe.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

studiofocusrec

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Re: Broken 1959 Neumann U47
« Reply #7 on: November 20, 2014, 08:46:18 am »

Thank you once again for all your help. Very useful information! I think I'll get the mic sent off.
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