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Author Topic: Broken U87 head contacts-what to do?  (Read 1061 times)

RuudNL

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Broken U87 head contacts-what to do?
« on: July 06, 2019, 03:24:00 pm »

I have a Neumann U87 with some damaged contacts in the microphone body.
It seems that someone has removed the capsule assembly and placed it back while the pins of the capsule head were not properly aligned.
So I would like to replace the contacts, but the problem is where to find the correct type.
I know that Neumann used to sell the whole socket assembly, but it goes a bit far to order a complete new one, because only a couple (2 or 3) of the small contacts are damaged.
So: where could I find usable (female) contacts, that would fit the plastic base?
Eventually I could use contacts from a cable connector that would take the same pin size (1.5 mm if I remember correctly). Any help would be highly appreciated!
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klaus

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Re: U87 (female) contacts for the capsule assembly
« Reply #1 on: July 06, 2019, 05:35:37 pm »

You gave the hint for the solution in your last sentence: simply* extract one from a Tuchel broadcast connector, and install it in the mic! The contacts used in U87/U67 head assemblies are actually the same as used in Tuchel-brand broadcast mic cable connector females.

* You need to use a trick to extract the pin from the connector without damaging its anchor: push the little barb/anchor which blocks the pin from coming out of its position inside the plastic connector IN, i.e. towards the center, as you lift it out. Use a very small screwdriver blade to do this:  ≤ 1.2 mm. Once out, reestablish the angle of the barb, so it again will seat properly in the Neumann head without being pulled out when removing the capsule head
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Klaus Heyne
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RuudNL

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Re: U87 (female) contacts for the capsule assembly
« Reply #2 on: July 07, 2019, 03:28:50 am »

Thanks Klaus! That is a great and simple solution.
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RuudNL

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Re: U87 (female) contacts for the capsule assembly
« Reply #3 on: January 11, 2020, 09:53:26 am »

Some time ago I had another problem: a U87 with broken pins from the capsule head assembly.
Although it may sound like a rather crude solution(!), I used 1.5 mm thick brass nails...
I did cut the nail to length, rounded the end (like the other pins) and used the head of the nail to solder on.
Then I glued the nail in place with two component epoxy cement.
If you don't know what was replaced, you can't see the difference with the other (existing) pins.
And yes, of course there is a difference between gold and brass, but the microphone has worked without any problems since the 'repair'!
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klaus

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Re: U87 (female) contacts for the capsule assembly
« Reply #4 on: January 11, 2020, 02:53:16 pm »

Another way to replace a broken head pin (this only applies to U87Ai): transplant the ground pin (#7) to the position that's broken:
with careful application of heat to the pin, you can pull it out of the slightly melted plastic and, applying some epoxy, you can seat the transplanted pin in its new position.
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Klaus Heyne
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RuudNL

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Re: U87 (female) contacts for the capsule assembly
« Reply #5 on: January 12, 2020, 05:39:10 am »

Yes, I've read about that solution before, but I like to keep the microphone body and capsule head compatible, so you can exchange parts.
I am sure that some people will say that brass will become oxidized after some time, but as long as you use the microphone in a dry environment, I don't think this is a real problem.
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klaus

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Re: U87 (female) contacts for the capsule assembly
« Reply #6 on: January 12, 2020, 02:31:22 pm »

The problem with unplated brass as electrical conduit to a plated contact (silver-plated female in the head section of the mic) is its propensity for accelerated oxidization due to current transfer across dissimilar metals.
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Klaus Heyne
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RuudNL

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Re: U87 (female) contacts for the capsule assembly
« Reply #7 on: January 12, 2020, 03:25:44 pm »

Well, time will tell!...
But: isn't there the same 'problem' with with silver-plated female contacts and gold plated pins?
As long as there is no high humidity (and high humidity is the last thing we want with condenser microphones!), I suppose the oxidation problem will not cause any problems for a long time.
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klaus

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Re: U87 (female) contacts for the capsule assembly
« Reply #8 on: January 12, 2020, 05:10:02 pm »

But: isn't there the same 'problem' with with silver-plated female contacts and gold plated pins?

Yes, there is, and conscientious studio owners, engineers and technicians try not to mate dissimilar metals in their cable connections for that very reason.
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Klaus Heyne
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Jim Williams

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Re: Broken U87 head contacts-what to do?
« Reply #9 on: January 13, 2020, 11:20:38 am »

Mating of dissimilar metals causes what is known as "metal migration". Alloys break down and dissimilar metals will cause that effect. Electrically it causes a diode effect with electrons snapping across those barriers. Yes, it is another form of distortion.

Stabilant 22 was designed to lessen those effects but that liquid brings its own issues to the table as it will dry out and attract contaminants.
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