Black wire on capsule of old SM57

sile2001

sile2001

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Trying to help out a bandmate by fixing an older Shure Unidyne III SM57 he just bought off of ebay. It has 3 wires coming off the capsule that go down into the body of the mic: white, yellow and black. The white and yellow are soldered to connections down in the body, but the black wire is loose and looks like it pulled loose from a solder joint. There is another black wire down in the mic body that is soldered onto something of a crossbar. Is that where the black wire from the capsule is supposed to go?

If this doesn't make sense, I can post some pics later. I just thought someone might know right off what I'm talking about.
 
Nevermind, I just found the answer on another forum. The ground lead had been pulled loose from that copper bar inside.

This leads me to another question. Why does the capsule from one of my newer SM57's NOT have a ground lead?
 
On the newer SM57's, the body of the mic itself acts as the ground. So, a third ground wire is not necessary.

Cheers,
Zach
 
If it is a center-tap from the tansformer, it makes the mic potentially sensitive to being damaged by phantom power. That's why modern mics don't have them. I'd leave it unhooked.
 
The center tap was used as a signal ground. Whether or not this wire is a center-tap or not, I don't know enough about old Shures to say, I just wanted to toss a caution out there. Probably worth another question to someone who knows, or even Shure. Maybe someone else will chime in.
 
I just replaced one of these Saturday, so I've got the schematic in front of me. It shows that the black center wire coming off of the capsule is a ground. On some older models this wire will connect directly to pin 1 of the XLR. On newer models with only two wires on the transformer, the wire is not used, and the capsule is grounded through the chassie of the mic.

Cheers,
Zach
 
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