Neumann u67 buzzing

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Joined
Apr 24, 2013
Messages
9
Location
NYC
I have a vintage u67 that is making a faint ground hum.

Here is what I observed:

The buzz follows the PSU (Checked with another known good mic, and checked the mic with another known good PSU)
Audio ground checks fine with a Fluke on both I/O connectors on PSU
Power ground checks fine with a Fluke against the chasis on PSU
When pad switch on mic is touched with a finger, the buzz/hum gets much worse

I looked inside the power supply and checked for dropped wires. Everything looks intact.

The supply was recently recapped by Tom Onofrio. I may just email him about it.

Any ideas what the problem could be?  I would blame the cable, but it checks good with the same mic, but different PSU.

Thanks y'all!

-Squarey
 
If you just had someone work on the supply, surely you should go back to him first? Please note, saying ' I have xx which hums, what is the problem?' is equivalent to saying 'I have a car, it doesn't go, whats wrong with it?' There are as many likely problems as there are parts in the unit.
 
Just looking for any troubleshooting suggestions really.

The tech is in another state,  and it would be great to avoid shipping it off if I can help it.
 
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