Neumann TLM 49 mic buz when touching body

[JRE Productions]

Just bought a used TLM49. Its very quiet and the sounds works for my voice.

I noticed when messing with the position of it on the stand, if I touch the body of the mic I get a bit of ground hum. The hum is extremely low in volume, but I can hear it. As soon as I let the body of the mic go, it disappears. No noise at any other time even with the gain cranked.

I did a quick check with my other condenser mics (AT 4047 and MXL 603s) and none of them behave the same, so I am assume the cable is good (although the AT4047 is transformer based and may be isolated).

Thoughts?
Joe

 

[emrr]

Various mics I have all buzz when touched.  Maybe 25%.  SM57 amongst the worst. 

 

[JRE Productions]

Ok in typical DIY fashion of troubleshooting:

*I check all the cables I had with the same results (not cables)
*Removed the XLR patch bay and connected direct to preamp with same results (not patch bay)
*Tested using the pres from the interface with same results (not pre amp )
*Hum is louder when touching the head shell and gets less noticeable the further away from the shell.

So I removed the head shell and inspected.  The only  thing that looks a bit disturbed or disappointing  is the black wire from the diaphragm. The yellow wire that energizes the diaphragm has a nice clean solder joint that is barely larger than the wire attached. The black wire looks more like a solder blob at both ends. I wiggled a little to see if any movement. Seemed solid.  Maybe a cold solder joint? Maybe not. BUT.. when I reassembled everything is completely quiet. No hum. Not sure if it was the black wire that I moved or if removing and reinstalling the shell made good ground contact. It was poorly packed and I am sure took some abuse during shipping.

I will use as is for now as it’s in my home studio. If it starts having hum issues again when being touched, I will touch up those solder joints.

 

[emrr]

It's almost always about the external shielding.  I have an Oktava LDC head that gets noisy, loosening and tightening the case cures it. 

 

[bremusound]

Check your cable, sometimes connecting or disconnecting pin 1 (GND) to the XLR housing makes a difference.

 

[JRE Productions]

Decided to take it apart again and resolder the black lead. So for sure it was removed and resolder. The Neumann factory wiring has this lead slipped in a tube and soldered. Whoever was inside this mic solder the black wire to the side of the tube with a blob. Similar at the other end where it connects to the wire tab that screws into the diaphragm.  No clue why this was removed and soldered incorrectly.  But it’s nice and tidy and sounds as it should.  Everything else seems correct inside.

Thanks for your help.