[Elecraft] K3: AC Hum on SSB problem

[Jay]

I brought my K3/100/P3 to our winter place this year instead of the old 
IC-735.  The K3 (with MH2 I use with the K2) also came along for 
convenience.  The problem is I'm getting hum on my signal.....Unless I 
maintain my finger on the mic socket (gnd).....Any finger works!  I've 
tried: Buying a new power supply, grounding rig to supply, grounding 
everything to a water pipe downstairs (I'm upstairs), doing the K3 mic 
plug ground mod, grounding the shield of the MH2 together with the mic 
ground all with no effect.  At the home QTH I don't use the Heil hand 
mic but two other mics (Heil) that I did not bring with me.  Also tried 
various settings of bias and mic/comp levels.  I can hear the hum in 
"test" mode, and everyone can hear it when I'm transmitting.  Any 
suggestions would be appreciated.   Jay, W6JDB