Akg P420 grouploop promblem

[yuaylooper]

Brother , what the screw ? i need to tight it ? Or cleaning the colour on it to stop groundloop promblem . I’m fear to do . Somebody please help me to comfirm . I dont understand the Fix with text

 

[yuaylooper]

promblem gone when i touch it’ hard but some time i move a mic or remove fromstand . Issue have come TT

 

[micolas]

On my black P420, with fine sandpaper I cleaned the paint a little in some places, for a better electrical contact, I tightened the nut well and the hum disappeared