strange aerial?

am working on a fender passport p150 stereo mini pa system which fender wont service because it is out of warranty. fender never intended to fix this item cause it took me 2 hrs to take appart and all the connectors are glued on. in takeing this appart i came accross a screened cable coming out of the screened box which contains the electronics ( i have a shorted output transistor and shorted positive supply and the switch mode power supply keeps on trying to start giving a fart in the speaker of the channel which is still working) anyway its a cert ive got blown output transistors on at least one side but the thing is what is this screened cable coming out of the box and connected to a piece of wire which sits encapsulated in plastic inside the handle of the mixer unit. are we supposed to believe it senses the electromagnetic field of the room and performs some kind of subraction from the output for hum cancelling- or is it a tamper proof device to check for voided warranty - any guesses? - unit is out of warranty and fender refused to service it anyway!