Whats wrong with my monitor?

[Osten Powers]

Hi all!
First I wanna excuse but I don't know where to post this question on gearslutz, so I posted it here!
I have a problem with one of my monitors (Event 20/20 bas). Recently the tweeter makes noise from time to time, sounds like you are searching a frequency on your radio! It comes and goes. Yesterday there was nothin, today I turned the monitor on and it makes noise again. The problem is definitly from the monitor, because the noise is there as well when there is no audio connection!!! I changed the power cable, put it in another jack...it's still there! I have the impression that the noise goes if the monitor is powered long enough! I turned the potentiometers on the backside of the monitor, but that's not the problem! Have any of you experienced something like that?

Thanx Osten Powers

[explorer]

Is there a mobile (cell) phone anywhere near the monitor speakers by any chance?

[Osten Powers]

Thx for the response! No there's is no mobile and it don't sounds like the inteference of a mobile phone. I plugged the power cable in different Jacks, but it seems to me like that's not the reason for the noise. Any other suggestions?