I just bought a KRK Rokit RP6 G2 from ebay and before I return it as "not working" and have to spend another several weeks searching to buy another, please help me try and fix this.

The monitor's light turns on when plugged in and switched on, however no matter what I try, I can't get it to play any music from the TRS input (not specifically just this input though). Weirdly it may make some static noise on the odd occasion, but other than that it just won't work. The power supply also buzzes quite loudly when the back panel is taken off and the monitor still switched on.

Pleease help, and thanks in advance :??: