This symptom on equipment that uses interconnection wires can sometimes be caused simply by one of the wires used becoming unattached, or one of them possibly touching something of a metallic nature somewhere along its route.
However depending on what form the buzzing is it could be a fault within the main device itself, so the only thing that can be done to verify exactly what applies is to take off pairs of wires at a time to be able to observe if any change in buzzing tone takes place, which would obviously happen if a defective pair was removed, if nothing alters then its an internal fault within the unit.
Although the above mentioned applies to all of these type of devices it would have been of assistance to have known what model is being referred to.
