[sharpiel]

I have a couple of Robofocus 3.1 Hand Controllers and motors. I noticed when I plugged one of the hand controllers in last night that both motors emit a high frequency low volume "squeal". I swapped motors and cable between the hand controller units and the cause appears to be isolated to one of the hand controller units only.

Has anyone else experienced this and have and idea what I can do to stop the noise from occurring. Whilst low volume it would definitely be annoyingly audible on quiet nights..