I've tried it on another board and now direct into the wall. Its still humming away - its not as loud as the last one, but there's definitely something going on. It also has a high pitched whistle when the screen is on, like an old CRT monitor or tv (or your ears ringing after a night out). I'm now trying to convince my partner we need to spend on a Rocky and she is trying to get me back on a 480. Could be luck of the production line.