It sounds like you have power to it, but I'd check that first. The hum is likely a transformer if it's a rather soft hum, (not a motor stick hum). I'd check the fuse on the board. It is probably a 3 amp car type fuse. If that is good, I'd check power to and from the transformer, (120v in 24v out). If all that is correct, then I'd be leaning towards the board being bad, but I can't really confirm that without being there.