Gemsound EXA-3955 Right Channel Problem

Question

Hey guys. I just bought a new Gemsound EXA-3955 amplifier and first time out of the box i plug it in and turn it on, and it works great. I dont turn it up too loud or change any wiring. Then I turn it on to show my friend the next day and the right channel wont work, and all i hear on that side is a low hum. Can anyone help me fix this problem. I checked all the wires and connections and they are all fine. Please help!