I have a 15 year old Nad Receiver 7155 and just stop sounding after i switched off and on again. usually i can hear the clicking sound of the relay before it sounds but this time its just none. the lights on the tuner receivers goes on but no sound coming out from the unit. I appreciate very much if you could furnish me with the schematic diagram. My wife and i and the kids love this unit very much. Your help will be greatly appreciated.