I've had this unit for many years with no problems at all. Recently the unit has been powering itself down or shutting off for no reason when trying to watch TV. If I power it back up after it shuts down it will stay on at times for several minutes and at other times for hours. My watching habits have not changed and I have not made any changes to the system. Any ideas as to what I can do to correct this issue or has the unit reached it time and I need to replace it? Any help would be greatly appreciated.