Unit will not acknowledge presence of disc.

Initally got the "No Disc" message on panel on all discs, including standard and -R, I try to play. Problem continued. Weeks later, when I tried to open the tray, I heard whiring noise inside box and tray would not open. Since I have had the tray problem before on another P1440, I suspect the belt the opens the drawer has snapped. I can fix the later, since I have some spare belts of the right size. But I still need an answer to the "No disc" problem. I might add that before the drawer opening problem started up, I did open the box and it appeared to me that the panel containing the LED/sensor did move into position properly when the door (which worked then) slid closed.