DVD players use an intricate laser device to scan the surface of the DVD. The DVD disc itself is made up of many different ridges and valleys, far too small for the eye to see. The laser, however, picks them up and translates them into binary code used to construct image and sound. When a message appears that there is no disc in the player when there is, it indicates a problem with the disc, the laser, or the loading mechanism.
Check the Disc and Power Settings
Owners should always begin by checking the disc itself. Often, the problem is a small one: the disc may have been put in upside down. Sometimes, the disc is slightly out of alignment in the loading tray and needs to be repositioned. At other times, the disc may be too worn or dirty for the player to read properly. If the disc appears clean, then check the power settings. Ensure any power cords are plugged in and operating correctly. Check lights on the players to see if any are failing to light (showing an internal power problem) and test cables to see if the power cable feels loose or frayed.
Check Loading Mechanism
If the disc appears to be in good shape and the power connections appear stable, the problem may be with the loading mechanism itself. If the mechanism is not working properly, it may not shut all the way or move the disc properly into alignment with the laser. Owners should check to make sure the tray loads smoothly and that it clicks fully closed. If the tray is broken, the player may need to be replaced.
Clean the Lens
If the loading tray is working properly, then the lens that directs the laser may have problems. If owners have a cleaning DVD, they can insert it and run it. If this doesn't work, they can attempt to clean the lens themselves with a delicate cloth, but this requires taking apart the front of the DVD player and can be a delicate operation.
Check Servo Alignment
The servo and related devices are what controls the spin of the DVD. If the servo is misaligned or not working correctly, then it may not register the disc or move it properly. This can cause the player to assume there is no working disc in the player. A servo can be replaced, but it may be easier to simply replace the entire player.