"NO DISC" DISPLAY TO DISC PLAYERS - 1

       This is a common fault occur to most of the Disc Players, irrespective of brand and model.

   The fault can occur to more than one reason.  The most common among them is with the optical pickup units' fault itself.  But before make sure, some more checks should be done. 
If by any means, the disc is not properly engaged to its reading unit, no disc display will be the result.  Thie fault will be mainly to its disc loading mechanism itself.  When we eject the player, a tray, called loading tray will come out to recieve the disc.  When we put a disc into it, and press play button, the disc will go inside, and will engage to the reading mechanism by means of a magentic catcher, and the tray which the disc has been carried in will isolate from the disc, and the disc must rotate.  If the disc won't engage properly to the magnetic catcher, it won't rotate.  Before going further, we have to understand what happens when a disc is isterted in to the mechanism.

    During burunig of disc, there are some signals burned to disc along with the picture, songs, or what ever be.  You may have noticed that, after burning all data, to disc, the burning software will display that it is recording some other signals to it.  You can notice that it is burning [Lead in Lead out] data to it.  This will be displayed for some time, say, at about half a minute, before the display "burinig is completed sucessfully".  What is this lead in lead out data.  This is a standard data, which will be burned to all discs, and is used to identify the disc by the player.  This data will contain all details of the burned data, length of the burned subject, start and end of each sections or folders, starting point, end point and so on. 

    When we insert a burned disc into any player, the player will read this lead in lead out data first [we can say it as registry].  This data will be prossesed in the processor section of the main circuit board of the player, and will stored in its memory, so that it can be retrived from there, as and when it needs.  As soon as we insert the disc into player, it engages well onto the magnetic catcher, the optical pickup lens will start focussing the reflective surface, a reflective beam will go into the optical unit back through the same way from where the incident laser beam has came from.  This first reflected signal will be sensed by the main circuit board, and it understands that there is a disc engaged into the mechanism.  A turn on signal will be given to the sled motor control IC [sled motor is one which rotates the disc], and the IC will start supplying voltage to this sled motor, and the disc begin to spin. 

    If the disc won't get well engaged to the magnetic catcher, the optical pickup unit can't detect whether there is a disc or not. and it will display No Disc.

    After the disc has been detected, lead in-lead out registry track will be read by the optical pickupo unit, and you can notice the disc inserted will spin more faster than normal at this period.  After the lead in-lead out track has been read out, the optical pickup unit will slide through its rail, from extreme inner track to extreme outer track. During this time, the previously registered lead in-lead out signals will be processed, and compared with the burned signal on the disc.  If all are found OK, by the main system processor, the player will either hault for an external command, or starts to play the first track it has found during reading. 

    If the Disc is recorded as multisession, folders, etc:- the main processor do not know frm where to begin, and will hault the process, while the disc still rotates.  We have to give external command, either by the players' front panel control, or by the remote control to start play.  If the disc is burned as non-multisession, the player will start from the first track automatically.

    From above explanation, it is clear that, if a disc inserted won't engage properly into the magnetic catcher mechanism, the disc wont spin and the player will get confused, and a No Disc display will be the result.

    What you have to do in this sittuation is, unplug the unit from AC mains socket, and open its top cover.  Plug it into the AC power, switch ON the player, eject it, insert a disc into it, and press play button.  See whether the disc engages properly to the magnetic catcher inside, and start to spin.  If it has been engaged properly, and do not spin at all, make sure that, either the sled motor is faulty, or it do not get proper voltage from the main baord to spin.

    If disc do not engage properly to the magnetic catcher, the tension of the loading belt has gone down, or pulling power of loading motor, that pulls in the disc tray is very weak.  If just pull in the disc tray a little bit into the player make it engaged fully and disc start to spin, make sure one among the above stated might be the cause.

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