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First of alll try to reset your unit.Unplug everything all the wires and cables connected to it, waiting 15 mins, and then plugging it back together.Hope it works,if not then,
The drive is not reading the disk properly. This is either caused by a fault in the laser/lens/drive itself which is leaving the laser misaligned and unable to read the disk or it is caused by dirt in the drive effecting the lens.
There is a Laser cleaning CD or DVD that you can purchase from any audio shop - its not expensive and useful to have around anyway. I would recommend you try a good qulity one such as this from Maxell http://www.amazon.co.uk/Maxell-Europe-Ltd-CD340-Cleaner/dp/B000001OM5
You may find that this will resolve the problem as a simple and quick fix.
If the cleaning disk does not work then you have to go mannualy,You should be little handy with electronics item.
1. Remove the screws that hold the top case on the dvd player. There will be a couple of screws on each side of the player and a couple of smaller screws on the back.
2. Once the cover is removed, take the can of compressed air and blow out the entire inside of the case. Make sure to blow inside the carriage and around any moving parts of the dvd player including tracks, tray, gears, etc.
5. Check the inside of the carriage using a small flashlight and look closely to make sure there is not debris caught in the spindle or other places like hair, large clumps of dust, dirt, and anything else that should not be there. If you see this kind of material remove it with tweezers and repeat blowing out the inside.
6. Pour a small amount of the rubbing alcohol into the cap and lightly dip a cu-tip in it and shake off any excess.
7. Now and clean off the optical lens (which will look like a small glass bubble in the middle of the carriage) with the cu-tip. Repeat this process a couple of times using a clean cu-tip each time.
8. Let air dry for 2 minutes before plugging the player back in and closing the tray.
Carefully see what the door is caught on or the gear, remove whatever debris might be there( hair, dust, etc) use q-tips and toothpicks.Clean all the parts and it will work
9. Replace the cover and clean your discs before placing them back in the player. Test to see if the problem has been fixed.
This is a picture of the optical reader and spindle/spindle motor assembly. You can see the optical reader lens (looks like a small round glass bubble) in the middle and this is what you need to clean. In some models, the optical assembly will be covered and will not be open for easy access.but still can be cleaned.
It will solve your problem or else you have to go for the service repair.Playing for a period of time, the lens has weaken so the lens has to be replaced.
It can be done in any electronics repair shop.First quote for the cost of repair.
Hope it helps.It would be kind enough if you please remember to click the green ACCEPT button.