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PostPosted: Tue Feb 14, 2006 6:14 am 
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Mobo-fu Master
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Joined: Wed Nov 12, 2003 11:57 am
Posts: 20851
Location: 07438
Trouble reading a disk from your optical drive? It's laser lens inside may be dirty! This is a small assembly that rides on two rails, moving back and forth by a drive motor. The lens has an electro-magnetic activated "carriage" that moves the lens assembly up and down slightly, and allows it to focus properly on the reflective data layer in the disk.
All optical drives, including the CD-ROM, DVD readers and all writers, use this method. The beam is reflected back to a sensor, through the same lens. That lens has to be "squeaky-clean" in order that the emitted laser beam is not scattered, and reflects off more than its intended very narrow target.. less than 0.6 microns wide, with about 1.6 microns spacing between the tracks! If the beam is scattered on return to the sensor, then errors are generated, and the disk cannot be read. The disk's surface must also be clean, as finger-prints can leave oily "fog" on the surface.
Even in a home where no one smokes, there can be a lot of cooking oils in the air, and other air-borne contaminants and dust. A cleaning occasionally with one of the disks for the cleaning of the lens is recommended. They are not expensive, and do a good job. Otherwise, you will have to dismember the optical drive, and manually clean the lens with a dampened cotton swab, using no stronger than mild dish soap and plain water. Never use any compounds that contain ammonia, as the lens will turn yellowish from its effects. Don't apply any liquids to the glued-on brush of the cleaning disk, other than what is supplied.. other than dampening with plain water.

If you have problems with burning a disk using certain brands, it may be that the reflective data layer in the disk is not sufficient to reflect the track surface. Some disks are almost transparent, and are not a good choice. The opaque disks are much better in quality. Always stick with what has a good brand name, for the best results.

Be Warned!!
The laser beam is invisible to the eye, and can cause instant damage or blindness if viewed! Never operate the unit when its cover is removed, unless you are wearing IR-protective goggles!


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PostPosted: Tue Feb 14, 2006 11:00 am 
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Black Belt
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Joined: Wed Aug 13, 2003 2:57 pm
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Location: Yorkshire, UK
A further point that I must bring up is that down the shaft below this lens is a prism. By the inherently bad design of optical drives and indeed CD and DVD players. dust can make it's way past the lens and cover the prism. This, obviously will have the same effect as a dusty lens, but unless your adept with a soldering iron and can build a jig to ensure the lens returns to it's original position, you'll never get in to clean it.
Don't get me wrong, cleaning the lens will work say 4 out of five times. Which brings me to a question:-
Who designed them in such a way, surely they would be better placed above the disc looking down?

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PostPosted: Wed Feb 15, 2006 8:49 am 
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Mobo-fu Master
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Joined: Wed Nov 12, 2003 11:57 am
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Right, Ripshod.. but if that entire design were inverted completely, it could be done. Yet the magnetic cap that holds the disk in place may not be secure enough, and the disk will lose its tenure on the platter drive rim. Skipping and data errors result! Otherwise, the drive bay would have to revert to the older full-height opening for such units. Most designs for laptops use a pressure-button on the spindle to lock the disk in place. Newer servo-motor designs allow a gradual speed-up of the disk, with more precise control of its spin. The prisim feature within the carriage was omitted for simplicity of intent. It is very difficult to clean that part of the assembly, and is best left alone. Alignment of the laser carriage parts is critical. No other maintenance aside from lens cleaning is recommended, save for a very light relube of the rails it rides on.


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