Lasers will typically "fall off" in output as they age. As such, their ability to recover data also declines as they age. Whereas some "scuffed" discs may play fine in a new machine with a new, high output laser mechanism, the older laser with lower output is more easily "confused" and can't read the disc quite as well. One might consider this akin to "reduced mental capacity" as one gets way up in the years : )
In many cases, there are adjustments in the player that allows one to "tweak" a laser back into spec. If one has to resort to doing this, you can bet that the laser is getting weak and may need replacement sometime shortly. "Shortly" might be two weeks or it might be two years, depending on how far out of whack it was to begin with and how often you use the player.
If you've got a really old player that you absolutely love, you can have the laser replaced. Depending on the machine and where you have it done at, this should run somewhere around $50 - $125 for the laser. This does not include about 1 - 1.5 hours worth of labor to remove the old one, replace it with the new one & calibrate it for proper operation. As such, you could end up with $125 - $300 invested in reviving your "beloved". Since CD technology ( especially in the DAC section and the filtering being used ) really HAS gotten much better as time progresses, doing such may not be such a good move unless the player really is quite special to you.
The only time that i would recommend replacing the laser with no hesitation would be if one were using a high end transport and the laser failed. Since most of the performance improvements have been in the areas of filtering and DAC's, the transport can still do its' job quite well and you can upgrade the DAC as deemed appropriate. Sean
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