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In Reply to: RE: Problems Reading CD posted by firstname.lastname@example.org on May 22, 2017 at 21:34:29
This seems pretty normal to me. Laser diodes do not last forever. Or more accurately they will not put out the same amount of optical power over time for a constant input current.
As they age they put out less optical power and require a higher current to maintain consistency. Obviously this cannot go on infinitely.
Other factors can affect the rapidity of ageing like power surges, heat and humidity.
As far as I can establish an average laser diode life is difficult to ascertain but a maximum life appears to be around 9 - 10,000 hours of use. Of course some fail earlier and a few that prove the rule may go on for a bit longer. Of course you will read of people who say that they have a CD player from the year dot which still plays perfectly. I have one myself dating from around 1987. What I am not telling you is that I rarely switch it on and it was last in regular use twenty years ago. Similar caveats apply to some of these "everlasting" player reports. In addition reports of very long laser diode life ( 50,000 hors) seem to relate to laboratory tests in perfect conditions where the laser system does not suffer the slings and arrows of outrageous fortune met in a domestic setting.
Your player may be around 14 years old. So it's time to move on I suspect. You have had them fail before and I guarantee that whatever you buy as a replacement will also fail at some point in the future.
Optical drives are getting rarer and may not be available in the mid to long term. One of the reasons many are swapping to computer files for music and movie replay.
In regard to CDRs, they are harder to read ( require more power) than pressed CDs. Also the dye used to form the optical record may deteriorate. Reading old CDRs with an old laser has a very good chance of being unsuccesful.
PAR is correct that laser diodes (like all light sources - even the sun) have a finite lifetime. All modern units have a light intensity sensor that adjusts the laser drive current to compensate for diminishing power over time. (Both LEDs and laser diodes fail very gradually, unlike incandescent bulb which fail suddenly.)
However there is another variable and that is the light path. The output from the laser diode first hits a prism so that the beam is reflected up onto the disc. The height of the bumps in the disc is 1/4 the laser wavelength so that when the beam hits an area with a bump that the reflected light cancels with the part of the beam illuminating the flat surface around the bump. This reflected beam travels back through the prism to strike the photodiodes, which sense the signal level.
Often the problem is that the various lenses, prisms, beam splitters, and mirrors will become dirty (especially if in the house of a smoker) and thereby reduce the total light power striking the sensors. Only one lens is easily accessed, but cleaning this one often cures the problem. One can either clean that lens with a cleaning disc played in place of a CD. The spinning disc has soft brushes on the bottom that clean the lens. If this fails, one can unplug the unit from AC power, remove the cover, remove the bridge over the loading tray and clean the lens with a Q-Tip (cotton swab). Much more work, but much less expensive. Good luck!
Charles, many thanks and, yes, cleaning the collimator lens (the accessible part) can do the trick in some cases. I considered offering this advice. However my experience is that although this action may be fine with a soiled but otherwise good and serviceable OPU, with a 14 year old unit that has been used regularly any gain will inevitably be short lived.
The unit was purchased a few years ago from a person who used it only a few hours before putting it back in the original packing. So I purchased an almost new unit that I've used moderately heavily since I bought it.
That is encouraging. I had to assume that the unit was regularly in use since the model was introduced in 2003.
Of course those "few years ago" may be longer ago than you think ( time goes by so quickly) and I hope that the previous owner wasn't like a used car dealer where each vehicle was owned by a little old lady who only used it to drive to church on Sundays :-).
Anyway good luck with the cleaning. Just be careful how you do it. If you can, use a good pro photographer's lens cleaner fluid sparingly with pro lens cleaner tissues (careful use of a Q tip otherwise). if you can't get to the lens and have to insert a cleaning disc try to avoid the type with small sponges which you dampen with a fluid which are stuck to a CD . That type has the potential to knock the lens off its mounting. The other type (if still available) has a small spiral of carbon fibres. Less potential for damage but not great for removing oily deposits though OK for dust.
The manufacturuer of my own disc transport recommends the use of a "canned air" type of aerosol to deal with dust. That has the advantage of no physical contact and may not require opening up the machine.
Meanwhile I have no knowledge of any method for rejuvenating CDRs where the dye may be deteriorating, this being another possible element of your problem. They are just not suitable for the long term storage of data.
I'll give it a try. Thank you.
Thanks. I hoped for better but even when the answer is not what one wants, knowing what's going on is still better than not knowing any reason. And it means I don't waste my time trying to find a fix.
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