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Recommendations for cleaning lasers in CD players. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Ham Radio Technologies
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This material is based on the experience of servicing Aiwa audio centers. The recommendations outlined here can also be used when repairing CD players from other manufacturers.
How does dirt get on the laser optics?
The CD player unit in the most common AIWA NSX-*** series of mini-systems is located in the upper part of the device, in close proximity to the ventilation openings. This makes the laser optics vulnerable to dust, which is carried in either from the outside by room air or by internal air currents.
Lasers really don't like smoking near the device - the resins contained in cigarette smoke settle on the optics and it is very difficult to remove them. And inquisitive cockroaches, for some unknown reason, love to climb inside the laser. If the cockroach is large, then it cannot turn around inside - it is crowded. And the cockroach does not know how to "reverse". The lack of food, the slowly frying laser beam do their job and soon the curious insect dies. And the player refuses to work.
Laser device
Before proceeding with the repair, let's look at a schematic laser device. Aiwa NSX mini system models use the following types of lasers manufactured by Sony: KSS-210, KSS-212, KSS-213.
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The laser in technical English is called pick-up assy.
This is a fairly complex device, consisting of a semiconductor laser (2), a special prism (4), a focusing lens with a correction mechanism (3) and a panel with photodiodes (1).
The laser beam (red arrow), reflected from the prism, passes through the focusing lens and falls on the disk (5). Reflected from the disk, the beam (green arrow) returns, passes through the prism and falls on the reading photodiodes.
As you can see, contamination of the lens or prism doubly impairs the passage of the beam, as it gets in its way twice.
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How to clean the laser?
Appearance of the laser (For example, KSS-210)
The "eye" of the focusing lens is clearly visible. The black surface around the lens is a plastic cap that protects the internal structure of the laser from external influences.
Contamination of the focusing lens is the most common and simplest malfunction. Dust is best blown off the lens surface. But, of course, don't just blow on it - by doing so, you will only pollute it even more. Professionals use special aerosol cans with compressed purified air. A spray can costs from 150 to 370 rubles, depending on the volume. You can buy it in specialized stores. In St. Petersburg, these are Mega-Electronics or AV-Center stores. Enough of such a can to clean a hundred or two lasers.
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A thin plastic tube extends from the head of the spray can, allowing you to direct air to the right place. To clean the laser, point the tube at the lens and "blow" on the laser for 1-2 seconds.
The lens surface can also be cleaned with a cotton swab. If the pollution is strong, then you can use ethyl alcohol. Do not press hard - this will erase the special anti-reflection layer on the lens surface. Yes, and the lens suspension mechanism is very delicate, pressing it can damage it.
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ATTENTION: in no case do not use acetone - the lens is made of plastic and you will hopelessly ruin it.
If cleaning the lens surface did not help, then dust probably got inside the laser, on the surface of the prism. This is a more complex pollution, but it can be dealt with. But for this you have to disassemble the laser.
After squeezing the tucks, remove the safety cap and you will see the following:
View of the laser with the cover removed.
A complex structure near the lens is a special electromagnetic suspension. It is part of the automatic beam focusing system. During playback, the electromagnet continuously corrects the position of the lens, keeping the distance between the lens and the disc constant. This is necessary because the disc rotates significantly in the vertical plane, and without the automatic focusing system, normal operation of the CD player would simply be impossible.
The first way to clean the prism: simple
Bring the tube to the gap between the lens and the housing and blow the prism several times in short bursts. It is impossible to blow for a long time, since the compressed air, leaving the cylinder, is cooled and, thus, the prism is also cooled. At the same time, condensation of moisture from room temperature air on the surface of the prism is possible. After the water droplets dry, dirt stains form, which will be very difficult to wash off.
This method allows you to clean the dust that has settled on the prism, but for more serious pollution, use the second method.
The second way: requiring accuracy
In the same way as in the first method, remove the plastic cover. Under it you can see two small screws. Mark thin lines on the metal frame through which the screws pass and on the metal base on the laser body. This will allow you to correctly install the lens in place during reassembly. And this is very important, otherwise the optical axis will be broken.
Unscrew the screws and remove the focusing lens. It is possible that glue drops will be applied next to the screws - carefully cut them off with a sharp scalpel.
View of the laser with the lens removed
In the shaft under the lens and there is a prism. It is necessary to gently wipe its surface. There is a slight complication here. The prism, as you remember, is at a 45-degree angle, and the usual cotton swab is too thick. It can only clear the center of the prism. To remove dust from the corners of the prism, a thinner tool is needed. Aiwa supplies service centers with special, smaller sticks.
On the left is a stick supplied by AIWA. On the right - a regular stick
At home, you can take a match, cut it off and wind a little cotton wool around the tip. The main thing is not to scratch the surface of the prism and make sure that there is no cotton wool left inside the laser. Wipe the prism with several strokes. Assemble the laser back, exactly matching the previously applied marks.
WARNING: Avoid sudden movements. The connecting cable between the electromagnets of the lens and the laser can be cut off by careless movement.
If, after carrying out the above operations, the CD player does not start working, then most likely either the laser can no longer be restored, or the malfunction lies elsewhere. If you want to get some explanations to the article or share your own experience - welcome to the forum.
In conclusion. One of the possible options for the failure of the laser is its overheating by ascending flows of warm air from the radiators of the amplifier elements and the power supply.
Publication: library.espec.ws
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