Fault phenomenon caused by damage of the most flam

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The fault phenomenon caused by the damage of the laser head

1, the disc does not rotate

usually appears the word "no disc" on the display screen. The reason is that the laser diode is aging, the laser head is dirty (including the objective lens and the internal optical lens), the objective lens or photosensitive detector is damaged, and the focusing coil is open or soldered

2. Pick up discs

high quality CD and VCD discs can be played. If the quality is slightly poor, zigzag tests are often used in production to evaluate the zigzag strength and plastic deformation of materials. It is difficult to read or even cannot read discs. The reason is that the laser head is slightly dirty, which weakens the laser power emitted by the laser diode, the grating of the laser head is slightly offset, or the laser diode is slightly aged

3. Difficult or inaccurate selection of music

after a long time of reading the disc, you can choose the track to play, or you can't choose the specified track. The main reasons are that the objective lens is dirty and damaged, the aggregation coil support is slightly inclined, the grating is shifted, the performance of the photosensitive detector is unstable, and the inclination angle of the laser head is misadjusted

4. The TOC display screen cannot display the total playing time, total number of tracks and other contents of the disc. The reasons are that the tracking coil support is tilted, the light fake and flame-retardant B1 polyurethane products fly all over the sky, the grating is shifted, the laser head is dirty, the optical components are loose and shifted, and the laser is removed, for example? Br 5. Disc skipping or playback pause

when disc skipping, the sound "jumps and sings", and the image is broken and incoherent. When jumping the disc, the image freeze, mosaic phenomenon appears, and the sound repeats constantly. The reason is that the grating shifts and the laser power decreases

maintenance of laser diode

the laser diode is the light source generating device of the laser head. After it is aged or damaged, the laser emitted will become weak, making it difficult for the laser head to get the focusing and tracking signals, resulting in the failure of the disc to rotate or the inability to read the data in the directory area. There are four methods to judge whether the laser diode is good or bad:

1. Measure the laser power

use the laser power meter to measure the laser power emitted by the laser diode. Normally, it should be 0.13-0.3mw. If the measured laser power is significantly reduced, and it cannot be raised to the normal value by adjusting the laser power trimmer potentiometer, it can be concluded that the laser diode is aging

2. Measure the driving current of the laser diode

when the RF signal is equal to or greater than 1.5vp-p, and make it move in a magnetic field with uniform gradient, the driving current should be less than 120mA. If it is greater than this value, it indicates that the laser diode is aging

3. Measure the radio frequency (RF) signal

if the RF signal is less than 1.5vp-p, adjusting the laser power fine-tuning potentiometer cannot raise it, indicating that the laser diode is aging

4. Measure the resistance of the laser diode

under normal circumstances, its forward resistance is 15-25kw, and its reverse resistance is infinite. If the forward resistance is greater than 60kW, it indicates that the laser diode has been damaged. The laser diode can be replaced after it is damaged. Due to the deviation of the light source center of each laser diode, the light point of the three beams emitted to the photosensitive detector deviates from the central position of the receiving unit. Therefore, after replacing the laser diode, the position of the cylindrical lens must be adjusted, and then the grating fine adjustment must be made to make the light point of the three beams accurately fall on the central position of the photosensitive detector of the barefoot scaffold fastener safety testing machine, which fully meets the experimental requirements of gb15831 (2) 006. This adjustment process is very delicate, and we should be patient and repeated

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