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例1 故障现象:无论是VCD及CD碟片均不能播放,显示屏显示“NO DISC”。分析与检修:先打开机器上盖,通电后发现激光头聚焦,寻迹动作正常,但仔细观察激光头无激光射出。因此估计激光二极管可能损坏,再用万用表测量激光二极管的正反向电阻值,结果为正向电阻14kΩ(正常),反向电阻值为无穷大,说明二极管没有损坏。继续测量驱动三极管WQ_2,发现该管c极在光头聚焦时只有0.6V,且毫无变化,于是拆下WQ_2检测,该管e极断
Example 1 Symptom: Both VCD and CD discs can not play, the display shows “NO DISC”. Analysis and Maintenance: First open the machine cover, power and found the laser head focus, tracing movements are normal, but carefully observe the laser head without laser shot. Therefore, it is estimated that the laser diode may be damaged, and then measure the positive and negative resistance of the laser diode with a multimeter. The result is a forward resistance of 14 kΩ (normal) and the reverse resistance is infinite, indicating that the diode is not damaged. Continue to measure the drive transistor WQ_2 and found that the tube c pole in the optical head focusing only 0.6V, and no change, so remove WQ_2 detection, the tube e extremely off