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例1:故障现象:按下电源开关后指示灯亮,但遥控开机无光栅、无伴音。 分析检修:测开关电源+115V电压只有40V,+24V输出端电压仅为7.5V,且主板电源部分有“吱吱”声。断开电阻R444,在+115V端接上200W灯泡作假负载,开机观察灯泡微红且闪烁,由此判断开关电源有故障,应重点检查其稳压电路。经检查发现误差稳压放大集成块VQ827的②脚电压只有0.8V(正常值应在100V左右),故怀疑可能是
Example 1: Symptom: After pressing the power switch indicator light, but the remote boot without grating, no sound. Analysis and maintenance: measured switching power supply + 115V voltage only 40V, +24 V output voltage is only 7.5V, and the motherboard power supply part of the “creak” sound. Disconnect the resistor R444, connect the 200W bulb at + 115V to make a false load, turn on the observing light bulb and flashing red, so as to judge the switching power supply is faulty, we should check the voltage regulator circuit. The inspection found that the error voltage regulator amplification block VQ827 ② foot voltage is only 0.8V (normal value should be about 100V), it may be suspected