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故障现象:该机在通电后,电源指示灯瞬间闪亮随即熄灭,出现“三无”。分析检修:接通电源后,测量该机开关电源+B(115V)电压,发现其升至约40V 时即下降为0V。据此判断开关电源电路已启振,故障在保护电路的可能性较大。测量保护电路三极管 Q805 be 极间电压为正偏,表明保护电路已动作。焊下稳压二极管 D831(MA4100H,稳压值为10V),用万用表 R×1k 档
Symptom: The machine is powered on, the power indicator light flashing immediately extinguished, there “three no ”. Analysis and maintenance: After the power is turned on, the switch power supply + B (115V) voltage is measured and it is found to drop to 0V when it rises to about 40V. Accordingly, switching power supply circuit has been judged start-up, fault protection circuit is more likely. Measuring protection circuit Transistor Q805 be positive voltage between the poles, indicating that the protection circuit has been action. Welding voltage regulator diode D831 (MA4100H, regulated value of 10V), with a multimeter R × 1k file