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例1故障现象:接通电源开关,电源指示灯不亮,带盒不进仓。分析检修:闭合电源开关,电源指示灯不亮,先用万用表检查稳压电源输出的13V、9V和5V电压,发现除13V电压正常外其它电压均为0V,估计故障在系统控制或稳压电源电路中。用万用表检查系统控制微处理器IC1第(44)脚(电源控制)为低电子0V,接通电源开关,第(44)脚仍为低电子0V(正常值应为高电平5V)。检查IC1第(52)脚(VCC)无电压,由此确定故障在5V稳压电源电路中,该电路如图1所示。检查调整管Q1集电极13V电压正常,检查基极和发射极电压为0V。进一步检查稳压管ZD1已击穿短路,因此造成+5V电压无输出,微处理器IC1不工作,于是出现上述故障。更换稳压管ZD1/5.6V后,机
Example 1 Symptom: Turn on the power switch, the power light does not shine, with the box does not enter the warehouse. Analysis and Maintenance: Close the power switch, the power light is not lit, first check the power supply with a multimeter output voltage of 13V, 9V and 5V and found that in addition to the normal voltage 13V voltage are 0V, estimated fault in the system control or power supply Circuit. Use a multimeter to check the system control microprocessor IC1 (44) pin (power control) is low electronic 0V, the power switch is turned on, the (44) feet are still low electronic 0V (normal should be high 5V). Check IC1 (52) feet no voltage (VCC), thus determine the fault in the 5V power supply circuit, the circuit shown in Figure 1. Check the adjustment tube Q1 collector 13V voltage is normal, check the base and emitter voltage is 0V. Further check the regulator ZD1 has breakdown short-circuit, resulting in no output voltage of 5V, the microprocessor IC1 does not work, so the above failure occurs. After replacing the regulator ZD1 / 5.6V, the machine