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[例1] 故障现象 插上电源插头,时钟显示正常,接通电源开关,电源指示灯亮,带盒插不进。 分析与检修 接通电源开关,电源指示灯亮,说明该机开关电源和定时器电路工作基本正常。对上述现象分析后初步判断故障出在主导轴电机驱动电路中。接通电源开关,用万用表检查主导轴电机驱动集成块IC1M③脚(V.CAPST),发现③脚电压仅有1.8V,而正常值为11.6V。拔下接插件PG144插头测量插座⑧脚电压为2.6V,说明故障出在主导轴电机驱动电压(V.CAPST)产生或控制电路中。检查电源输出接插件PG1各脚电压,发现④脚、⑥脚和(13)脚输出电压均为1.8V(正常值见接插件PG1各脚电压标值)。检查达林顿复合管Q5集电极无电压,进一步检查发现集成电路保护器PR4内部已开路,因此造成V.CAPST无输出,主导轴电机驱动集成块ICM不工作。集成电路保护器PR4/10P—N38外型象小型塑封三极管,这种特殊器件损坏后市场上很难买到,检修时可用一只
[Example 1] Symptom When the power plug is inserted, the clock is normal, the power switch is turned on, the power indicator is on, and the cassette is not inserted. Analysis and maintenance Turn on the power switch, power indicator light, indicating that the machine switching power supply and timer circuit work is normal. After the above analysis of the phenomenon of the initial judge fault in the lead-axis motor drive circuit. Turn on the power switch, with a multimeter to check the main shaft motor drive manifold IC1M ③ feet (V. CAPST) and found that ③ pin voltage is only 1.8V, while the normal value of 11.6V. Unplug the connector PG144 plug measuring socket ⑧ foot voltage of 2.6V, indicating that the fault is in the capstan motor drive voltage (V. CAPST) generated or control circuit. Check the power output connector PG1 voltage of each pin and found ④ feet, ⑥ feet and (13) pin output voltage is 1.8V (normal value see the connector PG1 pin voltage standard). Check Darlington composite tube Q5 collector voltage, further inspection found that the internal circuit breaker PR4 has been open, resulting in V. CAPST no output, the capstan motor drive ICM does not work. Integrated circuit protector PR4 / 10P-N38 looks like a small plastic molded transistor, this special device is difficult to buy on the market after damage, can be used when the maintenance of a