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例1 故障现象:插上电源插头时钟无显示,按下电源开关,电源指示灯亮,插入带盒按各操作键均不起作用,按“VTR/TV”键,VTR指示灯也不亮,按出盒键带盒弹不出。分析与检修:由上述故障现象分析,初步判断故障在定时器操作或控制电路中。打开机壳,在停止状态时用500型万用表检查IC7501(MN14824VTU)各脚对地电压,发现(13)～(16)脚(数据输出)电压均为0 V(正常值应为4.8 V),检查(17)～(20)脚(定时器数据)均为高电
Example 1 Symptom: There is no clock on the power plug, press the power switch, the power indicator light is on, and the operation of the tape cassette is not effective. Press the “VTR / TV” button and the VTR indicator is off , Press the key box can not eject the box. Analysis and Maintenance: Analysis of the above symptoms, the initial judge fault in the timer operation or control circuit. Open the case, check the ground voltage of each foot of IC7501 (MN14824VTU) with a 500 multimeter in the stop state, and find that the voltages of (13) ~ (16) feet (data output) are 0 V (normal value should be 4.8 V) Check (17) ~ (20) feet (timer data) are high