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故障现象:插入电源线,显示屏无显示,电源开关打不开,整机不工作。分析与检修:显示屏无显示,整机不工作,引起故障的原因:(1)电源工作不正常。(2)微处理器工作不正常。录像机插上电源后,不论电源开关是否打开,显示屏应有[0:00]闪烁显示。显示屏无显示,引起故障的原因:(1)无供给显示屏的-30V驱动电压。(2)微处理器工作不正常。(3)无供给显示屏交流灯丝电压。(4)显示屏坏。首先测IC(56)脚有-30V电压,再测微处理器IC_(601)①脚5V供电电压约为0.5V左右。原来是微处理器工作电压太低,造成显试屏无显示,整机不工作。为判定是5V供电电路有问题,还是IC_(601)有问题,下一步检查5V供电电路。5V供电电路由IC_(801)⑥脚输出12.2V电压经三极管Q_(601)稳压后,由发射极输出5V电压,经L_(601)、L_(602)加到IC_(601)第一脚。电路如图1所示。测Q_(601)集电极和IC_(801)⑧脚电压都为1V左右,比
Symptom: Insert the power cord, the display no display, the power switch can not be opened, the machine does not work. Analysis and Maintenance: No display screen, the machine does not work, cause of the malfunction: (1) power is not working properly. (2) The microprocessor is not working properly. When the VTR is plugged in, the display should flash with [0:00] regardless of whether the power switch is turned on. Display no display, the cause of the malfunction: (1) -30V drive voltage is not supplied to the display. (2) The microprocessor is not working properly. (3) No supply screen to exchange filament voltage. (4) display is bad. First test IC (56) feet -30V voltage, then test microprocessor IC_ (601) 1 foot 5V supply voltage is about 0.5V or so. The original microprocessor operating voltage is too low, resulting in significant test screen no display, the machine does not work. To determine if there is a problem with the 5V supply circuit or if there is a problem with IC_ (601), check the 5V supply circuit next. 5V supply circuit by the IC_ (801) ⑥ pin output 12.2V voltage regulator by the transistor Q_ (601), the output voltage 5V by the emitter, the L_ (601), L_ . Circuit shown in Figure 1. Measure Q_ (601) collector and IC_ (801) ⑧ foot voltage is about 1V, than