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一台F78—Ⅰ型300mAX线机,自80年底启用至今,在笔者修复的各种故障中,有五次属拍片不曝光。原因分析:该机拍片,是先按下手闸AN10作准备,而后松开手闸曝光(见图1)。为保障高压端元部件的安全;该机设有启动保护电路,它是不曝光故障的首查部位。该电路原理见图2a)。由于JD_6工作,这样为控制电路中摄影接触器JC_3或JC_2的工作提供条件(见图1)。JD_6动作的条件是稳压电源经R_(105)、R_(107)向C_(15)充电,使C_(15)两端电压超过BG_8发射极上的基准电压(WY11两端电压),BG_8、B
A F78-I 300mAX line machine has been in use since the end of the year 80. Among the various failures repaired by the author, there are five shots that are not exposed. Analysis of the reasons: The machine film, is to press the hand brake AN10 to prepare, and then release the hand brake exposure (see Figure 1). In order to ensure the safety of the high-voltage end components, the machine is provided with a start protection circuit, which is the first inspection site that does not expose the fault. The circuit principle is shown in Figure 2a). Since JD_6 operates, this provides conditions for the operation of the photographic contactor JC_3 or JC_2 in the control circuit (see FIG. 1 ). The condition of the JD_6 action is that the regulated power supply charges to C_(15) via R_(105), R_(107), so that the voltage across C_(15) exceeds the reference voltage on the emitter of B_G_8 (the voltage across WY11), BG_8, B