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上期我们介绍了系统控制电路的基本原理及故障检修概要,本期分析系统控制电路的几个维修实例。例1 机型:日立VT-M747E(DH) 故障现象:插上电源后显示屏无显示,按电源(操作)键指示灯不亮,其余按键亦全部失效,带盒插不进。分析与检修:这种故障通常发生在电源电路或系统控制部分(见图l)。对日立M747机来讲,由于采用开夫电源,机内各工作电压均由开关电源变换而得到,因而可在检修前先观察显示屏灯丝是否点亮,若亮,大体表明开关电源工作正常,否则说明故障在电源部分。如果监视(电视)机屏幕显示为白净光栅且音频
The last issue we introduced the basic principles of system control circuit and troubleshooting summary, the current analysis of the system control circuit of several maintenance examples. Example 1 Model: Hitachi VT-M747E (DH) Symptom: The display does not display when the power is on. Pressing the power (operation) button does not illuminate, and the rest of the buttons are also disabled. Analysis and troubleshooting: This failure usually occurs in the power circuit or system control section (see Figure l). Hitachi M747 machine, due to the use of Kaifu power supply, the operating voltage within the machine by the switching power supply and conversion, which can be observed before the inspection screen filament is lit, if bright, generally indicate that the switching power supply is working properly, Otherwise, the fault is in the power section. If the monitor (TV) screen is displayed as a white net with audio