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三、电源与保护电路维修实例[例1]夏普29ADl F彩电,开机后,有高压建立的声音,随后自动关机,开关电源输出电压上升后又降到正常值的1/4左右,指示灯亮灭正常。分析与检修:根据故障现象,初步判断是保护电路启动。抓住开机后、自动关机前的瞬间,测量微处理器的30脚电压,为低电平1 V左右,判断是微处理器中断口30脚外部故障检测电路引起的保护。采取逐个拆除检测二极管D408、D520、D1712、D1608的方法,开机后仍发生自动关机现象;测量Q1605的基极电压,开机的瞬间有零点几伏的上升电压,判断灯丝电压过压保护电路启动。
Third, the power supply and protection circuit repair example [Example 1] Sharp 29ADl F color TV, boot, there is a high pressure to establish the sound, and then automatically shut down, the switching power supply output voltage rise and then down to about 1/4 of the normal, light off normal. Analysis and Maintenance: According to the fault phenomenon, the initial judgment is to start the protection circuit. Seize the boot, the automatic shutdown before the moment, measuring the microprocessor 30 feet voltage, low 1V or so, to determine the microprocessor interrupt port 30 feet external fault detection circuit protection. Take one by one to remove the detection diode D408, D520, D1712, D1608 method, the boot still occurs automatically after the shutdown phenomenon; measured Q1605 base voltage, boot moment there are a few volts rise of a few volts to determine the filament voltage overvoltage protection circuit starts.