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(2)测量关键点电压。在开机后,测量保护电路光电耦合器N505的②脚电压,如果该脚电压由正常时的高电平变为低电平,则是以N505为核心的保护电路启动;如果N505的②脚电压始终为高电平,则是开关电源初级以TDA4605为核心的保护电路启动。如果判断是以N505为核心的保护电路启动,可通过测量晶闸管V306的控制极和晶闸管V505的控制极电压,判断故障范围。
(2) measure the key point voltage. After turning on the power, measure the voltage of pin 2 of the photocoupler N505 of the protection circuit. If the pin voltage changes from high level to low level during normal operation, the protection circuit with N505 as the core starts; if the voltage of pin 2 of N505 Always high, then the primary power switch to TDA4605 as the core of the protection circuit starts. If it is judged that the protection circuit with N505 as the core is started, the fault range can be judged by measuring the gate voltage of the thyristor V306 and the gate voltage of the thyristor V505.