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[例1]故障现象:一台韶峰牌SFC46—1型彩电,曾因出现“三无”检修过,检修后有时开机出现“三无”,有时开机正常,看一会儿后突然出现“三无”。分析与检修:开机检查,有电源启动声,随即可控硅发出“哒哒”的启动声,说明过流过压保护电路在工作。为了区分是过流还是过压,切断行输出管,并接上60W的灯泡,开机检查,保护电路仍在工作,确定是过压保护。取下可控硅,开机检测假负载两端电压为130V,说明开关电源输出电压过高。关
[Example 1] Symptom: A Shaofu SFC46-1-type TV, had due to the “three no” overhaul, after maintenance sometimes boot “three noes”, sometimes boot normally, after a while to see a sudden “three no ”. Analysis and maintenance: boot check, a power start sound, then the SCR issued a “da da” start-up sound, indicating over-voltage protection circuit at work. In order to distinguish between over-current or over-voltage, cut off the line output tube, and connected to the 60W bulb, boot check, the protection circuit is still working to determine over-voltage protection. Remove the SCR, the boot load voltage across the false load is 130V, indicating the switching power supply output voltage is too high. turn off