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[例1] 故障现象 一台环宇47C-2型彩电,开机几分钟后就频繁地自动关机,然后再自动开机。 分析检修 产生这种故障现象的原因有两个:一是负载有过荷现象,使保护电路动作,造成开关电源停振而自动关机;二是开关电源自身故障使电源无输出电压或低电压输出,造成行扫描电路停振而无光栅。首先要确定故障是由其中哪个原因引起的。短时间将保护可控硅Q903阳极断开,即人为将保护电路失效,再通电试机,故障依旧,说明故障并非负载所致,而是开关电源造成。该机开关电源由集成块IC901(STR4211)等元件组成。当故障出现时,IC901只有①脚输入
[Example 1] Symptom A Universal 47C-2 color TV, power off frequently automatically after a few minutes, and then automatically boot. Analysis and maintenance of this failure phenomenon for two reasons: First, the phenomenon of overload with the load, so that the protection circuit action, causing the switching power supply to stop automatically shut down the vibration; Second, the switching power supply itself failure to power no output voltage or low voltage output , Resulting in line scanning circuit stop vibration without grating. First of all, to determine which one of the causes of the fault is caused. A short time will protect the SCR Q903 anode disconnect, that artificial failure of the protection circuit, and then power test machine, the fault still shows that the fault is not caused by the load, but the switching power supply. The machine switching power supply from the IC901 (STR4211) and other components. When the fault occurs, IC901 only ① feet input