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故障现象:一台安华821BⅡ彩电工作一年,突然出现“三无”故障,电源指示不亮,无任何反应。分析与检修:根据上述故障现象说明是电源本身有故障。打开后盖,保险完好,通电测C_(995)有300V直流电压可判断整流部分完好。再测Q_(904)基极电压约+2V,表明该开关自激振荡电源未启振,怀疑启动电阻有问题,当在路测量R_(913)电压时,电源指示亮,电视正常工作。排除R_(218)值变大及启动电容C_(910)漏电后,断定Q_(204)性能不佳,导致“三无”。故障处理;用900kfΩ1W电阻将R_(913)并联,试加大启动电流,结果开机正常,启动自如。
Symptom: An Anhua 821B Ⅱ color TV a year, suddenly appeared in the “three no” failure, the power indicator does not shine, without any response. Analysis and Maintenance: According to the above symptoms shows that the power itself is faulty. Open the back cover, insurance intact, power test C_ (995) a 300V DC voltage can be judged rectification part intact. Then test base voltage of Q_ (904) about +2 V, indicating that the switch self-excited oscillation power supply is not starting, suspect start-up resistance problems, when measuring R_ (913) voltage, the power indicator light, TV normal work. Excluding the R_ (218) value becomes larger and starting capacitor C_ (910) leakage, it is concluded Q_ (204) poor performance, resulting in “three noes.” Troubleshooting; 900kfΩ1W resistor R_ (913) in parallel, try to increase the starting current, the result boot normal, start freely.