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故障现象:开机后电源指示灯亮,但无光栅、无伴音。分析与检修:据用户讲,该机已在半年前修理过两次,都是前一天收看正常,第二天一开机便损坏“行管”。这次严重,有异味出现。打开机壳,对电路板进行检查,发现“行管”被换过,用万用表R×1kΩ档检测“行管”集电极对地电阻呈短路(拆“行管”测量已击穿)。对电源电路检查发现,保险丝R1001(4A)发黑已断,限流电阻R1003(3.3Ω/10W)开路,+B输出端滤波电容C914(470μF/160V)上部鼓起,测量开关管V901(C4111)击穿。同时还发现,电容C901旁有一只47μF/25V与C901并联。电阻R923、R925、R924被前修理者各焊开一脚而悬空。检查其他三极管、二极
Symptom: power indicator light after power on, but no grating, no sound. Analysis and Maintenance: According to the user, the aircraft has been repaired six months ago twice, all the day before watching normal, the next day a boot will be damaged, “governed.” This is a serious, smelly smell. Open the case, check the circuit board and found that the “line control” was replaced, with a multimeter R × 1kΩ file detection “line control” collector to ground resistance was short-circuit (demolition “line management” measurement has breakdown). Check the power circuit and found that fuse R1001 (4A) black has been cut off, the current limiting resistor R1003 (3.3Ω / 10W) open circuit, + B output filter capacitor C914 (470μF / 160V) upper bulge, measuring switch V901 )breakdown. Also found that the capacitor C901 next to a 47μF / 25V and C901 in parallel. Resistors R923, R925, R924 were left unconnected by the welders before welding. Check the other transistor, diode