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故障现象 开机“三无”。该机故障前一直很好,但在收看中,突然发现机内冒烟,接着便不能收看了。 分析与检修 打开后盖,发现电源部分的滤波电容C926(22μF/160V)已裂开。测行输出管Q402(图上标为2SD1433,实际用BU2520)极间击穿短路,电源部分另一滤波电容C923(100μF/160V)顶部突出。根据这一情况,将C923、C926及Q402拆下后,接一只60W灯泡作假负载,开机发现电源输出电压接近200V(正常为145V)且不稳定,随着开机时间的延长,输出电压可慢慢下降,但最低也在160V以上。由此可初步断定故障是由于电源部分电压不稳、输出电压太高造成的。该机所用电源为自激式井联型开关稳压电源。其电源电路与东芝X56P型机心彩电的电源有些类似,但没有设置过压保护电
Failure phenomenon boot “three no.” The machine has been good before the fault, but watching, suddenly found inside the machine smoking, then you can not watch it. Analysis and troubleshooting Open the back cover and found that the power supply part of the filter capacitor C926 (22μF / 160V) has been split. Test line output tube Q402 (Figure marked as 2SD1433, the actual use of BU2520) Breakdown between the very short circuit, the power supply section of the other filter capacitor C923 (100μF / 160V) top prominent. According to this situation, the C923, C926 and Q402 removed, then a 60W bulb for a false load, power and found the power output voltage close to 200V (normal 145V) and unstable, with the boot time, the output voltage can be slow Slow down, but the minimum is above 160V. It can be initially concluded that the failure is due to the power part of the voltage instability, the output voltage is too high. The machine uses a self-excited power well-type switching power supply. Its power supply circuit and Toshiba X56P-type computer heart power somewhat similar, but not set over-voltage protection