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故障一:开机后有伴音,光栅刚出现便随“吱”的一声响声光全无,有时不等光栅出现伴音就消失了,马上再开机不能起动,数分钟后开机重复上述现象。打开机器后盖,测行管集电极电压,无光栅时0V,电源滤波电容C_(906)两端约290V,怀疑是保护关机,在开机瞬间测行管集电极电压110V正常(有关电路见图1),看来不是过压保护。断开ZD_(751)开机,光栅不再消失,证明是过流保护,因为此时可控硅Q_(751)已失去过流保护功能。当接近机器,呼出的空气触及显像管二阳
Fault 1: There are sound after boot, the grating will appear with the “squeak” sound no sound, and sometimes there is no grating raster disappeared, and then boot can not start, a few minutes after the boot repeat the above phenomenon. Open the back cover of the machine and set the collector voltage of the test tube, 0V without grating, 290V at both ends of the filter capacitor C_ (906) of the power supply. It is suspected to be shutdown protection. The collector voltage is 110V 1), it seems not over-voltage protection. Disconnecting ZD_ (751), the grating will not disappear, it proves to be over-current protection, because SCR Q_ (751) has lost over-current protection function. As you approach the machine, the exhaled air touches the second tube of the picture tube