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故障现象:开机数10秒钟后,光栅逐渐变亮,且无噪波点,一会儿自动关机。检修:测116V,偏高5V左右。测可控硅SCR601控制极电压为0.8V,阳极应为12V,此时为零,说明可控硅动作,将加往IC801(28)脚的12V电压短路到地,因而整机停止工作。该机设有两级ABL保护和过压保护,为查明动作原因,将ABL第二级保护ZD603稳压管断开,保护电路不动作。此时开机后屏幕上一片白亮,调节亮度电位器,亮度无变化,测R、G、B三个视放管射极电压为6.8V,应为2.7V左右,集电极50V左右,应为125V左右,
Symptoms: boot a few seconds after 10 seconds, the grating gradually brighter, and noise-free point, while automatically shut down. Overhaul: measured 116V, high 5V or so. Measured thyristor SCR601 control voltage of 0.8V, the anode should be 12V, this time is zero, indicating the SCR action will be added to the IC801 (28) feet 12V voltage to ground, so the machine to stop working. The aircraft has two ABL protection and over-voltage protection, in order to find out the reasons for the action, the ABL second-level protection ZD603 regulator disconnected, the protection circuit does not move. At this time after boot a white bright on the screen, adjust the brightness potentiometer, no change in brightness, measured R, G, B three as the tube emitter voltage is 6.8V, should be about 2.7V, collector 50V or so should be 125V about,