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故障现象:开机后,伴音正常,但无光栅,无字符。分析检修:测末级视放电路的视放管Q302、Q303、Q304c极电压均为200V,b极、c极均为0V,说明末级视放电路已截止。将加速极电位器顺时针方向旋动一定角度,屏幕中间出现一条水平亮线,说明场扫描电路有故障,致使保护电路动作,关闭三基色信号输出,以避免烧伤显像管。
Symptoms: boot, the sound is normal, but no grating, no characters. Analysis and maintenance: measured the final stage of the release circuit as the tube Q302, Q303, Q304c pole voltage is 200V, b pole, c pole are 0V, indicating that the last stage as the circuit has been closed. Rotate the acceleration potentiometer clockwise a certain angle. A horizontal bright line appears in the middle of the screen, indicating that the field scanning circuit is faulty, causing the protection circuit to operate and turning off the three primary color signals to avoid burns.