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故障现象:成都HC340—2S2型电视机,此机是以μPC1031作场扫描输出电路。出现的故障比较奇特,每转换一个频道,图像或光栅要上下抖动几十秒,然后才能稳定。有时还出现帧幅缩小,如果调帧幅度电位器,使光栅上下满屏,图像或光栅就会周期性的上下抖动不止;有时还在屏幕下部呈现白卷边。分析检修:拆机检查,用万用表测量μPC1031的振荡、锯齿波形成、帧输出等
Symptom: Chengdu HC340-2S2 type TV, this machine is μPC1031 for field scan output circuit. The emergence of the fault is more peculiar, each conversion of a channel, the image or grating to jitter up and down tens of seconds, and then to be stable. Sometimes frame reduction occurs, if you adjust the frame amplitude potentiometer, the full screen up and down the raster, the image or raster will periodically shake up and down more than the occasion; sometimes appear in the lower part of the screen white curling. Analysis and maintenance: disassemble inspection, with a multimeter to measure the oscillation of the μPC1031, sawtooth waveform formation, frame output, etc.