故障现象:刚开机时图象、声音均正常,一二分钟后图象色彩变淡、扭曲,并且伴音出现严重的沙沙沙的干扰声。此时换台,图象、声音又正常,但过一二分钟后仍旧出现上述现象。自动、手动预置选台均不能锁定。故障分析:伴音和图象均不正常,则可推断故障出在公共通道,又因电源部分和行扫描电路工作正常,因此故障可能是中频调谐回路失谐。检修:打开该机后盖,发现该机公共通道与伴音解调部分同在一个屏蔽的金属盒内,该屏蔽金属盒 Symptoms: just boot up images, sounds are normal, one or two minutes after the image fades, distorted, and the sound of a rustle of sand rusting noise. At this time for Taiwan, the image, the sound is normal, but after a minute or two still appear above phenomenon. Auto, manual presetting can not be locked. Failure Analysis: sound and images are not normal, you can infer the fault in the public channel, but also because of the power supply section and the line scan circuit is working properly, so the fault may be the IF tuning loop detuning. Maintenance: Open the machine back cover and found that the public channel and sound demodulation part of the same in a shielded metal box, the shield metal box