故障现象:黑屏,无图像、无声音,也无子画面。检修:首先,怀疑视放电路有问题,试着播放AV节目,发现图像及声音均很正常,由此可以排除视放电路的故障。又怀疑行不同步,更换行晶振无效。于是怀疑高频头有问题,因该机为画中画彩电,有两个相同的高频头。考虑到两个高频头同时损坏的可能性很小,于是将其对调,主画面图、声立即恢复正常,子画面没有图像。仔细观察损坏的高频头,发现其引脚与常用的电压合成式高频头明显不同。查资料得知,该机采用的是 Symptoms: black screen, no images, no sound, no child images. Overhaul: First of all, suspect that there is a problem with the circuit, try to play the AV program and found the picture and sound are normal, which can rule out the circuit as the fault. Also suspected line out of sync, replace the line crystal oscillator is invalid. So suspected high-frequency head problems, because the machine is a picture-in-picture color TV, there are two identical high-frequency head. Taking into account the possibility of two high-frequency head damage at the same time is very small, so the tone, the main picture, the sound immediately returned to normal, no picture sub-picture. Careful observation of damaged tuner and found that the pin and the commonly used voltage synthetic tuner is significantly different. Check the information that the aircraft is used