故障现象:接收图象很淡,对比度不足,无信号时雪花噪点很弱;同时屏幕显示的亮度不均,从左至右亮度逐渐变暗。且有肋骨条干扰,但伴音正常。分析与处理:从故障现象分析可能是高频和中频通道部分有问题,但检查结果这两部分是正常的。用示波器观察各级输出的信号波形,直到解码电路输出 Symptoms: the received image is very light, lack of contrast, no signal when the snow noise is weak; at the same time the brightness of the screen display unevenness, gradually dimmed from left to right brightness. Ribs and interference, but the sound is normal. Analysis and Processing: From the failure phenomenon analysis may be part of the high-frequency and IF channel problems, but the test results of these two parts is normal. Use oscilloscope to observe the signal waveform output at all levels until the decoding circuit outputs