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一、电路故障的排除故障现象:节目转发后,行场均不同步,画面混乱,伴音正常,各仪表状态均正常。分析检查:由故障现象可直接判断为视频信号无直流箝位。因为无直流箝位视频信号中的直流分量得不到恢复,同步电平将随图像电平的变化而改变,调制后的包络信号紊乱,以至接收机无法分离出同步信号,故出现上述现象。用解调器和VS1型波形监视器查调制器。中频载频输出正常,视频波形混乱,箝位监测孔无箝位脉冲。查箝位盒视频输出基本正常,箝位监测孔无箝位脉冲,进而证实了上述判断。
First, troubleshooting circuit failure phenomenon: program forwarding, the line are not synchronized, the picture chaos, sound normal, the instrument status are normal. Analysis and inspection: the phenomenon can be directly judged by the video signal without DC clamp. Because there is no DC clamp video signal DC component can not be restored, the synchronization level will change with the image level changes, the modulation of the envelope signal disorder, as well as the receiver can not be separated from the synchronization signal, so the phenomenon . Check the modulator with the demodulator and VS1 waveform monitor. IF carrier frequency output is normal, the video waveform confusion, clamping clamp hole without clamping pulse. Check the clamp box video output is normal, no clamping clamp clamp monitoring pulse, which confirmed the above judgment.