故障现象:上部图像明显拉长、光栅稀疏,下部光栅密集、图像压缩并反卷重叠倒置。分析与检修:据故障现象分析,显然是场输出电路部分不正常。该机采用的是LA7840集成电路作场输出级,对I~2C总线控制的单片电视信号处理集成电路LA76810形成的场锯齿波电压进行功率放大,推动场偏转线圈,具体电路如图1所示。通常场扫描故障大多是由于场输出部分的电解电容变值、失效造成的(如:漏液、漏电等)。此机较新,使用时间不太长,查看各电解电容外形均完好,更换场输出N451(LA7840)集成电路外围的电解电容试机,故障依旧,分别检查低阻值的各个水泥电阻,也无问题。怀疑 Symptoms: the upper part of the image is obviously elongated, the grating is sparse, the lower part of the grating is dense, and the image is compressed and rewound. Analysis and Maintenance: According to the analysis of the fault phenomenon, it is clear that the field output circuit part is not normal. The machine uses the LA7840 integrated circuit as a field output stage, I ~ 2C bus-controlled monolithic television signal processing integrated circuit LA76810 formed field sawtooth voltage power amplifier to promote field deflection coil, the specific circuit shown in Figure 1 . Usually field scanning failure is mostly due to field output part of the electrolytic capacitors change, caused by failure (such as: leakage, leakage, etc.). This machine is newer, the use of time is not too long, look at the shape of the electrolytic capacitors are intact, replace the field output N451 (LA7840) IC electrolytic capacitor test machine, the problem remains the same, respectively, check the low resistance of the cement resistance, problem. doubt