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例1 故障现象:开机后无光栅、无图像、无伴音。分析检修:根据故障现象分析,可能电源电路有故障,测量主电源电压为+115V,正常。此时应测量NQ501的(33)脚电压,如果NQ501的(33)脚电压为0～3V,应测量电容C829的正、负极间电压。若C829的正、负极间电压为0 V,则应检查或更换VD830、R845、T803等元件。实际测量电容器C829的正、负极间电压为18～25V正常(参看电源相关电路图1),检查VQ842、VQ833、VD831、VD821、VD834、VD829、VQ836、R832、
Example 1 Symptom: No raster after boot, no image, no sound. Analysis and Maintenance: According to the analysis of the fault phenomenon, the power supply circuit may be faulty, measuring the main power supply voltage of +115 V, normal. In this case, measure the voltage of (33) pin of NQ501. If the voltage of pin 33 of NQ501 is 0 ~ 3V, measure the voltage between positive and negative of capacitor C829. If C829 positive and negative voltage is 0 V, you should check or replace VD830, R845, T803 and other components. The actual measurement capacitor C829 positive and negative voltage between 18 ~ 25V normal (see the power-related circuit Figure 1), check the VQ842, VQ833, VD831, VD821, VD834, VD829, VQ836, R832,