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例5 长虹G2958型机故障现象:伴音正常,满屏“波浪”光栅上下翻滚。分析与检修:该故障跟电源滤波有很大关系,于是首先检查电源300 V滤波,经检查正常,接着检查场扫描电路供电电源滤波也正常,测量集成块TA8859和TA8427的各脚电压也正常,于是采用台灯仔细观察发现,场输出集成块TA8427的散热片与印制板的焊接处印制线断,进而造成电容C320不能接地,将断裂处用飞线接好,故障排除。小结:该故障是由于电源去耦电容C320接地端印制线断裂造成,用“电压法”测试各处电压均正常,用“台灯观察法”也不能方便地找到故障,因为当用台灯正面照射,反面观察时,不容易观察到,于是找另一个方式,台灯反面照射,正面观
Example 5 Changhong G2958-type machine Fault phenomenon: normal sound, full screen “wave” raster up and down. Analysis and Overhaul: The fault has a great relationship with the power filter, so first check the power 300 V filter, after checking the normal, then check the field scan circuit power supply filter is normal, the measurement block TA8859 and TA8427 the voltage is normal, So carefully observed using the lamp found that the field output manifold TA8427 printed circuit board printed with the printed circuit board disconnected, and then cause the capacitor C320 can not be grounded, the fault line with a fly pick, troubleshooting. Summary: The fault is caused by the power line decoupling capacitor C320 grounding line caused by the rupture, with the “voltage method” test the voltage everywhere is normal, with the “lamp observation method” can not easily find the fault, because when the front lamp irradiation , The reverse side of the observation, not easy to observe, so find another way, opposite the lamp irradiation, the positive view