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例12:长虹51PT28A型彩电,出现“三无”,指示灯不亮,保险丝F801(4A/250V)烧断。用万用表电阻档测量电源集成块N821、开关变压器T804、光电耦合器NQ426、取样和比较放大器VQ827等元件均未见损坏。进一步检查整流、滤波电路,发现整流二极管V806、V807击穿,限流电阻R801烧断。V806、V807均采用BY254大功率整流二极管,R801采用2.2Ω/15W的电阻,更换上述各元件后,整机工作恢复正常,故障排除。相关电路见图6所示。
Example 12: Changhong 51PT28A color TV, there “three no”, the indicator does not shine, fuse F801 (4A / 250V) blown. With a multimeter resistance measurement power supply block N821, switch transformer T804, optocouplers NQ426, sampling and comparison amplifier VQ827 and other components were not damaged. Further check the rectifier, filter circuit, found that the rectifier diode V806, V807 breakdown, R801 current limiting resistor blown. V806, V807 are by BY254 high-power rectifier diodes, R801 with 2.2Ω / 15W resistor, replace the above components, the whole work back to normal, troubleshooting. Related circuit shown in Figure 6.