| 故障表现为：三无 检修与分析：开机检查5V电压只有2.5V,12V只有7.8V,拔掉负载，电压依旧很低，说明是电源板不良，代换U4（TL431）和U2(HPC922),故障依旧。又试更换U3(5571),还是一样。无意中用烙铁加热到Q4时电压恢复，更换Q4，试机修复。 |
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