故障表现为:三无 维修与分析:本机通电试机指示灯不亮,开机检修怀疑是电源板有问题,检查3.3V无3.3V无24V,开始检修电源板,断开主板强行开启电源板,电源板电压有3.3V有24V。电源板各电压正常,然后接上主板检查主板,无3.3V,无24V,有万用表检查主板的3.3V短路发现U400(MT8227AAKU)短路了更换U400后开机试机一切正常。 |
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