Thanks for the reply. I have a weired issue with two laptops both are YOGA 920. both turn on for a second then instantly off then a second after turn on again and off again. i flashed the bios. one of them is keeping on power led on but no screen. and it consums only 49 .milliAmp no more no less. the other one turned on after bios flash and posted but only for about 20s then freezed and the same ON Off issue again. i was looking for the boardview to trace the signals. it might be the vcore but not sure.