main board: pm_a_hpc_s mv_mb_v1

Defect :
Inserting the power connector without pressing the power button turns on the power indicator and the fan runs for a few seconds, then stops. the power indicator always stays on. Keeping the power button pressed for a few seconds, the power indicator turns off and then on again, the display remains black.
  Even without the power button (physically removed from the motherboard), the defect remains. Absorption 800 milliamps constant.
We accept suggestions and scheme. Thank you and good job to everybody .
reprogrammed U12 = MX25L1605 the status remains unchanged .

Try to connect a post card.
Maybe it,s help to recognize a problem.