Lenovo Y470 does not display share

A Lenovo Y470 laptop, it can start, but doesn’t display. The version : LA-6881P. Connect power supply, the standby current 0.018A, press the power button to start up, the current is 0.088A, it does not display.

 

Open the notebook, start up, test +5VALW +3VALW, all are ok. Then test PL501　+1.5VP, OK. But test +5VS, +3VS, they are 0V voltage, So check the 4-pin of U46, the voltage is 0V, too. Then check the G pole of Q99, the SUSP is 0V, It is normal. So check the D pole, the +VSB is 0V, it is not normal.... read more