[phryne]

Model: Apple A1534
Board No. : 820-0045
Fault: the screen is black when turning on, we can hear the boot sound.

Inspection: the machine can operate. the backlight of the screen is not lit and the faint image can be seen under strong light.

first, measure the backlight boost circuit - no voltage
no voltage measured on two ends of D7701.

second, measure working conditions of U7701 - normal
Replace U7701 with a new one and test. Problem fixed.