iPhone 7 screen not showing repair

Fault model: iPhone 7
Fault phenomenon: The customer described that he could enter the system to hear the text message sound, but the screen did not display.

Maintenance process: Connect the DC power supply to the current and everything is normal, and even the Connect the power supply brain also responds as shown in the figure:

iPhone 7 screen does not show maintenance Figure 1.

The screen does not display as shown:

iPhone 7 screen does not show maintenance Figure 2.

Remove the motherboard to measure the basic conditions required for the display work, and measure to the display touch BTB connector(J4502) No. 7 pin PP_1V8 display screen VCC,diode value is OverLoad, the fault problem is found, the VCC is converted from PP1v8 through VCC FL3906 and renamed pp1v8_LCM_CONN, go Measure the diode value at one end of the VCC, and the other end has no value, and judge that the FL3906 is damaged.