iPhone 6s no display fault maintenance

Failure model: iPhone 6s

Malfunction: When the phone is turned on,no display can faintly see some patterns under the light.
Fault analysis:
This kind of failure is called no backlight failure. There is a row of small lamp beads on the 6S LCD screen. When the motherboard is working, there is a backlight booster chip, which provides VCC of 1622V to the LCD screen to light the lamp beads, so that we can see the displayed content. Most of the failures of this dark screen are the separated failures.
Then it is necessary to give priority to determine whether the screen is faulty or the motherboard is faulty. The method is to change the screen, and the fault remains the same, and the motherboard is faulty.
Maintenance process:
Remove the motherboard, and simple measurement shows that the backlight chip has no boost voltage, which may bediode; the one who lacks dialectical thinking, chip,Capacitor,Inductor, check them one by one, and check the backlight boost chip first.

iPhone 6S no display fault maintenance figure 1.
When Measuring diode value is removed, it is found that C2 pin Measuring diode value of the backlight chip is disconnected. C2 is the DWI bus of the backlight, which runs directly to the CPU, without any original in the middle, so that is where Measuring diode value in the middle is disconnected.

iPhone 6S no display fault maintenance figure 2.
The figure shows that the internal wiring of PCB layer is on the second floor. Let’s try to scratch PCB layer, give it a try.

iPhone 6S no display fault maintenance figure 3.
Measuring diode value is normal and fine after scraping PCB layer.

iPhone 6S no display fault maintenance figure 4.
Jump wire is connected and put back the backlight chip.

iPhone 6S no display fault maintenance figure 5.
Start-up test, the display is normal, here, the maintenance is over.