The iPhone 7 screen dead? What does it mean? The iPhone 7 display screen keeps black after turn it on. In the beginning, I suspected that the iPhone failed to boot, so i take another cell phone to call my iPhone, the iPhone 7 is responding. So what causes the problem? We need to fix it.
First, dismantling the iPhone 7 carefully by phone opening tools, and then connect it with DC power supply to test its boot current, the current is normal, which confirms that the iPhone is turned on, but the screen no display issue.
Now replace the new iPhone display assembly, and then use DC power supply to measure the iPhone again, the boot current is normal, but the iPhone display screen still black.
According our experience, the iPhone motherboard backlight circuit damage can also cause this problem. Now, remove the iPhone motherboard, measure the grounding resistance value of J4502 with multimeter, the value is normal, which means the backlight circuit has no problem.
Open the WUXINJI Dongle to check iPhone schematic diagram, we can know that the backlight signal is connected directly with iPhone backlight IC U3701, now we determine that the iPhone iPhone backlight IC U3701 is damaged.
Apply some BGA paste flux on iPhone backlight IC, remove it with hot air gun and tweezers, and then clean the tin. Then, replace it with new iPhone backlight IC.
After finish the above step, install the iPhone and press the iPhone power button, now the iPhone 7 can be lit smoothly, the iPhone 7 display screen it back to normal.