The iPhone 7 was dropped into ground accidantally, and then we press power button, it’s no responding. At first we thought it is not boot issue, but it can receive calls, so we judged it to be turned on without display.
Dissemble iPhone 7 and remove motherboard, then connect with DC power supply to test, the current is about 350mA when booting. In most of cases, these problems are from broken NAND system or it wasn’t tested when loading with other peripherals. Also the iPhone device was fallen off before, according to the symptom, we can judge that the NAND is false welding or system problems. After roughly judging the problem, it’s time to start the iPhone 7 maintenance.
Connect computer to flash, when it’s ready to enter the normal mode, error 4013 is reported, then the phone into recovery mode. It doesn’t seem like a system problem, so we remove the NAND. There is no problem to test the NAND to the CPU resistance, and the iPhone NAND is read normally on the test fixture. As shown in picture 7-14-1, the NAND is welded back.
According to the result of above test, we can get to know there is no problem with the NAND. It seems something wrong with the baseband. CPU self check will also be some errors reported. From the picture 7-14-2, the baseband chip is removed.
After removing the iPhone 7 baseband, no solder drop points were found. As shown in picture 7-14-3, welding the baseband back.
Reboot it again, the current is normal and the screen display is as shown in picture 7-14-4.
iPhone 7 maintenance is done here!
From the above iPhone repair process, we can conclude as that: the device doesn’t diplay and reports error are both caused by the empty welding of the base band after dropping.