Recently, theres a strange thing happening on the iphone 7, it can be boot but withou display, the iPhone LCD screen just always black. Whats going on? By the way, the iPhone 7 had been dropped before.
1. Disassemble the iPhone 7 by JM-P01 Electronics Toolkit, then measure it with DC power supply, at the beginning, the current is about 350mA, and then the current drops and the iPhone reboots. Usually, this problem was caused by iPhone Nand flash systme is damaged or it wasnt tested when loading with other peripherals. Now, our initial judgment is that the Nand flash is empty welded or IOS problems.
2. Connect computer to flash, when its ready to enter the normal mode, error 4013 is reported, then the phone into recovery mode. It doesnt seem like a system problem, so we remove the iPhone NAND Flash. 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 1, the NAND is welded back.
3. 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 2, the baseband chip is removed
4. After removing the iPhone 7 baseband, no solderdrop points were found. As shown in picture 3, using QUICK 861DW reworking station to weld the baseband back.
5. Reboot it again, the current i s normal and the iPhone screen can be display now. The iPhone 7 has returned to normal work.
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