Our customer sent an iPhone 7 Plus to us,
the problem is that the iPhone 7 Plus won't turn on. He wants us to fix it.
Trouble
phenomenon
The original problem with this iPhone 7
Plus is that the iPhone touch screen shows half bright half black after the
boot, when repaired this problem, the iPhone 7 Plus won't turn on.
Repair
process
After we received the iPhone 7 Plus, first
of all, we need to use JM-P01 Essential Toolkit to disassemble the iPhone, remove the
iPhone motherboard and then put observe it under the VGA Camera 7-45X Trinocular Stereo Microscope, there has traces of water, and many small
original components have been torn down.
Connect iPhone motherboard to the computer
with C48 MFI USB Cable, there is no response. With the help of YH898D hot air gun and tweezers, we remove the iPhone NAND
Flash, and then connect it to computer again, still no response.
Use Fluke 15B+ Digital
Multimeter to measure the booting power supply and
I2C bus, the data is normal. Now we start checking the disconnected iPhone NAND
flash that without connecting to the computer. Remove USB tube U4001, measure
the resistance of the substrate, we found the E4#(PMU-AOP-TRISTAR-ACTIVE-READY)
is short circuit.
Open the WUXINJIDongle to check the iPhone schematic diagram; We
can know that this point is connected to the CPU display IC U3703 C2#. So we
remove the U3703, and then measure the C2# and U4001 E4# again, the short
circuit fault has been resolved.
Reinstalling the iPhoneNAND Flash and U4001, and replace a good U3703, after
finish these, assemble the iPhone to test, the iPhone 7 Plus turned on
smoothly, the fault was solved.



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