Troubleshoot: iPhone 7 Plus doesn’t boot and leakage 50mA

We received iPhone 7 Plus to repair, its problem is that the iPhone 7 Plus doesn't boot. It's been repaired once since the screen was half black and half bright. Now, we are going to troubleshoot doesn't boot issue.

Disassemble the iPhone 7 Plus by JM-P01 Essential Toolkit, 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 WUXINJI Dongle 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 iPhone NAND 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.

Tips:

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When you encounter problems, don't rush to repair, you need to observe it carefully before you start to repair.

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