Yesterday, a customer sent us an iPhone 7, the problem of this iPhone is that the iPhone 7 has no service after expanding iPhone Nand flash momory storage. After brushing it with iTunes, the iPhone is still no service, and it won't activated.
Use screwdrivers to remove the screws next to the iPhone lightning port, and then put iPhone 7 on the CPB screen separator, after a while, we can open the iPhone 7 easily.
Take out the iPhone motherboard, use digital multimeter to measure the power supply capacitors
around the iPhone baseband power IC, we found the PP_1V0_SMPS5 is shorted.
Generally, this case is caused by a short circuit of the iPhone baseband.
Remove the iPhone baseband power, and then measure the PP_1VO_SMPS5 again, it's
still shorted.
This is a designed flaw of iPhone 7
Qualcomm version, the iPhone baseband S5 power grounding connect point seems to
be disconnected, but not, and it cause iPhone
baseband burned.
The solution is put iPhone motherboard
under the Stereo Zoom Microscope, re-connect the S5 grounding connect
point, and re-install the iPhone baseband power, borrow a PP1V8_SDRAM on the
C3211, pass through a 2.2K resistor to C5701_RF, and then forcibly pull up
PP_1V0_SMPS5.
Now, use digital multimeter to measure the iPhone 7, the data measured is normal. Assemble the iPhone 7, turn it on, step by step to activate it. After entering the IOS system, the iPhone 7 has service, now the iPhone 7 is back to normal work.
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