Solve iPhone 7 no service after memory expanding

Fault Description: iPhone 7 happens no service after been expanded to 128.

The first step we do is to brush it into the latest iOS system, we found it can enter the system but no service.

So we need to disassemble the iPhone 7 to check the iPhone motherboard, with the digital multimeter to test the current and voltage,  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.

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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.

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The solution is put iPhone motherboard under the Trinocular Integrated 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.

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Finally, install the iPhone 7 and test it, now the iPhone signal is normal, the iPhone is working properly.