How to fix iPhone 7 without service after memory expansion
We received an iPhone 7, iPhone 7 has no service and cannot make calls. The iPhone 7 has been displayed in other repair shops to 128GB.
After the iPhone Nand flash is expanded, the iPhone 7 always shows no service, search and eventually the white Apple restarts. After brushing the iPhone to IOS 12, it can enter the system, but still has no service and cannot be activated.
Disassemble the iPhone and use a digital multimeter to measure the power supply capacitance around the iPhone's baseband power IC. We found that PP_1V0_SMPS5 is shorted. Usually, this situation is caused by a short circuit on the iPhone baseband. IPhone baseband power is removed, and then measured again PP_1VO_SMPS5, it is still short-circuited.
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 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.
Install the iPhone 7 and test it, now the iPhone signal is normal, the iPhone is working properly.
After the iPhone Nand flash is expanded, the iPhone 7 always shows no service, search and eventually the white Apple restarts. After brushing the iPhone to IOS 12, it can enter the system, but still has no service and cannot be activated.
Disassemble the iPhone and use a digital multimeter to measure the power supply capacitance around the iPhone's baseband power IC. We found that PP_1V0_SMPS5 is shorted. Usually, this situation is caused by a short circuit on the iPhone baseband. IPhone baseband power is removed, and then measured again PP_1VO_SMPS5, it is still short-circuited.
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 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.
Install the iPhone 7 and test it, now the iPhone signal is normal, the iPhone is working properly.
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