iPhone 7 Schematics, Boardview, Repair guides

iPhone 7 can’t be started for maintenance after falling

Machine model: iPhone 7
Malfunction: The mobile phone can’t be turned on.
Customer saidmobile phoneI fell. Later,no booting broke down. It was repaired locally but not repaired. Connect DC power supply switch RAM current to the store.
Fault analysis:
This kind of failure may be caused by the damage of CPU RAM, the abnormality of I2C0 I2C1 bus, the communication problem between the lower layer of CPU and RAM, and sometimes the damage of Nand will also affect it.
Maintenance process:
The disassembly probably locked the maintenance direction, 80% of which was related to the CPU. However, the customer said that it had been repaired before, so it’s best to look at the mainboard for any traces of maintenance, and find that the customer’s Baseband power supply is not installed. If no Baseband Version is used, it should not affect no booting. At most, the mobile phone Hang Logo(white apple)is restarted. Leave him alone for the time being.If we continue to observe the mainboard under the microscope, we can’t find any obvious damage. In this case, we can start to repair it with normal maintenance ideas.
lighting cable first step, I checked I2C0 and I2C1 buses and found that I2C0_AP_SCL was pulled down by only VCC of 0.3V or so, which is only connected with CPU, main power supply and u2301 independent boost chip. According to the principle of simplicity before difficulty, first disassemble the u2301 chip. After disassembly, directly measure the Connect the power supply, and find that VCC of I2C0_AP_SCL has been normal for 1.76V

iPhone 7 can’t be started for maintenance after falling Figure 1

This self-boosting chip can be directly used in short-circuit. The short-circuit method is shown in the figure:

iPhone 7 can’t be started for maintenance after falling Figure 2
After short-circuit was finished,Connect the power supply test directly found that Hang Logo(white apple)restarted. It never rains but it pours. Call the customer and explain the situation. The customer agreed to Update System.i4 soft Update System was used to find the card Update System. Under the microscope, it was found that the logic Update System was damaged.

iPhone 7 can’t be started for maintenance after falling Figure 3
Replace EEPROM, by the way, install Baseband power supply and directly activate Update System into the system test function. It is found that there is no earpiece in the mobile phone, and AUDIO CODEC IC is directly operated by experience. After replacement, it is found that the fault is still the same. Remove AUDIO CODEC IC Measuring diode value again and find that CLK signal of earpiece is too high to ground.

iPhone 7 can’t be started for maintenance after falling Figure 4

iPhone 7 can’t be started for maintenance after falling Figure 5
Direct replacement of u3301, installation test. There is no abnormality when the computer is tested and turned on, and all functions of the mobile phone are normal. At this point, the maintenance is over.