iPhone X Cannot be turned on

Störungsphänomen

Press the power button to power on, the iPhone X cannot be turned on.

Störungsbeseitigung

Disassemble the phone and remove the display assembly, then connected to the DC power supply cable, the current reading on the ammeter is 50MA, which is abnormal.

Then separate the top layer and the bottom layer of the motherboard, then connect the two layers of the motherboards with test fixture iSocket and connected with the DC power supply machine to check the current again, the reading is still 50MA. This means the current leakage is not caused by the connection between the two layers of the motherboards.

Continue to measure the voltage and diode value on the upper layer, we found the voltage on C2771 and C2770 was 0, but the diode value was normal. 

According to the circuit block diagram,  the voltage was output from pin W16, pin W17, pin W18 on U2700(PMU), and then input to CPU via L2770.  

Try to replace another inductor L2770, turned on the motherboard, and checked the voltage again, the voltage back to normal.

After replacing the inductor, resolder the upper layer and the lower layer together, assemble all the parts, and tested again, the phone can be turned on normally, problem resolved.

iPhone X Motherboard Reparatur Fall