How to Fix iPhone X without Face ID When the iPhone X Was Dropped

Date: Jun 30th,2020

Faulty model: iPhone X


Failure phenomenon


The customer describes that the mobile phone consumes power quickly, and it is powered down when not in use, and Face ID is not used.





Maintenance ideas


Fast power consumption is generally caused by the standby current of the mobile phone, usually caused by a short circuit of the circuit, the circuit is shorted due to falling or water intrusion, the best method is the elimination method and the burn-in method (Conditional customers can also use a thermal imager to detect).


Preliminary analysis


Disassemble the screen, connect to a regulated power supply, press the power button to trigger the current to jump from 230mA, since the trigger current is from 230mA, it should be caused by a short circuit in a load circuit.




Detection process


Using the elimination method, first start the single board, first exclude the external configuration, remove the motherboard connected to the regulated power supply, and perform the single board startup test. The current jump of the startup test is normal. The start-up current of the board jumps normally, so the fault point is locked on the external configuration (As shown in the figure).


1. Put the motherboard back into the case to test, press the power button, the current jump is normal.


2. Install the screen on the motherboard, press the power button to continue the current jump at 226mA, the original fault of the mobile phone appears.


3. Change the screen, press the power button, the current jump is normal.


4. Install the handset cable, press the power button, the current continues to jump at 226mA, and the original fault of the mobile phone appears.


5. Remove the earpiece cable and observe under a magnifying microscope to see if there are signs of water ingress or cracks.




6. It was found by the microscope that the glue wrapped by the three components on the earphone cable was obviously damaged. Remove the glue and measure the resistance to ground. One of the capacitors had a resistance to ground of 40.




7. The normal resistance of the capacitor to the ground should be about 300. Remove the damaged capacitor at the measurement solder joint and the resistance is normal.


8. The result of the separate measurement of the removed capacitor is that the capacitor has broken down. It is judged that the breakdown of the capacitor causes the circuit to short circuit and consumes power quickly. There is no face ID failure.



Maintenance process


Test the installation of a capacitor with the same size by welding.




Maintenance results


The power consumption problem is solved, and the face problem is also fixed.



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