Nowadays, i believed that most of people
like to play the phone before sleep, that's what i am. But, have you ever met
the phone 5s suddenly turns black and cannot be turn on? If you have met, i
think you will be insomnia. That is a bad thing. Now, we can find the reason
and get the solution to fix it.
First, use an adjustable power supply to
charge it and charger shows 4.28 A current flow (picture 1-1), which is an
obvious shout circuit. Use multimter to measure the diode data to ground of
battery interface, which is normal. We continue to measure and find that the
main power supply PP_VCC_MAIN is short circuit to ground.
1-1
Second, observing under microscope, we find no abnormality on the
surface of capacitors on the circuits connected with PP_VCC_MAIN. We use
burn-in method to check the faulty points, using an electric soldering iron to light rosin on the circuits.
We find a capacitor under CPU is extremely hot and it burn out the rosin. The
capacitor’s color changes from white to transparent, as shown in picture 1-2.
The discolored capacitor is shown in picture 1-3.
1-2
1-3
Third, After checking the circuit diagram, we know that the location
number of short circuit capacitor is C358, as shown in picture 1-4.
1-4
Fourth, Use hot airgun to remove C358 and use multimter to measure the diode data
to ground of the two ends of C358, which is 0, as shown in picture 1-5.
1-5
Finally, after removing the capacitor,
measure the diode data to ground of PP_VCC_MAIN, which is normal. Plug the
adjustable power supply and the standby is normal. Triggering it on, the
current change is normal. Assemble it on iPhone and test other functions, all
is fine, the iPhone 5s can back to normal work.
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