Free repair for our customer as he is our VIP customer. His iPhone 7 dropped into water which lead to the iPhone power button out of work. We doubt the motherboard occurred short circuit, Following the measures we take:
After disassemble the iPhone by JM-9102 Disassemble Tools, we can see the mist in the iPhone, so we need to handle the mist first. After it is done, measure the iPhone with DC power supply, apply some power on iPhone, and then press the Power-on button to check the boot current, it shows large current.
According to the current situation, this phenomenon should be the load of the power supply is short circuit. Now, we immediately use a method of feeling temperature to check, we found the lower part of the iPhone was hot. To narrow the scope, we can use the method of solder rosin to check, we found that one of the reserve capacitors in the light boost circuit was shorted.
With the help of YH898D hot air gun and Titanium Alloy Tweezers, we remove this capacitor, and then test it again, the current returns to normal.
Picture 10-3-1
However, the iPhone screen still no lights, sometimes we can see a little faint light. Using Fluke 15B+ Digital Multimeter to measure the voltage of lighting, it instantly shows 11V, then immediately turns 2.4V, sometimes turns 5V, and the voltage is very unstable. At this time, we know there's a problem with the lighting booster circuit.
Observing the iPhone motherboard under a VGA Camera 7-45X Trinocular Stereo Microscope, we found a glass-diode crack in the booster circuit. May be the user in the iPhone after the water, power on it and test, because of the continuously working, the diode is burned.
Picture 10-3-2
After replacing the new diode, the iPhone lights are back to normal, which means the iPhone touch screen can be display now!
Summary: The repairing of mobile phones is not only a theory, but also a variety of methods, such as Temperature-sensing method, Solder rosin method, and Microscope observation method, etc.
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