The iPhone 6S fell into water, and then it
stuck on white Apple logo after booting. It was repaired once before, when we
received it, the iPhone 6S in white Apple status and it will be restarted occasionally.
After remove the iPhone logic board, we found that the iPhone U2 IC and charge
tube has been replaced.
Check the iPhone logic board under a 3.5X-90X
Stereo Zoom Microscope 14MP HDMI Camera, there are small beads
around the chip, which is a serious mistake. Clean up the iPhone logic board
and then replace the new U2 IC and charge tube, but the problem still the same,
iPhone stuck on white Apple logo and restart occasionally.
Use Fluke 15B+ Digital
Multimeter to measure the diode data for iPhone
battery detective pin, the data is normal, the resistance of iPhone booting
condition is normal, and the voltage also is normal.
For the watered-iPhone, iPhone system is
less damaged. After consulting with the customer, we start to flash iPhone.
Connect iPhone to computer with iPhone lightning cable, the computer pop-up
prompts that USB is not recognized. We suspect that the problem will be in the
U2 circuit line. Take off the U2 to measure the resistance value.
After measurement, the U2 IC F4 pin
PP3.0V_TRISTAR is short circuit, this point is connected to power and an
inductor FL5408_RF next to an iPhone WIFI module IC, the U5411_RF receive amplifier is
connected to the head of iPhone logic board. In order to find the problem point
correctly, first we remove the FL5408_RF, measuring the ends of the inductor,
we found a short circuit at the end of the amplifier.
Remove the two capacitors on the bottom, the
problem still there. Remove the U5411 IC, and then measure it, the data is
normal. The glue around this chip is very soft，use QUICK 861DW hot air rework station in 150 degree to
remove it is enough, and please don't remove the capacitor next to it.
Finally, install the IC, re-weld the
FL5408_RF, test iPhone and it can be turned on properly.
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