Problem
The iPhone 6 can boot normally, but the LCD screen has no display, just shows black screen.
The backlight is normal; it can charge and receive the calls.
Solution
According the problem description, at first
we thought the screws was broken, after we disassemble the
iPhone by screwdrivers, the screws are fine.
This iPhone has a corrosive problem which
caused by water, but there's nothing wrong with display socket.
Test the resistance value with multimeter, all is normal, then we check the power
output of Light Control IC U1501, as shown in picture 7-11-1.
After checking, 4-Way power supply is
normal, which means the chip is working. Working conditions are available, and
the backlight also boosts, now it should be able to
display it properly. However, after test it, it still no display. Now we need
to check the signal from display socket to CPU.As shown in picture 7-11-2,
7-11-3, 7-11-4.
From the socket then through the inductor
and directly to the CPU, CPU peripheral circuit testing is also normal. Now we
try to replace the inductor, if it is still not working after replace the
inductor, so that's the CPU problem. Check motherboard under the microscope, there is a layer of glue on the
inductance of the physical diagram. As shown in picture 7-11-5.
When we remove the glue, we found the
problem, as shown in picture 7-11-6.
There is a group display inductors that
just fell down with the glue, and the solder pad on the inductor also dropped,
is that the problem? So we solder it with the solderingstation on the
motherboard.
Finally, power on iPhone 6, it can display
normally. As shown in picture 7-11-7.
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