Why click on the iPhone 5 touch screen, the
screen did not respond? You suspect that the problem maybe is the touch screen
in the first time, but when you replace the new touch screen, the touch
function still not working. In this time , you should realized that the problem
is not the screen, the essential question maybe is motherboard failure.
Use multimeter to test the diode
data of motherboard touch screen socket, finding no abnormity. The
material object of touch screen socket is shown in picture of 1-1.
1-1
Then measure the each power supply circuit
of touch control chip U12 (white touch) and touch processing chip U14
(black touch). The voltage of PP1V8_GRAPE and PP5V1_GRAPE_VDDH is normal, as
shown in picture 1-2.
1-2
Another measure the power supply circuit of
PP5V7_SAGE_AVDDH and PN5V7_SAGE_AVDDN, which is also normal, as shown in
picture 1-3.
1-3
The material object of touch control chip
and touch processing chip is shown in picture of 1-4.
1-4
Each circuit of touch chip becomes normal,
so touch process chip is very likely to be damaged. Replace the touch process
directly, as shown in picture 1-5.
1-5
Finally, after replacing a new touch
process chip, assemble iPhone and test. Touch function recovers. The iPhone 5
can back to normal work
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