The iPad 4 touch screen doesn't work with
you, because it's screen has a some weird issues. The iPad 4 lost touch
response in particular area of screen and could not be used normally and it has
changed two brand new touch screen to
test, but the problems are still the same. So, what's going on? According to
the experience, we can be sure that the problems happen in motherboard.
First, turn on iPad and install the
ketchpad software to test. We find that a part of vertical screen touch is
unresponsive to touch. Then teardown the iPad, measure the diode data of touch
screen interface by multimeter and we found that
one of the data cables’ diode data is infinite, as shown in picture 1-1.
1-1
Second, Opening the bitmap software, we can see that the data cable is connected
with the touch screen chip and testing point TP169 at the back, as shown in
picture 1-2 and 1-3.
1-2
1-3
The measured diode data of test point TP160
is more than 600, as shown in picture 1-4. The data is the same as that of
other cables’. Thus we conclude that there is line barrier between touch screen
socket and its back.
1-4
Finally, after confirming the problems,
solder a wire from touch screen socket to the test point at the back, as shown
in picture 1-5 and 1-6.After the jumper wire is down, restart iPad and
get into IOS test. Using ketchpad software to repeatedly test the place where
the original problems happen. And everything becomes normal. IPad now is
working normally. Using ketchpad software to test whether the iPad now is
working normally is shown in picture 1-7.
1-5
1-6
1-7
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