We believe that many people have
experienced the failure of the iPhone rooting and show unknown error code, it's
so frustrating. Here the case, the iPhone 6 Plus has been dropped before, and it
has replaced the display screen, after a while,
it cannot update, and shows iTunes error 56. When you're facing this situation,
what do you do? Here are some good suggestions.
1. Determine the error code. After rooting
and testing, it does report error 56. In most of the cases, faulty camera
circuits and NFC circuits will cause such a problem.
2. Disassemble the iPhone, we can found
that the motherboard has been fixed. The
previous maintenance have fixed NFC major control chip U5301_RF. Other chips are not fixed by observing its
appearance. In real repair cases, MIPI bus could cause error 56 report.
3. Use
multimeter to measure the diode data to ground of the MIPI bus of
the front and rear camera, both data are
normal.
4. Check the NFC circuit. NFC has two
chips. One is major control chip (U5301_RF); the other is minor control chip
(U5302_RF). In general, I first exclude the major control chip problems and
then the minor control chip problems. The dropped iPhone CPU and NFC signal circuits are easy to be
disconnected and the NFC solder pad is easy to drop joints. So, we remove NFC
major control chip U5301_RF. The solder pad does not drop any joints. Then
measure the its diode data to ground to CPU data
cable by multimeter and measure the resistance
of U5301_RF. These data are normal. Now, we doubt that NFC major control chip
U5301_RF is damaged. Replace the old one, but the problem remains the same. The
diode data to ground of several data cables from NFC to CPU are normal, so CPU
pseudo soldering problem can be excluded.
5. Then remove the NFC minor control chip
U5302_RF, we find some problems, the location of U5302_RF is shown in circuit diagram picture 7-21. The solder pad of
NFC minor control chip U5302_RF drops 3 joints. One
of the pins is power supply pin and other
one is ground pin.
6. Finally jump
wires to connect these pins and assemble NFC minor control chip
U5302_RF. Rooting goes on smoothly, the error code no longer appears.
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