Fault
Phenomenon
It can boot properly, but no touch
function.
Repair
Process
The touch circuits of iPhone 6S and iPhone
6 are different, the touch IC of iPhone 6S integrated on display screen. However, their working
principle is the same and the repair method still the same. Use multimeter to measure the touch
interface, it shows 1.8V touch power supply which is normal state. As shown in
picture 4-9-1.
Measurement shows touch interface +5.7V
power supply, it is normal. As shown in picture 4-9-2.
Measurement shows touch interface -5.7V
power supply, it is normal. As shown in picture 4-9-3.
After measurement, we can find that all
work voltages are normal. Now, we start to measure the diode data of SPI line
on display touch interface, all around 360, as shown in picture 4-9-4.This is
the normal range.
When measure the interrupt signal from display screen of display touch interface to the application CPU, we find that the
diode data of interrupt signal is infinite, which indicates that there is
disconnected from display touch interface to application CPU. As shown in
picture 4-9-5.
This kind of disconnect fault in phone
maintenance is basically caused by the application of CPU virtual welding, so we remove the CPU and reinstall it. Then power
on iPhone 6S and test touch function, its back to normal, the iPhone 6S failure
has been repaired.
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