Malfunction Phenomenon
The phone turns on normally, but the touchscreen unresponsive.
Try to replace a new display assembly and test again, the problem still remains.
Trouble Shooting
For the iPhone 8 Touchscreen Unresponsive Repair, we need to take out the motherboard and check the display touch connector J5700 and touch connector J5800, the measured value is normal.
So we connected with display assembly installed and connect the battery connector with DC power supplies, then shorted the pin 8 to the ground with tweezers, the system detects the power button pressed.
After that, we should check the voltage of the touch connector J5800.
Measure the voltage values of C5602, C5603, C5604 respectively, the measured value is normal.
But the value of C5601 is 0, which is abnormal.
The C5601 can’t get enough voltage caused by U5600 is damaged, the fault of touch relevant circuit or home button relevant circuit. So we can try to replace U5890 with a new one.
Then we assemble it and test again, the touch function can work normally. Problem resolved.
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