The iPhone 6 3D touch is failed to work, no fingerprint identification, failed to open fingerprint function and so on. Why is that? How to fix?
Disassemble iPhone 6, observer it under the Trinocular Stereo Zoom Microscope, the water corrosion of the motherboard is obvious. However, different corrosion parts has different solutions. The details as follows
Fingerprint recognition failed
1. Inductor 1500 easily corroded damage caused by water damage, which will cause U1503 cannot work normally, it’s necessary to replace if the inductor gets damaged.
2. Since the small glass U1503 IC voltage value is 3.7V (VCC_MAIN) when iPhone is not booting and it has high voltage output value 16.5V when working, so if the IC gets water in, it would very easy to be damaged or short, which not only cause the fingerprint recognition failure but also cause leakage or high current when connecting with Rigol DP832 DP832A KORAD KA3005D DC power supply.
iPhone home button failure
After check iPhone 6 schematic diagram on WUXINJI Dongle, we know that the iPhone home button signal passes through the 3 tracks of the interface J2118 and then passes R2160 to iPhone 6 CPU.
Here we should notice that the resistance R2160 is easy to corrode and causes the HOME button unresponsive, it can be short connected by jumper wire to solve.
For the fingerprint part, there are several voltage to note:
One circuit is 16.5V sent from U1503 and through the FL2156 to J2118 interface, if the voltage is abnormal, it will cause the fingerprint function can be opened, but adding fingerprint HOME button has no reaction, The corrosion or damage of FL2156 will cause 16.5V not able to reach, resulting fingerprint has no reaction when adding fingerprint, short connection will solve the problem!
One circuit is U2100 output 1.8V voltage through FL2133 to the interface J2118, U2100 and FL2133 are easy to damage, it can be borrowed from another 1.8V voltage by connecting jumper wire to capacitor C2184. In addition, there is a 3.0V to be sent to the J2118 by FL2119, and FL2119 is easy to corrode and damage the fingerprint identification failure. The abnormal power supply of 1.8V and 3.0V will cause failure to open the fingerprint. These two voltages can be measured at the power on moment. U2100 is easy to damage which will cause the failure to open fingerprint function, short connection with jumper wire can be used.
If iPhone 6 fails to open fingerprint, first you need to use Fluke 15B+ Digital Multimeter to test whether the above mentioned voltage are normal, if several voltage are normal, then test if there is the situation of no voltage on iPhone 6 base, check if the corresponding resistance or inductance circuit get corroded or broken!
The iPhone motherboard structure is sophisticated, when you repair the iPhone motherboard, please be careful. There are many cases that not only did the iPhone fail to repair its original fault, but it added a new glitch to the iPhone because it accidentally damaged other parts while repairing the motherboard.