iPhone 6 Plus no booting maintenance

Machine model: iPhone 6 Plus
Malfunction: charging at night, the next day the mobile phone no booting, the customer sent a single board.

iPhone 6 Plus no booting maintenance figure 1.
Fault analysis: There are many reasons for this no booting fault, and some customers also describe it as no booting with a dark screen or no display, so it’s up to us to analyze this kind of problem in detail.
Maintenance process: For problems like this, I usually connect DC power supply switch to see current of change of current first. If current change is normal, it is likely to show the problem over there.

After receiving DC power supply, it was found that the current of mobile phone short-circuit switch was not current of change. For problems like no power on, first check whether the power-on key was 1.8V VCC or not, and it was found that VCC was only 1.3V VCC which was obviously low.

iPhone 6 Plus no booting maintenance figure 2.

After discovering that VCC is low, power off and measure the ground value of the power-on key. It is found that the ground value is normal, and there is no case of being pulled down or Short circuit.

iPhone 6 Plus no booting maintenance figure 3.

Look for the pull-up resistor of the phone’s power-on button, and test whether there is something wrong with the pull-up 1.8V VCC.

iPhone 6 Plus no booting maintenance figure 4.

One end of the 1.8V pull-up is normal, but the other end of VCC is only 1.3V. It seems that it has nothing to do with the end of PP1V8_ALWAYS. The problem must be on the BUTTON_TO_AP_HOLD_KEY_L side.

Microscopically observe whether the relevant originals have corrode or are damaged (no problems are found during observation), and now we can only dismantle them one by one, but according to my experience. diode; the one who lacks dialectical thinkingThe possibility is relatively high, because Capacitor is usually damaged directly by Short circuit, while Inductor will not pull down or Short circuit.

iPhone 6 Plus no booting maintenance figure 5.

First, remove the diode, and then Connect the power supply measures VCC of the power-on key. It is found that VCC is normal, and then the screen Connect the power supply switch is tested to enter the system normally. Because the customer didn’t provide the power-on password at first, there is no way to enter the system test function.