Malfunction Phenomenon
The phone won’t be turned on.
When connecting the battery connector with the DC power supply, the current jumps to 250MA and then back to 0MA.
Troubleshooting
For the iPhone 8 Plus Won’t Turn On Repair issue.
According to the experience of repair, the fault might be related to the USB or charger-relevant circuit.
Take apart the phone and run the cosmetic inspection of the motherboard first. then remove USB IC U6300 and measured bonding pads, the measured value is normal.
From the circuit diagram, charging IC U3300 can get power from DOCK connector J6400 directly. Then we measure the voltage of C3301, which is normal.
The voltage value is abnormal, then we remove the U3300 and measured the diode value of the bonding pad, which is normal.
So we can get the conclusion that the fault is related to the U3300 because there is no voltage outputted from U3300. Finally, we replace the U3300 with a new one.
After replacing it with a new one, get the motherboard mounted and test again,charge function is back to normal. Problem resolved.
