Your iPhone won’t turn on because either the software crashed and needs to be reset or restored, or a hardware problem is preventing your iPhone from turning on. In this article, we show you how to troubleshoot and fix iPhone 8 Plus won’t turn on/current leakage with logic board repair. We hope you enjoy our sharing.
Step 1 Function Test
The iPhone won’t turn on, we will dissemble the iPhone to troubleshoot and repair. Use the DC power supply to power and test the motherboard. The motherboard shows current immediately when supplied power, this is normally caused by short circuit/small diode resistance of the BATT_VCC (battery voltage line) or VDD_MAIN (main power supply line)
Step 2 Diagnosis
We have measured the diode resistance of both BATT_VCC and VDD_MAIN, discorved the diode resistance of conpacitor from VDD_MAIN line is close to short circuit. As all the IC chips and capacitors connecting to the VDD_MAIN are possible to create the short circuit. In order to find the defect component, we use the temperature sensing method and rosin method.
Step 3 Troubleshooting
Connect the motherboard to the power supply, feel and confirm the area that gets hot by hand, we found there is large heating area in the backlight chip. To be accurate, use the rosin method to troubleshoot. The rosin on the backlight IC chip U5600 melts immediately when turn on the power supply.
Step 4 Repairing
Take off and replace the backlight IC U5600, remeasure the VDD_MAIN, the diode resistance showed normal.
Step 5 Reassemble & Test
Connect the motherboard to the screen assembly and power supply, use the tweezers to trigger booting, the iPhone boots normally, repair completed.
Please refer to below detailed video:
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Tools and Materials Used in This Video:
DC Power Supply
Hot air gun
Desoldering briad/solder wick