Malfunction Phenomenon
The phone can’t start up with leakage current.
Trouble Shooting
For the iPhone X No Start Up With Current Leakage issue.
First, disassemble the phone and run the cosmetic inspection of the motherboard. There is no bear deformation and water damaged.
Then connected with DC power supply to check whether the start-up current curve is normal or not. The reading on the ammeter is 600, which is abnormal. So we can touch the motherboard with one finger when connected with the DC power supply to feel if any component is hot. (Or we can use rosin inspection method or thermal camera to check)
After checking, we find the location of the Audio IC U4700 is burning hot.
Then we detach two layers of the motherboards from each other. Refer to the circuit diagram, the C4801 is connected with U4700, then we measured the C4801, and the diode value is 0 which means it’s shorted to ground.
So we can try to remove C4801 afterward, the issue still remains.
After that, replace the heat component U4700. Then test again the phone can be boot up normally.
Solder back the two layers of the motherboard, then the issue get resolved.
Tips
From this case, as we can see the issues of no start-up might be caused by many different reasons, maybe NAND, Audio CODEC IC, USB IC, etc. So when repairing this kind of no start-up issue, if you have no idea about how to repair then you can follow the below tips to do the troubleshooting
- Try to separate and test with fixture (like iSocket) to see if the function back to normal or not
- Try to check with thermal camera, rosin inspection method, or like in this to feel with finger to find the hot component
iPhone X Motherboard Repair Course
