iPhone X kann nicht booten, weil der Boost-Kondensator beschädigt ist

Received an iPhone X can not boot. Confirmed with the cell phone owner, the issue happened after the phone dropped on the floor. 

Prozess der Fehlersuche

Normally the cannot boot issue caused by drop damage might be caused by poor soldering between two layers of the motherboard. First, we can connect the motherboard with the DC power supply and check the boot current value, and there is a 700mA large current once connected with DC power.

Touch the motherboard to feel the heat, the earpiece speaker connector and camera connector is extremly hot. So we can make a preliminary conclusion the issue is not from the outside of motherboard but from the inside parts of motherboard. 

Then seperate the motherboard with heating platform. 

Motherboard Separation Heating Platfrom For iPhone

After separating, power the logic board with DC power supply first.

It’s found the small capacitor which under the boost IC with get hot (rosin on the surface get melted), check the Refox bitmap, the capacitor is C3111, a filter type capacitor.

So we can just take it off with tweezer directly

Connect with DC power to test again, the boot current became lower

While, the 0.627A boot current without trigger on is till too high and  abnormal, there should still have some shorted components.

Continue to heat with the DC power supply machine, and it’s found the rosin on the C3112 also get melted.

The C3112, as we can see from the schematic is also a filter type capacitor. So we can also just remove it directly.

Testing

After removing the capacitors C3111 and C3112. Connect with DC power supply again to test, current value back to normal. Connect with screen, trigger power on and test. The phone can boot normally and all the functions are also tested OK.

So we can solder back the two layers of motherboard, and assemble the phone.

After assembling, test again. All functions are OK.

Zusammenfassung

Finally, the can not boot issue get resolved by removing two filter type capacitors.

And the skills that you need to handle

1. How to separate and solder back the two layers of motherboard with heating platform
2. Rosin inspection method
3. Reliable handwork to remove the shorted components with tweezer precisely