iPhone X Won’t Turn On – Large Boot Current Repair

First, run cosmetic inspection of the motherboard. The motherboard is not deformed or water damaged.

Then connect the motherboard with the DC power supply. We can see that there is no current leakage. Judging by this, the three main power supply rails, PP_BATT_VCC, PP_VDD_MAIN and PP_VDD_BOOST are in normal condition.

Continue to measure the current boot. The reading is larger than normal value. We can confirm now that the fault is probably related to the 17 power supply rails outputted from PMU.

Now we need to separate the motherboard to confirm whether the fault is related to the upper layer or the lower layer.

Place the motherboard on the specialized Heating Platform. With temperature of the platform reaching the set temperature, pick up the upper layer with tweezers carefully. Continue to take the lower layer off the platform.

Get the upper layer booted up with tweezers. The boot current is still larger than normal value. We can confirm now that the fault is related to the upper layer.

So our next step is to check the 17 rails outputted from PMU one by one.

Judging by the measured value, PP3V0_NAND has shorted.

Since there are many components on PP3V0_NAND, we can locate the faulty component with rosin detecting.

We find that C2649 has been damaged with rosin detecting.

Let’s try to detach C2649 from the board and see how it works. Remove black adhesive around C2649 first. Then we can just remove it with tweezers slightly.

Again, get the red probe grounded. Touch the two pins of C2649 with the black probe. The measured value is normal. We can confirm now that the shorted condition is caused by damage of C2649.

Next thing we need to do is to solder the two layers together. Place the lower layer onto the heating platform. Power on the heating platform and apply some Paste Flux to the third space PCB. Then get the upper layer in position.

Get the display assembly installed. Connect the battery connector with the DC Power Supply and get the motherboard booted up with tweezers. The boot current is normal. The phone comes with normal display and can get access to the system.