iPhone 12 Pro Max Won’t Turn On Issue Repair Guide

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The iPhone 12 Pro Max, announced on October 13, 2020, is a high-end smartphone known for its advanced features. However, a serious drop can cause it to fail to turn on. This guide details the steps to troubleshoot and repair this issue.

Phone Details

Model: iPhone 12 Pro Max

Announced: 2020, October 13

Defect Phenomenon

An iPhone 12 Pro Max that has been seriously damaged by a drop may not turn on. In such cases, the following troubleshooting and repair process can be helpful.

Troubleshooting Process

First, let’s connect the motherboard with the DC power supply machine, there’s no current leakage. But when triggering the boot process by tweezer, the current jump to 1100mA directly.

01 Trigger to boot
02 1100mA directly

Next, let’s remove the foams around the connectors, and then hold the motherboard on the heating platform to separate the two layers of the motherboard.

03 Remove the foams around the connectors
04 Separate with the heating platform

After separation, not surprisingly, a lot of pads have fallen off, later we need to take a lot of time to fix the missing pads. But anyway, let’s fix the boot issue first.

When measuring the diode values on the power rails which are outputted from PMU to CPU, find one capacitor around the CPU is shorted to the ground.

05 When measuring with multimeter around the CPU
06 Find one rail is shorted to ground

Refer to the Refox bitmap, it’s PP1V2_IO.

As we can see, there are many components related to the PP1V2_IO.

To find out the exact shorted component, we need to use the rosin inspection method.

Apply rosin smoke on the surface of the relative areas on the motherboard

08 Apply rosin smoke on the Motherboard

Then connect the motherboard with the DC power supply machine and check under the microscope, we can find the shorted component easily.

10 the shorted capacitor around the NAND

Refer to the bitmap, it’s the capacitor C2941

11 C2941

Since it’s a filter-type capacitor, to avoid the potential heat damage to the NAND and connectors around it. We can just pick it off with tweezers directly.

After that, connect the logic board with the screen and boot with the DC power supply machine again, the phone can be booted.

12 Phone can be booted normally

Then, let’s fix the missing pads on the middle layer.

13 The missing pads on the middle layer

Fixing the missing pads is not very difficult but requires a lot of patience.

For the pad that has no connection point

14 For the pad that has no connection point

We need to scratch out the root of the pad with a sculpture knife slightly first

15 Scratch out the pads

After that, based on the “root” to jump wire and make a circle

16 Make a circle

Then solder a copper lug on the surface

17 Solder a copper lug on the jumped wire circle

Then cure and reinforce it with the UV mask and UV lamp.

18 Cure with the UV lamp

Assemble and Test

Then assemble the two layers of the motherboard first with the heating platform

19 Heating platform

When the motherboard cooling down, assemble the phone to test and all the functions are OK.

The issue gets resolved by removing the damaged capacitor and recombining the two layers of the motherboard.

iPhone 12 Pro Max Won't Turn On

Summary

The iPhone 12 Pro Max issue of not turning on due to serious drop damage was resolved by:

  • Removing the damaged capacitor (C2941).
  • Recombining the two layers of the motherboard.
  • Fixing the missing pads.

This repair requires careful inspection and precise work to ensure the phone is restored to full functionality without causing additional damage.

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REWA Academy

As an enthusiastic educator and expert in mobile technology, REWA Academy has dedicated its career to empowering individuals through technical education. With a keen focus on cellphone repairs, they have developed comprehensive online and offline courses at REWA Academy. Their expertise spans a wide array of areas, including iPhone repair training, phone hardware, software, and advanced troubleshooting techniques. Through their writings, they aim to demystify mobile technology complexities, making it accessible and understandable for both novices and professionals in the field.

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