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.
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.
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.
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
Then connect the motherboard with the DC power supply machine and check under the microscope, we can find the shorted component easily.
Refer to the bitmap, it’s the capacitor 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.
Then, let’s fix 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
We need to scratch out the root of the pad with a sculpture knife slightly first
After that, based on the “root” to jump wire and make a circle
Then solder a copper lug on the surface
Then cure and reinforce it with the UV mask and UV lamp.
Assemble and Test
Then assemble the two layers of the motherboard first with the 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.
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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