iPhone 12 Pro common issue repair cases sharing based on repair experience.
C2164 short damage
This is one of the most common reasons for the large current leakage issue. Let’s find the location on the motherboard and Refox bitmap.
* The C2164 is relative to the PP_VDD_MAIN, if gets damaged will have a large current once connected with the DC power supply.
L4200 Pseudo Soldering
Press the power button or trigger to start up, if there is a small current change up and down. Then, there is a high chance it’s the L4200 pseudo soldering damage. The location of L4200 is just under the CPU.
We can resolder it or get it replaced with a new one.
iPhone 12 Drop Damage Issue Repair
The phone gets seriously drop damaged, and the motherboard gets deformed.
After disassembling the two layers of the motherboard, we can see a lot of pads are missing at the corner sides.
The single logic board can boot up normally, so we can fix the missing pads first on the PCB.
After that, the motherboard cannot boot again, so the pads missing is not the root cause for no start-up, we should keep checking.
Trigger to power on the motherboard and check the current on the power on button, there is only 0.21V voltage, normally it should be around 1.8V, as our repair experience, it with a high chance is caused by crystal Y3602 (32.768KHZ) damage.
Remove the Y3602 and replace it with a new one then test, the phone still can not be booted.
Track the underlay of the crystal Y3602, the clock wire and the PP1V8_ALWAYS power rail trace as below
It would be the inner wire broken, the solution for this kind of issue is jump wire.
First, scratch out the first layer of the motherboard slightly, till we see the joint point of the CLK and power.
Then jump wire to get the crystal chip connected with the joint dots.
● PP1V8_ALWAYS
● CLK_PMU_XTAL2_XOUT_32K_R
Please pay attention to the jump wire direction, do not reverse!
After jumping the wire, apply a little bit of UV mask and cured it with a UV lamp for insulation and fixation.
Then assemble the phone and test, the voltage on PP1V8_ALWAYS is back to normal and all functions are good. No boot issue finally gets fixed by crystal chip jump wire connection.
