Diagnosing "No Power" on an iPhone 12 Pro: Real-Time Troubleshooting

In this video I show my typical procedure while dealing with an iPhone 12 Pro that has spontaneously stopped working and has developed a motherboard problem. It is good to have a plan of action for each type of problem you encounter.
My first step is always to check the DC power supply amperage draw before and after prompt to boot.
In this case, I see small amperage spikes after prompting the board to boot. If you were to see this problem (without viewing further into the video) do you know what you would do?
My next step was to check the power rails for shorts. Small amperage spikes are often caused by some short power rail. In this case, all the power rails I normally check seemed fine.
I could have also checked for voltage, but if a pmic output voltage is missing (but not short) I usually see a "brain dead" amp draw rather then a small spike (brain dead meaning small but steady amp draw). This is not a universal rule, but it is most often the case.
After measuring power rails I split the interposer to view the board components further.
This is when I found a loose Boost Coil. Loose Boost coils are a very common problem on the 12 series. It is likely this is the most common cause of spontaneous board problems on this series. Knowing signature flaws for each model is important, but only comes with experience.
This was an easy find because I knew where to look. You would be surprised how many CPU swaps are performed as a result of something as simple as a loose coil. If you don't know where to look, this problem can easily slip past you.

[@ezekielshub1188]

Thanks for another Tips Bro... learning a Lot from you. im a newbie for Board Level tech.

[@tbkmachinevencent]

Excellent job!

[@chrisami876]

Great tips on which lines you check first when you have no boot.

[@iBoardRepair]

Glad it was helpful!

[@haliimaaxmed]

thanks aaron

[@iBoardRepair]

You are welcome!

[@anirban9358]

nice video

[@JohnWilliams-zo5jf]

Great video, it’s been awhile

[@iBoardRepair]

I know! I will be releasing more again.

[@JohnWilliams-zo5jf]

@@iBoardRepair Thanks

[@sjang4010]

Hello from Korea, thank you Aaron for the great videos and tips. Your problem-solving ability is impressive. I have some questions.
I want to salvage my iPhone 12 mini which was water-damaged. First, it showed a green screen, so I thought the screen was the problem, but even when I replaced it with a new one, it still showed the green screen. Currently, the upper logic board is detached, and when I apply power supply and hold down the power button, it maintains 3.85 V with 0.13 A for a while, then spikes up for a short moment (like 0.2 A or 0.3 A) and it stays at 0.13 A again, and after 1 or 2 seconds it immediately drops to 0 A. After watching your videos, it sounds to me like the CPU tried to boot up and failed due to some short or something. I am planning to try your ways to figure out the problem, but do you have any guesses as to what might be the problem? (My rightmost 3rd and 5th test points from the bottom on the front of the upper logic board show shorted, but I couldn't find what they are even from your videos.)
I read that the data is encrypted with some chips. In the worst case, on the upper logic board, can I move the CPU and NAND to another working board, and will there be no problem using the phone and accessing my previous data?
I am sorry for asking specific things. I wanted to try fixing on my own so I have little knowledge. Even if the problem is difficult to tell, it is totally fine. Thank you!

[@user-wk8uv4ve7b]

Thanks

[@iBoardRepair]

No problem!

[@hosseinshemshad8597]

Nice job as always 👏. Hi bro. I asked you about that iPhone 15 pro which you changed the charging IC. Did you check 15 series works with another charging port to access the data?

[@iBoardRepair]

Hello, I have not done many tests with the 15 series yet. I've only used the original charging port at this point.

[@hosseinshemshad8597]

@@iBoardRepair I know there is a chip above the charging port which looks like LCD or battery chip which should swap for replacement. I repair cellphone for all functional. I'm curious what that chip do. I will tell you about it if I figure out. It's gonna be useful.

[@somewhere2023]

name your pcb spray pls

[@GsmAsib]

Which microscope do you use?

[@Carlcox89]

Very nice job!
I have a 11 pro with similar issue.
0.00A pre boot, then when I press power button it goes to 0.01A and returns back to 0.00A.
Im almost sure that it's a PMU problem, because there's no voltage being output by any of the buck/LDO of the PMU.
It has PP1V8_Always, so the trigger to turn on is there, but PMU is unable to output any voltage.
It has no short, neither main line neither secondary.
Y3000 oscillator is not outputting any frequency, so that leads me to conclude that PMU is at fault.
what's your thoughts?

[@iBoardRepair]

I would check the power rails mentioned in this video for a short first. Especially on the 11 pro, ram lines can be hard to find so you will want to double check those. In my ram swap video, I would have seen a similar symptom. Also of course make sure you have double checked all pmic outputs for shorts as well as nand power rails. Just from experience I can say it is very unlikely that pmic just doesn't work and delivers no power at all as the fault of the pmic. It is almost always something else. Also make sure your boost coil isn't loose, as that causes a similar symptom too.

[@Carlcox89]

@@iBoardRepair I checked every line and found no short. PP_GPU seems like it's short, but it is a low resistance line, so it's ok. sys boost coil is ok, tested and it provides 3.4V when pp_vdd_main is lower than 3.4V.
Since the crystal oscillator y3000 isn't giving any frequency, doesn't that point to the PMIC being at fault ? I suppose that PMIC only needs input voltage (PP_VDD_MAIN) for the crystal to be working at its frequency. right ? I mean, even if there was a short on some sec. line, the crystal freq. reading should be ~32khz. Or am I wrong ?

[@PhoneRescueExpert]

niceeee

[@iBoardRepair]

🙌

[@SergeREALGamer187]

I just did a cracked back glass repair on an iphone 12 Pro Max and the NFC coil was damaged and now the phone doesnt want to power on at all or show signs of life, can the damaged NFC coil be the cause?

[@iBoardRepair]

I think it will power on without that, but not 100 percent sure. I would just put it back to check.

[@conormeehan4402]

when I used my probes to tell the phone to boot it shows as 2 volts and 2.8 amps what does this mean ?

[@iBoardRepair]

It means you have a main short or a line that connects to main

[@usamaasifbutt5867]

Hi first view from Pakistan at 4.08 am 😂

[@iBoardRepair]

Thanks for watching!