23 June 2019

iPhone Motherboard Dead Repair | iPhone 7 Dead for no reason

How to repair iPhone motherboard dead

I still seeing countless of customers' iPhone been sabotaged by an inexperienced technician.
Many times they caused the customer more expensive to repair or either caused them to lost all the data memory.

I'm going to share a journey of how to repair a dead iPhone 7 that is fresh and nobody touch it yet.

This customer told us the phone suddenly off and unable to turn on anymore. Apple and other shop telling him is a motherboard problem.
Lucky he googled and decided to send it to much more experienced guy to do the works.  Thumb up!  :)

The well-prepared guy deserved good luck.

I love to repair this type of problem. Especially the phone becomes dead for no reason. Phone? Actually, I mean any model of smartphone.
But only meet the condition below.
  • No hard fall
  • No liquid damaged
  • No third-party charger used
  • No modification of hardware
  • Just suddenly become dead for no reason.

I made a video on YouTube if you are lazy to read the article, you can watch the video instead.

Continue to scroll down for long article that with details, why and how.

The article has much more to say. If I make the video too long, no people have time to watch entire video.


I love to repair this kind of case, ONLY when I'm the First-hand who fix it. 
Because - a lot of amateurs claim that they know how to repair the motherboard, but instead, they only know how to change the IC.
They don't know how to troubleshoot and would blindly change whatever IC that is related to power. Especially the "Power ic." 
Plus, some of them lousy soldering skill, they usually created a mess or more problem than it had. 

By the way... iPhone that suddenly becomes dead for no reason is usually because of a component failure. 

A component that is related to power.  
Might be an IC or small little thing like a capacitor. 
And most of the time, it is the capacitor.  

Because in term of lifespan:
 IC > capacitor

This is a capacitor that we see on a circuit board, inside TV or computer motherboard...
A capacitor has its own lifespan. It is just like a water tank, it will be broken if too old or overstress.

capacitor compare
Have you seen the bulging capacitors before? That's the problem. In the old days' people who repairing TV, they replaced a lot of these components that causing the TV malfunction.

Last time I fixed my Asus router by replacing faulty capacitors.
And my graphics card too.
You might wonder I can repair those too? Yes. for the sudden death issue, because most of the time I just need to fix the shorted components without a schematic.
But the iPhone uses a lot smaller size capacitor. As you can see, the red circle capacitors compare to my finger.
Some are tiny. Smaller than nose shit I can say.

So this kind of repair would be a simple job for me. But not for others...
In Malaysia, very few technicians are qualified to troubleshoot the iPhone motherboard problem.
Blindly changing parts or IC is those "fast repair shop" feature. Quick money.

Too bad that a lot of customers not knowing the difference between "fast repair shop" and "a specialist shop."

Louis Rossmann once said, "Mall shop" can't repair a thing. I bet the difference because I'm at the mall. LOL...   We should say never trust the "franchise repair shop," they just can't focus all the best technician in one place.
Best pros are always staying in one spot very long time.

Why not move into shop lot? I don't want the next morning open my shop and found out my roller shutter is half opened and inside is empty. You know what I mean in Malaysia.
The second benefit is the customers can wander around the mall while waiting. Easy parking and security...

Back to topic...

iPhone 7 motherboard shorted

 First step - Plug into Power Supply and read the responses.

When we haven't turn it on, it shouldn't be drawing any power.
And in this case, it's already drawing 0.8A when giving a good battery power which is 3.8v.
So this is the problem what we called "motherboard shorted"
For those who have some experience, they would think Oh yeah~ It's the VCC mainline shorted. Piece of cake.
But they found out the caps of vcc_main and batt_vcc have nothing short.
Example like this guy commented on my Youtube, screenshot below.

In my video, a pro can notice when the time I was giving the power slowly, the meter was showing the iPhone doesn't draw any power until reaching 1.8V. 

You can see the meter didn't rise until the 1.8V.

But once the power exceeds 2.0v above, the meter is showing immediately needle rising indicated something is drawing power.
To a much more experienced technician would already know something is tricky in this board.

That's why I said earlier, there are very few technicians that are qualified in the market.

Second Step - check for heated component 

If there is a water leak, the leaking spot will be cold.
But what if it's an electricity leak? Then the leaking spot will be hot.

In the traditional way of repair, we will force it to continue to receive the voltage then use our fingers to touch the board every component one by one. To feel which one is hot and it's a problem.

But with a well-equipped guy like me, would immediately waste no time and to take out the thermal camera to scan it.
Screw the finger or rosin technique.

Found out one of the IC is very hot. 97℃ 

A normal guy would think: "Found the problem, let's change it!"


Please... A correct way to repair is to analyze what's that IC for and find out the reason why it becomes a problem which is our

Third Step - read the diagram

I know lots of shop in Malaysia keeping your iPhone for two months or longer and then failed to repair it. You know why? Because they can't find the real problem and the whole iPhone is already messed up by blindly changing IC.

Okay, let's open up the schematic of iPhone 7, check the location of the IC and zoom in to read the label of this IC.
It's called U2301.

You might ask where is the schematic.
You can download it here.

Once we know the name of the IC, press CTRL + F to search and type u2301. You will find this IC's diagram.
Here I'm not going to teach whole diagram reading here. I try to make this article short.
Watch the video if you are intereste

From what we see in the diagram. This IC just to provide voltage to the other side.
According to what I read from this diagram, I understand this is one of the kick start systems that don't exist in the previous generation of iPhone. They called it Boost.

I'll try to explain noob version: Once the board detects the voltage is enough, this guy will make sure power stabled and pass it on to other few critical components.
Well, in every iPhone there is already have one similar IC. They added another one since iPhone 7.

So there is a high chance this guy is not the real problem.
Immediately we use a multimeter to check it's output circuit line.
How do we know where it goes out? By looking at the diagram, you will see "VOUT". Clearly, it means voltage out.
Then check those capacitors that on the bold line of VOUT.

The highlighted whole line is shorted. 

Fourth Step - How to check who is shorted in all those highlighted components?

Because there is only one component become faulty in this kind of sudden death issue.
The only way to find out is to give them exactly the voltage they need. By doing so, the real faulty component will take the heat itself.

First, we remove the IC that protecting them. Inside we make a jumper connect main voltage into this shorted line.

Remove this U2301 IC

Then solder two points with a wire. This is what we called - Jumper.
After that, connect to the power supply and start slowly supplying voltage on it. It's still showing shorted but this time would be different. Because the original source of the problem will take the heat itself.

If you don't have the camera, no problem. Use your finger.
or rosin technique.
As I said before, 99% is the capacitor problem for "Sudden death issue".
Remove it and the problem will go away.
Replace it if you want, but you might think isn't that will affect the device working properly?
It won't for this line.
Example let says the house you living have many reserve water tank, and if one of it is removed, your home would still have the water supply from outside.
Understand? Your house's continuous water supply is from outside. Not the tank.
But take note of this - Depends on the diagram and the capacitor purpose. I only explain more details in my course.

Once we removed the problem capacitor...

See? It'll still work without it and the IC but...

Final Step

We still need to solder the U2301 IC back on it though.
Because if the same problem happens on this line, it might burn a hole on the motherboard.
Countless irresponsible technician out there, they seem don't care. Maybe their volume of repair is low and I'm a specialist that only repair Apple, with that much of volume devices repaired... so I had encountered second-time capacitor problem that really burnt a hole. 

All memory data is not affected. Done.