If you have been charging your iPhone with cheap Chinese adapters, sooner or later this can lead to problems. We wrote about this in a separate article “How to charge your iPhone properly”.
Now if your iPhone has stopped charging normally, drains quickly even without use for a few hours, refuses to charge with various chargers, or even won’t turn on at all, the cause is likely to be inside the device in question.
In this article, we’ll describe what it means in practice to replace the power and charge controller in the iPhone, how it works and whether you can do something yourself at home.
This article does not contain detailed step-by-step instructions on how to replace this or that chip, although everything is shown in detail in the video below. However, after reading it, you’ll have a clear idea of how to repair an iPhone in case of charging problems.
U2 and U7 power controllers
Now, closer to the topic. In fact, there are multiple reasons why the iPhone does not charge (here it is described in more detail), but we will focus on what is hidden from human eyes and is inside the iPhone, namely the U7 power controller (power ic) and the U2 Tristar charge controller (charging ic).
The image below is a schematic of the iPhone 5S motherboard showing the locations of these microchips.
The Tristar U2 chip is part of the circuitry that is responsible for USB functions (including charging). The U2 chipitself is very “fragile” and can easily fail (burn up) due to power failures.
The name of the U2 chip comes from the iPhone 5 concept, as it was in this model that Apple first used it. In fact, U2 is just the name of an element on the board, where the letter U stands for microchip (e.g. the letter D is a diode, R is a resistor, C is a capacitor), and by pure coincidence this chip received the serial number 2.
On the motherboard there are also other microchips U3, U7, U5 etc. Starting with the iPhone 6, there is also a new chip on the board called “Tigris“, which works together with the aforementioned U2 Tristar and can also fail, either completely or only partially. The problem of improper charging and other related problems can therefore be directly linked to a defective Tigris chip.
Chip U7 is the power distribution controller and is responsible for generating voltage to the secondary circuits. The normal voltage of the iPhone primary circuit is 3.7 V. But not all iPhone components (screen, processor, camera, etc.) operate from this voltage, and some require a voltage reduction to 1.8 V, 2.5 V or 1.35 V.
The iPhone’s power distribution controller, named U7 on the motherboard, is designed to directly reduce voltage. Secondary circuits start working only after this chip is switched on, so they are completely dependent on it.
On other iPhone models, the charge and power controllers may be referred to by different names in the motherboard diagrams. For example, in the iPhone 6, the Tristar chip is already referred to as the U1700, and in different iPad models, for example, it is referred to by various other names. Despite this, most people tend to call the U2 charge controller and the U7 power controller, the same name, U2, even though the only correct designation is Tristar, regardless of the code designation on the boards.
Why the power/charging controller on the iPhone is failing and how to recognize that the battery is not the cause
There are many reasons why the iPhone doesn’t charge. Usually it’s one of three components: the Lightning charging connector, the battery, the U2 Tristar or U7 microchip. Let’s take a look at how we can discern which component it might be.
Charging connector: if the Lightning connector looks normal and there is no obvious physical damage or dirt deposits inside, this shouldn’t be the reason why the iPhone won’t charge. The charging port is essentially just a sort of relocated surface to bring power to a more convenient place within the phone’s design and user convenience, and there’s nothing prone to go wrong. From personal experience, iPhone charging issues are more likely to be rooted in a faulty cable or charging adapter. We recommend trying other charging components first, where you are 100% sure of its functionality.
Batteries: This is probably the first thing that comes to mind when your iPhone doesn’t charge. Yes, the battery can fail, and it happens much more often than with the charging connector. However, unless your iPhone is less than 2 years old, the likelihood of the battery suddenly failing without any previous symptoms is minimal. It’s also worth noting that the battery loses its capacity after extended periods of use, not in a single day. So, if your iPhone worked fine yesterday and stopped charging today, we can guarantee that the problem is NOT the battery.
Of course, you can try installing a different battery to make sure it’s not the problem, while we wouldn’t recommend removing your old battery at all, as you can just connect the new battery to the connector on the board to test it, without installing it into the device permanently.
Now that we’ve ruled out the cable and adapter, the Lightning charging connector, and the battery as possible causes, it’s time to consider a motherboard glitch as a possible cause. The most common case is a charging failure due to a faulty U2 Tristar microchip.
This glitch is often associated with the use of cheap Chinese chargers, especially automotive ones. Don’t forget one fact, CAR CHARGING with such a charger is a big mistake, you’d better throw it away right away! Many people like to buy cheap chargers and then ask – “Why did my iPhone stop charging?”
Overvoltage, if not immediate, can destroy a Tristar or Tigris or U7 microchip over time after several connections. This must then be professionally replaced in a service centre.
Replacing the power and charging controller on an iPhone
So let’s list the main symptoms that may occur and most likely will require replacing the power controller in your iPhone:
- iPhone discharges unusually quickly (replacing the battery does not solve the problem)
- iPhone refuses charging adapter (it happens that it charges only from the cheap Chinese one, but not from the original one)
- Incorrect charging (the screen shows the charging indicator, but the phone continues to discharge)
- The iPhone has shut down and won’t turn on even when I try a hard restart
- iPhone loses almost all of its charge value in a matter of hours
- iPhone gets excessively hot while charging
- iPhone only charges when switched off or in Airplane mode
Before replacing one of the microchips in the iPhone, an experienced technician usually performs a diagnostic on the motherboard itself and some of the components of the device. They will usually measure the current power consumption, check the battery, etc. If there is no increased power consumption, there is a 90% chance that the U2 Tristar microchip is defective.
To give you an idea of what the Tristar U2 and U7 chip replacement process looks like, below you can see one of the many YouTube tutorials on the subject.
As you can see, there are other elements on the iPhone’s motherboard, other microcontrollers that also affect the charging process and the distribution of power from the battery to other parts of the motherboard. Only an experienced technician can find the correct cause and understand which component to replace.
What you can do yourself
Now that you’ve seen it all with your own eyes, it’s fair to ask the question: Would you dare to do the same?
It seems to us that not everyone will decide to try it, even though it looks quite simple in the video. The truth is, of course, that you can irreparably damage your phone!
But if someone is a brave and handy person who does everything left-handed, here is a short list of equipment needed to replace the Tristar chip:
- Hairdryer
- New Tristar chip for your iPhone / iPad
- Assembly tools
- Microscope
- Soldering stations
- A pair of skilful hands
The most important thing is to experiment on an old and unnecessary phone. If you are going to do something yourself, always be very careful when doing it. In addition to the Tristar chip, there are other microscopic elements on the motherboard that can be easily damaged while soldering the chip.
And remember, a thorough diagnosis is necessary before replacing any component, as the U2 isn’t the only chip on the board that could be causing your iPhone to charge incorrectly.
From our point of view, the best solution is to contact a trusted service centre with a good reputation. Remember that not every service center will replace the chips on your iPhone motherboard, and some service centers may return the device after diagnosis with the verdict: unrepairable.
Often, equipment from a previous service will come in for repair. When we open the device, it often turns out that some components are missing from the phone (e.g. antenna module, display connector covers, etc.) So be very careful when choosing a repair shop to fix your iPhone!
How much does it cost to replace a Tristar microchip in an iPhone
Charge controller replacement costs:
iPhone 5S – 1200,-
iPhone 6 – 1500,-
iPhone 7 – 2100,-
iPhone 8 – 2300,-
iPhone X – 3500,-
Full price list can be found here
If you have any additional questions, please do not hesitate to contact me. contacts can be found here
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