Xiaomi smartphone owners often face situations where the standard charger ceases to function properly.The Redmi Note 8 Pro model came with an 18W adapter that, despite reliability, is prone to internal breakdowns. Disassembly of the power supply is required not only to replace burned elements, but also for deep diagnosis of the causes of failure.
Before disassembling, you need to be aware of the risks of high voltage, capacitors are located inside the housing, which can retain charge even after disconnection from the mains, and improper manipulation of energized components can lead to serious injury or damage to electronics.
In this article, we will take a closer look at the process of opening and analyzing the internal design of the adapter. You will learn about the necessary tools, disassembly stages and key components of the circuit. Safety when working with electrical appliances is the first priority, so you should not ignore the precautions.
Tools and workplace preparation required
Xiaomi’s power supply will require a minimum set of specialized tools to disassemble the power supply safely and efficiently. Using inappropriate items such as kitchen knives or sewing needles often results in damage to the plastic case or tool slipping with the risk of injury.
- 🔧 A set of precision screwdrivers (cross and flat) for unscrewing screws inside the body.
- 🛠 Thin metal spatula or mediator for neat opening of latch.
- 🔌 Multimeter to check for residual voltage on capacitors.
- 🧤 Dielectric gloves to protect your hands from possible electric shock.
The organization of the workspace is critical to the success of the operation: the surface of the table should be clean, dry and well-lit, and it is recommended to use an antistatic mat, as static electricity can damage the sensitive components of the board.
⚠️ Warning: Before starting any work, make sure the power supply is completely disconnected from the power grid for at least 30 minutes.
Don't neglect to check the tools for the integrity of the handle insulation. Even a minimal defect on the screwdriver handle can cause an electric shock when accidentally touching live parts under voltage. Dielectric protection is not just a recommendation, but a requirement.
☑️ Preparation for disassembly
Design features of the adapter Xiaomi 18W
The power supply for the Redmi Note 8 Pro is made in a compact, durable plastic case that is assembled without the use of visible screws, called a monolithic design designed to improve reliability and protect against dust, and is home to a compact pulse converter that provides stable current output.
The basis of the circuit is a control controller, which adjusts the voltage and current strength depending on the needs of the connected device. Quick Charge 3.0 technology, supported by this adapter, requires complex logic of operation of the control chip, which is the component that most often fails when voltage surges in the network.
| Component | Function | Typical malfunction |
|---|---|---|
| Transformer. | Galvanic decoupling and voltage change | Winding break or interturn closure |
| Condensers | Smoothing current pulsations | Bloating or loss of capacity |
| The rectifier bridge | Conversion of alternating current to constant current | Diode breakdown |
The heat sink system is worth special attention. Unlike high-powered computer units, there is no active cooling, so the heat dissipates through the housing and internal metal screens. Disturbance of contact between the components and the housing can lead to overheating.
Why doesn't the body have screws?
The process of opening the body without damage
The most difficult step is the initial opening, as the two halves of the body are connected by dense plastic latches around the perimeter. There is no official instructions from Xiaomi for disassembly, so you have to act by sampling and careful mechanical action.
Start by looking for the joint between the top and bottom of the case. Insert a thin mediator or the blade of a stationery knife (acting extremely carefully) into the gap. Slowly move the tool along the seam, listening to the characteristic clicks of breaking latches. Sharp movements can split the plastic.
- 🔍 Visually inspect the perimeter for hidden screws under the stickers (in this model they are usually not available).
- 🔪 Use a thin blade to cut the internal partitions if they interfere with separation.
- 💥 Do not use excessive force so as not to damage the internal wires connecting the board to the USB-port.
Once all the latches around the perimeter are pressed, the body should easily split into two, and inside you'll see a circuit board sitting tightly in a plastic bed, often additionally fixed with glue or silicone pads for vibration protection.
⚠️ Attention: Plastic in old power supplies becomes brittle, and when you try to open it can crack in places of stress, and act slowly and evenly around the perimeter.
If the case does not respond, you can slightly warm the seam with a dryer at low temperature, but do not overheat the device so as not to damage the internal components. Patience at this stage will save you time to find a new case.
Diagnostics and search for faulty elements
Once the board is successfully removed, you need to do a visual inspection of the components, look for signs of thermal effects, such as blackening, bloating of capacitors or cracks in chips, often the problem is a simple cliff of contacts or a fuse that has burned.
A multimeter is required to make a precise diagnosis. The first thing to check is the input circuit: the integrity of the fuse and the diode bridge. If the fuse is burned, it almost always indicates a short circuit in the power part of the circuit, and simply changing the fuse will lead to re-combustion.
Pay special attention to the high-voltage capacitor, which can hold dangerous potential even after prolonged discharge, and it is recommended to force it through a resistor or incandescent lamp before touching any elements of the board.
The output voltage is checked only after a careful connection to the mains, observing all safety measures. If the output is not 5 volts or the voltage is unstable, the problem may be in the feedback circuit or PWM controller.
Replacement of components and soldering
Repairing the Redmi Note 8 Pro's power supply often boils down to replacing burnt-out capacitors or diodes, requiring a soldering iron with a thin sting and a good quality solder, and it's important not to overheat the circuit board tracks, as they can peel off.
When replacing capacitors, strictly observe polarity; if the electrolytic capacitor is installed incorrectly, it will explode instantly when turned on; and pay attention to the nominal voltage of new elements, which must be equal to or higher than the original.
- 🔥 Use soldering paste or flux to improve the quality of soldering.
- 🧹 Clean the soldering place from flux residues with alcohol or a special cleaner.
- 🔍 Check the quality of soldering under increase for the absence of "cold" contacts.
If a controller chip burns, repairs are often economically inefficient, as the cost of the component and work can exceed the cost of a new adapter, but for experienced radio enthusiasts, this is a great practice.
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Use a braid to remove excess solder when soldering multipede components, which will simplify the installation of a new part and reduce the risk of damage to the board.
Assembly and final testing
After successful replacement of components and visual inspection of soldering quality, you can start assembly, make sure that all wires are packed into their channels and not be clamped with halves of the case, any tension of the wires is unacceptable.
The first turn on after repair is better done through a laboratory source of current with a restriction, so that in the case of a short circuit there is no re-cotton. If the device is stable and produces the correct voltage, the case can be assembled finally.
You can use a small amount of glue to fix the halves of the case or wind the tape if the latches were damaged during opening, the main thing is to ensure reliable insulation and no gaps.
⚠️ Warning: Do not leave the power supply on the network unattended in the first hours after repair, this will allow you to notice overheating or smoke in the event of a hidden defect.
A well-repaired product can extend the life of Xiaomi accessories for many years, but remember that the sealability of the factory assembly is almost impossible to restore.
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The quality of soldering and the correct selection of denominations of replaced elements are two main factors for the success of repairing the power supply.
Precautions during operation
Even after a successful repair or when using a new power supply, it is important to follow the rules of operation: do not allow moisture to enter the device and do not use it in high humidity conditions. Internal insulation may be disturbed, which will lead to a breakdown.
Avoid overheating the device by covering it with a blanket or leaving it under direct sunlight. High temperatures accelerate the degradation of electrolytic capacitors and can lead to repeated failure.
If you smell burning, sparkling or uncharacteristic buzzing, immediately disconnect the device from the network. Further operation of the faulty power supply can cause fire or damage to the smartphone.