Xiaomi Power Unit Disassembly: Detailed Guide with Photos and Repair Tips

Introduction: why to disassemble the power supply and when it is justified

Xiaomi’s power units are some of the most popular on the market, thanks to their combination of compactness, power and affordable price, but even they are not immune to breakdowns: capacitors burn out, transistors fail or simply stop working. USB-Disassembly of the power supply may be necessary for diagnosis, repair or upgrade, but it is not an easy task. Inside you are waiting for high-voltage circuits, adhesive connections and fragile components that are easily damaged.

Before you start a screwdriver, you should honestly assess your skills. If you have never dealt with a soldering iron or do not understand the principles of operation of pulsed power supplies, it is better to consult a specialist. Disassembling the Xiaomi power supply without experience is fraught with not only failure of the device, but also the risk of electric shock - even after disconnecting from the network, capacitors can retain charge. In this article, we will discuss in detail the process of disassembly, tools, nuances for different models and give tips on how to avoid errors.

Special attention will be paid to power supplies from Xiaomi Mi Charge chargers (18W/20W/33W/65W/120W), Adapters for notebooks Xiaomi Notebook Power Adapter, as well as wireless charging stations Mi Wireless Charging Pad. Despite external differences, most of them understand the same technique, but there are important exceptions – for example, models with a cast case or double-sided adhesive connection.

Preparation: security tools and measures

Before disassembling, you can assemble everything you need, and without the right tools, you can damage the body or the components inside.

• 🔧 Plastic mediators or openers to carefully separate the glued parts of the body. Metal tools can leave scratches.
• 🔨 Set of screwdrivers (cross-haul) PH00, flat 1.5 mm, torks T5/T6). Xiaomi often uses screws with non-standard slits.
• 🔥 Hair dryer or heat gun - for softening the glue (temperature not higher than 80)°C, or the plastic will melt).
• 🧲 Magnetic mat or tray – so as not to lose small screws and details.
• 📸 Smartphone for photography – capture each step so as not to confuse the order of the assembly.
• 🛡️ Isolating gloves and glasses – protection against accidental breakdown of capacitors.

Important: Xiaomi power supplies often contain capacitors that retain charge for up to a few days after disconnecting from the network. Before disassembling, be sure to discharge them by closing the leads with a screwdriver with an insulated handle (hold on to the handle without touching metal!). If you are not sure about your actions, use a multimeter to check the voltage.

⚠️ Note: Some models (e.g. Xiaomi) 65W GaNs have a two-way circuit board with static-electricity sensitive chips. Only touch the board with a grounded soldering iron or an antistatic brush.

Step 1: Disassembly of the body - glue vs. screws

The housings of Xiaomi power supplies come in three types:

1. Glued (most models until 2020, for example, Mi Charge) 18W).
2. On screws (new models like Xiaomi) 120W HyperCharge).
3. cast (indissoluble, for example, some wireless charging).

If the body is glued, start by heating the seam with a hair dryer (keep it 5-10 cm away so that the plastic doesn't deform). Then gently insert the plastic mediator into the slot and guide it along the perimeter, gradually dissociating the halves. Don't apply excessive force - there may be latches inside that will break.

In models on screws, unscrew all the mounts first. Note that sometimes the screws are hidden under stickers or rubber legs. 65W Two screws are hidden under the label with specifications - it will have to be carefully put with a knife.

⚠️ Note: Xiaomi power supplies often use disposable screws (such as notches that break off when unscrewed).If you plan to reassemble the device, replace them with standard screws. M1.6 or M2.

Step 2: Printed circuit board extraction and diagnosis

Once the lid is removed, you will see a PCB secured with screws or covered with a compound (in cheap models). Xiaomi power supplies typically use the following key components:

• 🔌 Primary circuit (network filter, diode bridge, capacitors, transistors).
• 🔄 Transformer (heart unit, converts high voltage to low voltage).
• 🔋 Secondary circuit (rectifying diodes, output capacitors, controller) USB-PD).
• 🛡️ Protective elements (waristors, thermistors, fuses).

Before you touch the fee, check it for:

• 🔥 Blackened or bloated capacitors (especially electrolytic).
• 💥 Burned resistors or transistors (usually with black dots or cracks).
• 🔗 Circuit roads (often near the USB-jack-up).
• 🧹 Dust and dirt (may cause overheating).

For diagnosis, use the multimeter in diode or resistance mode. For example, call the primary winding of the transformer - the resistance should be within 10-100 Ohms. If it shows a break or short circuit, the transformer is defective. Also check the fuse (usually located next to the mains connector) - its resistance should be close to 0 Ohms.

Step 3: Typical faults and their elimination

Most of the breakdowns of Xiaomi power supply comes down to several scenarios.

1. The unit is not turned on (no output voltage)

Reasons:

• 🔌 Breakdown of the network filter or diode bridge – check the diodes 1N4007 similar.
• 💥 Failure of the power transistor (usually) MOSFET type 6N60 or 7N60).
• 🔋 Controller malfunction (e.g., chipset) BP2832A model USB-PD).

Solution: Replace burnt-out elements. Transistors and diodes can be soldered with a blow-out soldering iron, and new ones can be installed polarly. Controllers are usually not repaired, it's easier to buy a donor board.

2.The unit is heated or disconnected under load

Reasons:

• 🔥 Dry electrolytic capacitors - replace with new ones with the same capacity and voltage (for example, 1000µF 16V).
• 🧹 Radiator pollution – clean the dust with a brush and replace the heat paste.
• 🔄 Failure of feedback (optron) PC817 or resistors around it).

3. It's not working. USB-port (undefined device)

Reasons:

• 🔌 Breaking tracks - restore with lintels from thin wire.
• 🔋 Controller failure USB-PD (for example, CYPD3177 block-wise 65W).
• 🛡️ Close in the output capacitors - check 10µF/25V capacitors USB-plug.

Important: If you replace capacitors, take low-capacitor models ESR (For example, the Nichicon series. UHE Panasonic FC). Xiaomi power supplies often use capacitors with an operating temperature of 105.°C – don’t skimp on quality!

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Before soldering new components, clean the contact areas with alcohol or flux cleaner. Remains of old solder can cause cold soldering, which will lead to repeated breakage.

Step 4: Assembly and testing

Collect the power supply in reverse order, watching for:

• 🔧 The correct position of all latches and seals (for example, in Xiaomi) 20W There is a silicone pad for tightness).
• 🔌 The tight fit of contacts is especially important for USB-plug.
• 🧲 Absence of unnecessary screws or parts (check the photos taken before disassembly).

After assembly, connect the unit to the network through the incandescent lamp 40–60W, This will protect you from short circuits in case of possible assembly errors. If the lamp does not light up, the unit is working. If the lamp is burning at full incandescent, the inside is short circuit, you need to re-disassemble and check the installation.

Then check the output voltage with a multimeter:

• For 5V/2A blocks (e.g. Mi Charge) 10W) — must have 5.0V ± 0.2V.
• For USB-PD blocks (e.g. Xiaomi) 65W) — voltage varies 5V before 20V depending on the connected device.

⚠️ Warning: If the power supply after repair works, but is very warm, check the heat paste on radiators. in Xiaomi GaN models (for example, 120W HyperCharge) uses a special paste with high thermal conductivity - ordinary silicone will not work.

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Never turn on the power supply without a load (without a connected device) – this can disable the feedback circuits and the controller. USB-PD.

Upgrading the power supply Xiaomi

If you disassembled the unit not for repair, but for upgrades, here are some popular modifications:

• 🔋 Replacement USB-Type-C port (e.g., older Micro-USB models) will require a controller soldering CYPD3177 resistor CC1/CC2.
• 🔌 Increased power (e.g., with a 18W before 30W). To do this, you need to replace the transformer, power transistor and output capacitors, as well as reflash the controller (if it is programmable).
• 🛡️ Installation of additional protections (waristors, thermistors) to improve reliability.
• 🔄 Modding of the housing – for example, installing a fan for active cooling (relevant for blocks) 65W+).

Example: in the Xiaomi block 20W replace USB-Type-C port, adding resistors 5.1kOm support USB-PD. However, it requires skills to work with SMD-Components and soldering station with temperature control.

Warning: Modifications can result in a loss of warranty, overheating or even fire if made incorrectly.

Frequent Mistakes and How to Avoid Them

Even experienced craftsmen sometimes make mistakes when disassembling Xiaomi power supplies.

1. Use of metal tools to separate the shell → scratches, chips, latch damage. ✅ Solution: Use only plastic mediators.
2. Overheating of the fee by a hairdryer → scaling off of tracks or melting of components. ✅ Solution: Keep the hair dryer 10cm away and don't heat one dot longer than 10 seconds.
3. Forgetting to discharge the capacitors → shock or multimeter failure. ✅ Solution: Always discharge the capacitors with a screwdriver with an insulated handle.
4. Use of excessive force in the despatch of components → severance. ✅ Solution: Use a solder removal braid and a temperature adjustable soldering iron (maximum 350)°C).
5. Incorrect assembly (confused wires or boards) → short-circuit. ✅ Solution: Check with photos taken before disassembly.

Another common problem is the loss of screws or springs. Xiaomi blocks often use screws of different lengths (for example, in Xiaomi). 65W GaN has 3mm and 5mm screws. If you lose your fastener, don't replace it with the first one you find - too long a screw can damage the board.

FAQ: Answers to Frequent Questions