Disassembly of the screwdriver Xiaomi Mijia: detailed instructions with photos and repair tips

The Xiaomi Mijia electric screwdriver (WSDCG QDC01FM, WSDCG QDC02FM and its counterparts) has become a popular tool among home craftsmen because of its compactness, power and convenience. However, like any technique, it can fail: it stops holding a charge, does not rotate a bat or makes extraneous sounds. In most cases, the problem can be solved by yourself - this will require disassembling the case, checking internal components and replacing defective parts.

In this article, you will find step-by-step instructions for disassembling photos of key steps, a list of necessary tools and tips on how to avoid typical errors. We will also discuss which hidden mounts often overlook newcomers, and how to properly remove the battery without damaging contacts. If you have never disassembled a power tool, do not worry: the Mijia design is simpler than professional screwdrivers, and with careful approach, the risk of breaking something is minimal.

Preparation for disassembly: tools and security measures

Before you start, make sure you have everything you need, and without the right tools, you risk scratching the body, tearing off the screws, or damaging the interior parts, and here's the minimum set you'll need:

• 🔧 Set of screwdrivers (cross-haul) PH00, flat 2.0 mm, hexagon 1.5 mm - for some models).
• 📸 Smartphone or camera – to fix each stage of disassembly (useful when reassembling).
• 🧲 Magnetic mat or bowl – so as not to lose small screws and springs.
• 🔥 Hair dryer or plastic blade - for neat opening of latches (if the body is glued together).
• 🔋 Multimeter – to check battery voltage and circuit integrity.

Pay special attention to safety:

• ⚡ Disconnect the screwdriver from the charger at least 12 hours before disassembly - this will eliminate the risk of short circuit.
• 🧤 Work with gloves if you plan to touch the board - static electricity can damage the chips.
• 👓 Use a magnifying glass or magnifier to inspect small parts (such as battery contacts).

⚠️ Note: If your Xiaomi Mijia screwdriver is warranty, disassembly will cancel it. Check the date of purchase in the check or in the Mi Home app - it may be cheaper to contact the service center.

Step 1: Remove the back cover and remove the battery

Start by inspecting the body. Most Mijia models have a 4-6 cross screw (PH00) back cover, and the screws can be hidden under stickers or rubber legs, gently tucked into a plastic blade.

Once the screws are removed, the lid is usually removed effortlessly, but sometimes it is held by hidden latches to avoid breaking them.

1. Place the screwdriver in the gap between the halves of the body closer to the handle.
2. Carefully turn the tool like a lever to separate the latches around the perimeter.
3. If the cover does not lend itself - warm it with a hair dryer (temperature not higher than 60 ° C) to soften the glue.

Under the lid, you'll see a battery (usually 3.7V 2000mAh) soldered or connected through a connector. Never pull the wires -- first disconnect the connector with a flat screwdriver, then remove the battery. If the battery is swelling, don't try to repair it! Dispose of it according to local regulations.

Step 2: Disassembly of the mechanical part and access to the motor

Once you remove the lid and the battery, you'll have access to the mechanical screwdriver stuffing, so you need to take your time and take your time.

1. Remove the cartridge (if it's removable). In Mijia, it's usually locked with a locking ring -- put it in a screwdriver and turn counterclockwise.
2. Remove the plastic gearbox. It's attached to 2-3 screws and can be covered with lubrication. Don't lose the gears!
3. Get to the motor. It's mounted on a metal plate with shock absorbers, unscrew the screws and carefully remove the engine without pulling the wires.

Note the brush assembly (if your model has one) and some versions of the Mijia have a brushless engine, but in older batches there are graphite brushes, and if they're worn down to 50 percent of their original length, they need to be replaced.

⚠️ Warning: If you hear a crunch or a grinding hand when you're rotating the gear, it's a sign that the gears are broken. Don't turn on the screwdriver in this condition, because metal shavings can damage the engine.

Step 3: Diagnostics and repairs of the control board

The control board is the brain of the screwdriver, and it's responsible for adjusting speed, overheating, and communicating with the start button.

1. Unscrew the screws that attach the board to the case (usually 3-4).
2. Carefully disconnect all connectors, having previously photographed their location.
3. Check the board for blackened elements, swollen capacitors or oxidized tracks.

Typical fee problems:

• 🔥 Burned. MOSFET-Sign: the screwdriver is not turning on, but the charging indicator is on.
• 📉 Faulty charge controller (usually) TP4056 Sign: battery is not charging.
• 🛠️ Oxidized contacts of the start button, sign: screwdriver is jerking or spontaneously switched off.

For the repair of the fee you will need:

• 🔬 A soldering iron with a thin sting (power not more than 30 W).
• 🧵 solder and flux (better to use acid-free).
• 🧴 Alcohol to clean board from flux residues.

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If you are not sure about your soldering skills, order a board repair in the service. The cost of replacing a transistor or controller rarely exceeds 1000-1500 rubles, while a new screwdriver will cost 3-5 times more expensive.

Step 4: Cleaning and lubricating the gearbox

The gearbox is one of the most loaded parts of the screwdriver, and over time, the lubricant dries out and the gears wear out, and to extend the life of the tool, it is recommended that the gearbox be cleaned and lubricated every 1-2 years (or after 50 to 100 hours of active use).

Procedure:

1. Disassemble the gearbox by removing all the gears and bearings, wash them in kerosene or WD-40, then dry them with compressed air.
2. Check the gear teeth. If they're chipped or badly worn, replace the part (you can order from AliExpress by the screwdriver model number).
3. Apply lithium or silicone lubrication to all rubbing surfaces. Don't use solidol or graphite lubrication - they thicken quickly!

It is convenient to use a needle syringe to lubricate the bearings. Apply the lubrication point-by-point, avoiding getting into plastic parts - this can cause them to deform.

Step 5: Reverse Assembly and Testing

Building a screwdriver after repair is as important as disassembling.

1. Check all the sealing rings (if you have them in your model) and the damaged rings can cause dust to enter the body.
2. Twisting the screws cross-cross to avoid skewing the lid. Don't put too much effort into it, you can rip the thread.
3. Before final assembly, plug in the battery and check the screwdriver without the lid, so you can quickly fix problems if they occur.

After assembly, perform the test:

• 🔋 Check the charge indication (all segments must burn if the battery is charged).
• 🔄 Make sure the reverse (switching the direction of rotation) is working correctly.
• 🛠️ Drill the test hole in a soft material (such as wood) at different speeds.

⚠️ Warning: If the screwdriver warms up more than usual after assembly, immediately disassemble it again. Probable reasons: wrong gearbox assembly, twisted screws or short circuit on the board.

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The most common assembly error is the incorrect positioning of the sealing ring between the body and the cartridge, which leads to backlash and rapid wear of the gears. Always check the photos taken before disassembly!

Common Mistakes and How to Avoid Them

Even experienced craftsmen sometimes make mistakes when disassembling Xiaomi Mijia, and here are the most common ones and ways to prevent them:

• 🔩 Use a magnetic screwdriver and don't put too much effort into it. WD-40 And wait 5 minutes.
• 🔌 Damaged connectors. Never pull the wires, always pull the connectors with a plastic blade.
• 🔥 Overheating the board when soldering. Use a soldering iron with a power of no more than 30 W and work with short touches (no longer than 2-3 seconds).
• 🧲 Lost parts. Magnetic mat and screw containers are your best friends. Sign containers (e.g., cartridge screws, gear gears").

Another common problem is the wrong diagnosis, for example, if the screwdriver doesn't turn on, many people blame the battery right away, but the reason may lie in:

• Oxidized contact of the start button.
• The wire break between the board and the motor.
• Faulty. MOSFET-transistor.

To save time, use the exclusion method:

1. Check the battery with a multimeter.
2. Make sure that the charge is served power (measure the voltage on the contacts).
3. Ring the chain from the button to the motor.

FAQ: Frequent questions about the dismantling of Xiaomi Mijia