The Xiaomi Mijia S300 has proven to be a reliable daily shave device that combines affordable price and functionality. However, like any mechanical appliance, it requires periodic maintenance, especially if you notice a decrease in shave quality or foreign sounds when working. Owners often wonder whether self-disassembly of the case is possible to deep clean or replace worn components.
Unlike the simpler models, the S300 design involves tight assembly using sealing pads to protect against moisture according to IPX7.This means that the dismantling process requires accuracy and understanding of the sequence of actions so as not to damage the rubber seals and not to disturb waterproof. Incorrect opening can lead to moisture entering the engine, which will cause corrosion of the contacts.
In this article, we will take a detailed look at the Mijia S300 trimmer’s safe disassembly algorithm. You will learn what tools you will need, how to properly remove the cutting unit for sharpening or replacement, and how to clean the internal cavities of accumulated dust and hair.
Tools and workplace preparation required
Before you start disassembling the Xiaomi electric razor, you need to organize a clean and well-lit workspace. Dust, villi or small parts that fall on the floor can cause problems when building, so it is recommended to cover the table with white cloth or use a special antistatic mat. The lack of static electricity is critical to the safety of electronics, even if you do not plan to touch the board directly.
The razor design does not require complex tools, but the use of inappropriate items can lead to scratches on the body or licking of the screws. The main element of fixation here are screws with a hidden head, which are often found in modern portable technology. To twist them, you will need a special screwdriver, the size of which should be perfectly consistent with the screw to avoid damaging the metal.
It is also worth preparing a container for folding small parts so that nothing is lost in the process of work. Plastic cards or thin metal blades will help to gently separate the halves of the body without damaging the latches. It is important that all tools are dry and fat-free, as the residue of technical lubrication or dirt can get into the bearings of the engine.
- 🔧 Torx screwdriver T5 or T6 (depending on the batch) for the twisting of fasteners.
- 🧤 Thin plastic blade or mediator for opening the body without scratches.
- 🧼 Isopropyl alcohol and lilaless wipes for cleaning internal components.
- 🛢️ Special oil for lubricating razor knives and engine bearings.
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Use a magnetic tray or piece of paper with sectors drawn to remember which screw was twisted from where, as their length may vary slightly.
Dismantling of cutting unit and grid
The first step in any maintenance is to remove the outer working part of the device. In the Mijia S300, the cutting unit is attached to the body using a rotary mechanism or locks, depending on the modification of the head. Before removing, you need to make sure that the device is turned off, although mechanical locking usually prevents accidental start with the disassembled body.
Carefully press the locks on the sides of the head and pull the block up. Don't use excessive force, as plastic latches can be brittle, especially if the razor has been used for a long time in conditions of temperature changes. If the head is removed tightly, you can slightly turn it counterclockwise to unlock the lock.
Once you remove the main unit, you'll have access to the inner mesh and the rotary knives, and this is where most of the cut hair and skin fat is stored, which leads to a decrease in the efficiency of shaving, and for deep cleaning, this knot must be completely dismantled by disconnecting the fixing elements that hold the mesh on the frame.
⚠️ Attention: The cutting edges of the knives are extremely sharp. When removing the net and rotors, be extremely careful not to hurt your fingers.
Check the grid condition for microcracks or scuffs. If you see through holes or severe deformities on the metal surface, you can't continue to operate without replacement, as this will cause skin injuries and engine failure due to increased friction.
Disassembly of the main body of the device
To access the engine and battery, you need to divide the main tube of the body into two halves. At the bottom of the device, closer to the Type-C charging port, mount screws are often hidden, and they can be closed with a decorative cap or rubber lining, which you need to gently fit with a blade or needle.
Once all the visible screws have been unscrewed, the body is held by plastic latches around the perimeter. Use a plastic blade to walk along the junction of the halves, sequentially snapping the locks. Movements must be progressive, without jerking, so as not to break the plastic ears of the fasteners, which, after repair, may not keep the sealed.
Inside the case, you'll see a cylindrical engine, a control board and a battery pack. Pay attention to the location of the wires connecting the engine to the board. In some versions of the Xiaomi S300, the wires can be soldered, in others they are connected through a connector. Sharp jiggling of the body halves can lead to the breakage of thin power conductors.
☑️ Check before complete disassembly
If you're only looking at lubricating the engine, you don't need to remove the board completely, you just need to access the end of the motor, but you have to remove the electronics from the plastic tube to replace the battery or repair the power button.
Engine maintenance and pollution removal
The heart of a razor is a vibratory or rotary motor, which over time becomes overgrown with fine metallic dust and hair. These abrasive particles enter the shaft gaps and accelerate the wear of the bearings. To clean, you need to gently blow the insides with compressed air or use a soft brush.
The use of engine flushing fluids is strongly discouraged unless you are sure they will dry out completely. The moisture residue will cause the windings to oxidize and short circuit; it is better to use isopropyl alcohol, which evaporates quickly and degreases the surfaces without leaving a conductive layer.
After mechanical cleaning, you have to lubricate the moving parts, a drop of special oil is applied to the engine axle and the inner surface of the bushings, and the excess lubrication must be removed, because when it is working, it can spray and get on the board contacts, which will worsen their conductivity.
| Component | Type of pollution | Cleaning method | Frequency of service |
|---|---|---|---|
| Cutting knives | Hair, skin fat | Water washing, brushing | After each use |
| Filter net | Fine dust, powder. | Air purge, dry cleaning | Once a week. |
| Motor bearings | Metal shavings | Lubrication, purge | Every 6-12 months |
| Charging port | Oxygens, dust | Dry cotton swab, alcohol | When you have problems with charging |
Why does the engine hum after cleaning?
Battery Replacement and Electronics Diagnostics
Reduced battery life is a common cause of disassembly of the Mijia S300. Inside the device is a lithium-ion battery, which eventually loses capacity. To replace it, you need to carefully solder the old element and solder the new one, observing polarity. An error in the connection of the plus and minus will cause the board to instantly fail.
When working with a soldering iron, it is important not to overheat the adjacent components on the board. Use a soldering iron with a thin sting and a temperature of about 300-350 degrees. Before soldering, it is recommended to fix the wires so that they do not twitch during operation. The new battery should have the same dimensions and voltage, usually 3.7V.
If the razor stops turning on, the problem may not be the battery, but the power button. The mechanical contact under the button will eventually oxidize or fall off. It can be cleaned with alcohol or gently pressed with tweezers. In the event of a break in the contact, you will need a jumper or a microswitch.
⚠️ Attention: Lithium batteries are sensitive to punctures and overheating.Do not try to disassemble the battery itself or heat it with an open fire, this can cause fire.
Once the components are replaced, put the device back together and check the work. Primary charging should be monitored to prevent the housing from heating or the new battery from bloating. If the device is working correctly, you can proceed to final sealing.
Assembly and seal check
The final step is to assemble the case and restore the waterproof. When you connect the halves, make sure that the rubber seal lies right in its groove around the perimeter. No creases or skews are allowed, otherwise the declared IPX7 protection will not work, and water entering during washing will be fatal.
Twisting the screws cross-cross, evenly pressing the halves of the body, this will avoid distortion and the appearance of gaps. Do not drag the screws, because the plastic in the place of the thread can burst, which will make further use impossible.
Once assembled, do a leakproofness test, wrap the razor with a dry napkin and put it in the water for a few seconds, then check the napkin for moisture. If everything is dry, you successfully disassembled and assembled the Xiaomi Mijia S300. Now the device is ready for efficient operation again.
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Quality assembly depends on the condition of the sealing gum – if it has lost elasticity, replace it or use a thin layer of silicone sealant.