Disassembly Xiaomi Redmi Note 9: a complete guide with photos and tips from the master

The Xiaomi Redmi Note 9 is one of the most popular smartphones in the budget segment, but even it is not immune to breakdowns. Disassembly of the device may be necessary to replace the battery, repair the display or clean the dust. However, the wrong actions can turn simple repairs into expensive. In this guide, we will detail the process of disassembling the Redmi Note 9 (codenamed merlin), focusing on each step from tool preparation to removal of the motherboard.

It's important to understand that disassembling a smartphone will void the warranty (if it's still valid) and require care. Inside the case, you'll find brittle plumes, duct tapes, and miniature screws that are easy to lose. Not only will we show you how to disassemble the device, but we'll also warn you of common mistakes that beginners make, such as why you can't put a knife on the lid or how to avoid damaging the battery's flexible plume.

This article is for self-repair and for those who want to understand the inside of a smartphone, and we used original parts and professional tools, but we adapted the instructions for the home, and if you've never taken a smartphone apart, don't worry: our guide is for beginners, with step-by-step photos and explanations of each action.

Preparation for disassembly: tools and security measures

Before you start disassembling the Redmi Note 9, make sure you have everything you need, and even missing one tool can damage the body or internal components.

• 🔧 Set of screwdrivers (cross-haul) PH00, flat 1.5 mm, five-pointed Y00 screw-tray SIM-map).
• 📱 Plastic mediators or shoulder blades (metal tools scratch the body!).
• 🔥 Dryer or thermo-air station (to soften the glue under the back cover).
• 🧲 Magnetic mat or container (to avoid losing screws).
• 🔋 Screen suction cup (helps to lift the display module).
• 📦 Isopropyl alcohol (90%+) (Cleaning contacts and removing glue residues).

Also, prepare your desk: clean, well-lit, and without static electricity (ideal for an antistatic bracelet); Never disassemble your smartphone on a carpet or couch: static electricity can damage the motherboard; if you don't have experience, practice on an old phone or watch video disassembly, this will help avoid typical mistakes.

⚠️ Warning: Before disassembling, completely discharge the battery (up to 0%) and leave it in this state for 1-2 hours. This minimizes the risk of short circuit in case of accidental battery damage. If the battery is swollen, do not disassemble the phone yourself: contact the service center!

Removal of the back cover: how not to damage the body

The Redmi Note 9's back cover is glued around the perimeter, so it needs to be heated carefully to soften the glue. Use a dryer at minimum power (temperature ~60-70°C) and warm the edges of the body evenly for 2-3 minutes. Don't direct hot air to one place for too long - this can warp the plastic.

After heating, take a plastic blade and start pulling the lid on the bottom edge (near the USB-C connector). Put the mediator in at least 2-3 mm deep and slowly lead along the body. You hear the characteristic clicks - these are the latches detached. If the lid does not respond, warm up the problem area again.

• 🔥 Don’t use metal tools – they leave scratches.
• 🚫 Do not apply force: if the lid is not removed, then the glue has not softened sufficiently.
• 📍 Start at the bottom edge – there are fewer plumes and the risk of damage is minimal.

When you take the lid off, you'll see the battery, the motherboard, and some plumes. Don't pull the lid abruptly, it might be stuck to thin antenna wires or a fingerprint scanner plume. Disconnect them carefully if they're stuck. NFC-antenna (thin metal band under the lid) – it is easy to tear.

Battery shutdown: why it's critical

Before touching any components inside your smartphone, be sure to turn off the battery. Even if the phone is turned off, there is residual voltage left on the board, which can damage it if short-circuited. In the Redmi Note 9, the battery connector is located at the top of the motherboard and closed with a black insulating tape.

Carefully tuck the tape with your nail or plastic spatula and bend it away. Under the tape you'll see a small white connector with an orange or red wire, which is the battery connector. To disconnect it, put it in a plastic tool (metal can close the contacts!) and gently lift it up. Make sure the connector is completely out of the socket.

⚠️ Attention: If you accidentally touch tweezers or screwdrivers to the contacts of the battery when the battery is connected, it can lead to fire. Always check if the connector is turned off before working with the board!

Once the battery is turned off, you can start removing the motherboard or other components, but remember that some plumes (like the display or the cameras) are very fragile. If you're not planning on replacing the battery, don't take it out completely -- just turn it off.

Removal of the motherboard: step-by-step instructions

The Redmi Note 9 motherboard is mounted on multiple screws and connected to other components through plumes, and to remove it, follow the following steps:

1. Unscrew all the screws around the board (about 10-12 of them). Use a magnetic screwdriver to keep the screws from getting lost. Remember where the screw was, they can vary in length!
2. Disconnect all the plumes: Display plume (top of board, under metal screen), camera plumes (back and front), fingerprint sensor plume (if you have one in your modification), USB-C charging connector plume.

Carefully raise the fee

Once you remove the board, you'll see the back of the memory chips, the MediaTek Helio G85 processor, and other elements. Don't touch them with your hands, static electricity can damage the chips. If you want to clean the board of dust, use a soft brush and isopropyl alcohol (apply to a cotton swab, not a board!).

💡

If you're taking a replacement motherboard, take a picture of its location before the screws are unscrewed, which will help you put the phone back together properly, especially if the screws are of different lengths.

Replacement of the battery: nuances and errors

The battery in the Redmi Note 9 is one of the most vulnerable parts, and it gets swollen over time, loses capacity, or refuses to hold charge, and battery replacement is the most common reason for this smartphone to be disassembled, but there are some critical issues:

• 🔋 Only original battery or certified equivalent (e.g., from the ZMI Cheap batteries may not meet the declared capacity or swell in a month.
• 🔥 Don't puncture an old battery - even if it's swelling. Lithium-ion batteries can ignite if damaged.
• 🧴 Use a special glue to fix the new battery (for example, B-7000). Double-sided tape does not provide reliable fastening.

Replacement process:

1. Turn off the battery connector (as described above).
2. Heat the body with a hairdryer to soften the glue under the battery.
3. Carefully tuck the battery with a plastic spatula from any edge. Don't try to pull it out right away, puff it up gradually, adding isopropyl alcohol to dissolve the glue.
4. Install a new battery after clearing the landing site of glue residues. Connect the connector and check if the battery is recognized by the system (turn on the phone).

⚠️ Warning: If the battery is not turned on after the battery is replaced or it shows 0% charge, check: Is the connector correctly connected (sometimes it is not fully inserted); is the battery plume damaged (see for breaks); does the new battery meet the original parameters (voltage must be) 3.85V, Capacity: 5020 mAh).

💡

When replacing the battery, never use metal tools to tamper with the battery, which can puncture the battery and cause fire. Always work with plastic blades and with safety glasses.

Phone Assembly: How to Avoid Mistakes

Putting the Redmi Note 9 back together is often harder than disassembling, with the main problem being forgotten screws, misconnected plumes, or a skewed lid. Here's a checklist for a successful build:

Pay particular attention to:

1. The display plume -- it has to be plugged in before the motherboard is fixed with screws, and if you pin the board earlier, the plume can bend.
2. Wi-Fi and NFC antennas, they often stick on the lid, make sure they're flat and not twisted.
3. Volume and power buttons, check them to full assembly, and if the button doesn't press, you may have forgotten to install the silicone pad.

After assembly, turn on the phone and check:

• 📶 Does the sensor and display work.
• 🔊 Is there sound in the speaker and microphone.
• 📷 Are the cameras (front and back) functional).
• 🔋 Is the battery charge correctly determined.
• 🌐 Is it network and Wi-Fi.

If something doesn't work, don't panic. Take the phone apart and check the appropriate plumes, and 90 percent of the time, the problem is a loosely inserted connector.

Frequent problems after disassembly and their solution

Even with careful disassembly, there can be problems, and here are the most common ones and how to fix them:

If you have all the connectors checked, you may have a problem with the motherboard, and then you should go to the service center, and don't try to solder the board yourself without experience, because that can make things worse.

FAQ: Answers to Frequent Questions