Step-by-step analysis of Xiaomi Redmi 9 Pro: from the back cover to the motherboard

Xiaomi Redmi 9 Pro is a popular 2020 model that is still in high demand due to its balanced performance and affordable price, but over time, even the most reliable device can require repairs, from replacing the battery to cleaning the connectors or recovering from a fall.

In this article, we will take a closer look at the Redmi 9 Pro disassembly process, focusing on each step from removing the back cover to removing the motherboard, what tools will be needed, how to avoid common errors (such as damage to the fingerprint scanner plume), and what to do if something goes wrong, and the instructions are suitable for beginners and experienced craftsmen who want to refresh their knowledge of a particular model.

Before you start, consider that self-disassembly will void the Xiaomi warranty if it is still valid, and there is also a high risk of damage to components if you do not act neatly — especially for flexible plumes and microphone modules. If you are not confident in your abilities, you should contact the service center.

Preparation for disassembly: tools and security measures

Before you disassemble the Redmi 9 Pro, gather everything you need. The absence of even one tool can lead to irreparable consequences - for example, using an inappropriate screwdriver will damage the screws, and the absence of a suction cup will make it difficult to remove the back cover.

Here is the minimum set you will need:

• 🔧 Plastic mediators (2-3 pc.) - for careful liding and separation of adhesive joints.
• 🔩 Screwdriver kit: cross-haired PH00 (for shell screws) and five-pointed Pentalobe P2 (screw-tray SIM).
• 🧲 Magnetic mat or screw container – to avoid losing small details.
• 🔥 Dryer or thermo-air station - for softening the glue (temperature not higher than 80)°C!).
• 📱 Suction (diameter) 5-7 cm) - will help to lift the back cover after heating.
• 🔍 Loop or magnifying glass - for inspection of small contacts and plumes.
• 🧴 Isopropyl alcohol (90%+) — Cleaning contacts and removing glue residues.

Also, prepare your workspace: it should be well lit, without dust or static electricity. Work on a soft-backed table (like a silicone mat) to avoid scratching the case. If you plan to replace the battery, buy a new adhesive-based module in advance - the original batteries for the Redmi 9 Pro have the articula MBJ4265 (4000 mAh).

⚠️ Warning: Do not use metal tools to lid the lid - they leave scratches and can damage the antenna tracks inside the enclosure. Also avoid overheating with a hairdryer: if the temperature exceeds 90°C, the glue can dry even more, and the display can peel off.

Removal of the back cover: technique and typical errors

The Redmi 9 Pro's back cover is attached to the glue and latches around the perimeter, and the challenge is not to damage the antenna tracks, which are close to the edges. Start with the power outage: turn off your smartphone completely and remove the tray. SIM-cards (use a paper clip or special key).

Follow the step-by-step instructions:

1. Heat the cover. Evenly warm the back panel with a hair dryer for 2-3 minutes, keeping it at a distance of 5-7 cm Temperature - 70-80 ° C (not higher!). Pay special attention to the edges.
2. Suctioning with a suction cup. Stick the suction cup closer to the bottom edge (where the Type-C connector is located) and pull up. If the lid doesn't lend itself, repeat heating.
3. Careful compartment. Put a plastic mediator in the gap, and slowly drive it along the edge, separating the latches. Take your time, the resistance will be stronger at the corners.
4. Check the antenna tracks. After removing the lid, inspect the inside of the lid, and if you see damaged copper tracks, it will degrade the Wi-Fi and cellular signal.

If the lid doesn't lend itself, don't use excessive force -- you better warm up the problem area again. A common mistake of beginners is trying to put the lid on with a knife or a screwdriver, which leads to chipped plastic or cuts in the hands.

Disconnecting the battery and removing the motherboard

When you remove the back cover, first thing you do is turn off the battery.

1. Find the battery connector on the motherboard (usually black with an orange or red marker).
2. Carefully tuck the connector into a plastic pickup or tweezers, pulling up. Don't pull the wires!

Now you can start removing the motherboard. In the Redmi 9 Pro, it's mounted on 12 screws of different lengths -- remember the location of each one so you don't get confused when you build it, and you're advised to take a picture of the board before you extract it, or make a diagram.

Procedure:

1. Unscrew all screws (use the PH00 magnetic screwdriver).
2. Disconnect the plumes: 📱 Display module (the widest connector). 🔍 Fingerprint scanner (thin flexible plume). 🔊 Speaker and microphone (small white connector).

Carefully raise the fee with a plastic shoulder blade, starting at the top edge. Be careful - under the payment may remain unnoticed plumes!

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If the screw is "stiff" and does not twist, drop a little isopropyl alcohol on it and wait 1-2 minutes. This will help dissolve the oxides and facilitate unscrewing.

⚠️ Attention: At Redmi 9 The fingerprint scanner's plume is extremely fragile. ID will stop working and the replacement of the plume will cost 30-50% Always unplug it last and fix the charge with your hand when you remove it.

Battery replacement: nuances and the choice of a new module

The battery in the Redmi 9 Pro has a capacity of 5020 mAh (typical - 4850 mAh) and is attached to double-sided tape. To replace you will need a new battery with adhesive base (for example, the original MBJ4265 or analogues from Baseus, Remax).

• 🔥 Hazel-softening.
• 🧊 Plastic card or mediator for tampering with the battery.
• 🧴 Isopropyl alcohol for removal of glue residues.
• 📏 Double-sided tape or glue tape (if it is not included with the battery).

Replacement process:

1. Warm up the battery with a hair dryer (temperature - 60-70 ° C) for 1-2 minutes.
2. Carefully tuck the battery with a plastic card from any angle, trying not to puncture it.
3. Slowly separate the module, pouring alcohol under it to dissolve the glue. Don't pull sharply - the risk of breaking the battery!
4. After extraction, clean the seat from glue residues with alcohol and a napkin.
5. Set the new battery, press it for 10-15 seconds to fix the glue. Connect the connector to the board.

After replacing the battery, be sure to calibrate the charge controller:

• Charge your phone to 100% and leave it on charge for another 1 hour.
• Turn off the charging and discharge until it is automatically turned off.
• Repeat the cycle 2-3 times.

Phone turns on without charging | Charging is stable (no jumps %) | Battery is not swelled (check visually) | Battery time corresponds to the declared-->

Disassembly of the display module and screen replacement

Redmi screen 9 Pro is a prefabricated module that includes IPS-Replacing the screen requires special care, because the display plume is very thin and easily breaks. If you have vertical stripes, artifacts when touching or broken pixels on your phone, you will most likely need to replace the module (the original articula — 2204-000015).

Procedure:

1. Warm up the display around the perimeter with a hairdryer (70°C) for 3-4 minutes.
2. Subdue the screen with a plastic mediator, starting at the bottom edge (where the Type-C connector is located).
3. Slowly separate the module, making sure you don't break the plume. In the Redmi 9 Pro, it's located at the top.
4. Disconnect the plume from the motherboard by pulling the black tongue of the connector.
5. Install a new screen, plug in the plume and check the operability before the final assembly.

If you have problems with the sensor after changing the screen, check:

• 🔌 Is the sleeve properly connected (it should sit tightly, without distortions).
• 🧹 Is there any dust or debris in the connector.
• 🔄 Try reconnecting the plume. 2-3 once.

⚠️ Attention: When changing the screen in the Redmi 9 Pro, there is often a problem with "ghost touches" - when the phone spontaneously responds to presses. This is due to poor contact of the plume or damage. → Display. → Screen calibration) does not help, you will need to replace the plume.

Cleaning connectors and recovery after moisture

If your Redmi 9 Pro gets caught in rain or falls in water, don’t turn it on right away – it can cause a short circuit.

1. Turn off your phone (if it still works).
2. Remove the tray. SIM-Cards and battery (if you have experience disassembling).
3. Wet the moisture with a napkin and leave the phone in a dry place for 24-48 hours.

For deep cleaning of connectors will require:

• 🧴 Isopropyl alcohol (90%+) — corrosion-dissolving.
• 🪥 Toothbrush with soft bristles - for cleaning contacts.
• 💨 A cylinder with compressed air - for blowing out dust.

Pay particular attention to:

• 🔌 Type-C connector (often oxidized after moisture is ingested).
• 📶 Antenna contacts under the back cover.
• 🔋 Battery connector on the motherboard.

After cleaning, let the phone dry for another 12 hours before turning on, and if the device doesn't turn on or is not working smoothly, the motherboard is likely damaged, in which case a diagnosis will be required at the service center.

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Even if the phone is turned on after moisture is injected, the consequences can occur later: contact corrosion, failure of the microphone or speaker.

Assembly of the phone: procedure and testing

The Redmi 9 Pro should be assembled in reverse order, but with a few nuances in mind:

1. Before installing the back cover, check that all plumes are tightly connected and the screws are twisted.
2. Apply a new adhesive layer on the lid (you can use double-sided 3M 9448A tape).
3. Press the lid evenly around the perimeter, starting at the top edge.
4. Warm up the edges with a hair dryer (50°C) for 1-2 minutes for better fixation.

After assembly, be sure to test all the functions:

• 📶 Cellular network signal and Wi-Fi.
• 🔋 Charging (check if the percentage is “up).
• 🎤 Microphone and speaker (record voice message).
• 📷 Cameras (front and main).
• 👆 Touch screen and fingerprint scanner.

If something is not working properly, take the phone apart again and check:

• Connecting plumes (especially the display and battery).
• No locks on the motherboard.
• Integrity of antenna tracks on the back cover.

Frequently asked questions