Checking used Xiaomi smartphone: step-by-step instructions for safe purchase

Buying a used Xiaomi smartphone is a great way to save money, but without careful testing, the risk of running into a “cat in a bag” is extremely high. According to statistics, one in three devices on the secondary market has hidden defects, from a bloated battery to a replaced one. IMEI. This article will help you avoid common mistakes and identify problems before transferring money.

We will analyze not only basic checks (screen, case, cameras), but also hidden threats that sellers are silent about: software locks, repair traces, battery wear and even fakes for the original Redmi models or even fakes. POCO. Special attention will be paid to Xiaomi’s branded chips, which are often ignored during inspection, for example, work. IR-Port or state of LiquidCool in gaming smartphones.

Important: the instruction is relevant for all the brand lines - from the budget Redmi Note to the flagship Xiaomi 14. But if you buy a model older than 2020, note that some tests (for example, checking the price of the product) 5G-modems) may be irrelevant.

1. External inspection: what gives the “broken” smartphone

Start with a visual check, which will take 5 minutes, but will immediately show how carefully you treated the device. 5000K), Artificial light can hide scratches.

Pay attention to:

• 🔍 Body and frame: Microcracks on speakers or buttons indicate falls. On aluminum models (Xiaomi 12 Pro, Mix 4), check if the angle is bent - this is a sign of a strong impact.
• 📱 Screen: swipe your finger across the glass – if you feel the “steps”, this is a sign of glass replacement (often after such a procedure, the oleophobic coating is lost).
• 🔋 Rear cover: on models with glass panel (Redmi) K50, POCO F5) Check if there is a “web” around the cameras – it is a consequence of the impact.
• 🔌 Connectors: Insert charging cable into USB-C — If it dangles or enters only at an angle, the port will soon fail.

You're going to have to pay attention to the buttons. Press the Power and Volume 10 to 15 times in a row, and if one sticks or creaks, it's a sign of moisture or wear. IP53 (For example, Redmi Note 12) check the rubber plugs on the sim-lot - if they are missing, the protection against dust is broken.

⚠️ Warning: If there are traces of glue on the case or uneven gaps between the screen and the frame, this is 100% an autopsy sign.

2 Screen check: tests for broken pixels and "yellow" spots

The display is the most expensive component to repair, so you can take the time to check it.

1. Open a black background (like the Display Tester app or the DisplayTests website) and look carefully at the screen from an angle — white or colored dots are dead pixels.
2. Switch to a white background – this is how dark spots are visible (often appear after falls).
3. Check Gradients (Gray background): If bands or "waves" are noticeable, it is a matrix defect (OLED-Xiaomi 13 screens are particularly affected by this).

For AMOLED-displays (Redmi) K60, POCO X5 Pro) burnout test mandatory:

• 🔴 Open a monochrome red background and hold for 30 seconds – if there are traces of icons, the matrix is worn out.
• 🟢 Check the green and blue colors for the cheap ones. AMOLED (For example, in the Redmi Note 11 Pro, there is often “dirty” in the corners.

Don’t forget to test the sensor:

• 🖐️ Swipe your finger around the edges of the screen – if the trigger “jumps”, this is a sign of a malfunction of the digitizer.
• 🎮 Start a multi-touch game (for example, PUBG Mobile) and check if the touches are sticky.

On models with 120 Hz (POCO F4 GT, Black Shark 5) check the smoothness of the scrolling: go to Settings → Display. → Upgrade frequency and turn on 120Hz. If the screen is "slowing down," it could be a graphics chip defect.

3.Camera testing: how to identify soap modules and software artifacts

Xiaomi cameras often suffer from two problems: replacement with cheap counterparts (especially in Redmi after repair) and software restrictions (for example, disabled). 4K@60fps Start by checking the hardware:

Take pictures of all modules (main, wide-angle, macro, telephoto) of the following scenes:

• 🌳 Trees against the sky, check the detail and CDD. On cheap modules, the foliage will be smeared».
• 📄 Text on paper -- zoom in and check for sharpness at the edges. If the letters float, it's a sign of a broken lens.
• 💡 Light source in the dark – on non-original modules will appear purple “lights».

Pay attention to the front camera: in models Xiaomi Civi and Redmi Note 12 Pro+ It often fails after falling, and take a selfie with the beauty on and off -- if you don't have filters, your face looks soapy, your matrix is damaged.

Check the video footage:

• 🎥 Record the video in 4K and 1080p — if 4K The picture “twitches”, this is a sign of overheating of the processor or defect ISP-chip.
• 🔊 Turn on the microphone and record the sound – on many used Xiaomi it “hrizzes” due to the oxidation of contacts.

⚠️ Warning: If a vendor refuses to let the cameras be tested for longer than 2-3 minutes, this is a reason to be wary. 11T Pro after replacement of thermopastes).

For a deep check, use GCam (if supported) – on non-original modules, this camera will either not start or will give an error “No cameras available”.

4.Battery: How to know the real wear and tear and avoid "bloating"

The battery is the most consumable component in a smartphone, and even if the seller claims that the battery is "new," it could have dropped 30 to 40 percent.

• 🔋 Carefully press the back cover in the battery area – if the screen is “playing” or there is resistance, the battery is swollen.
• 📱 See if the screen “walks” when pressing corners – this is a sign of deformation of the body due to a bloated battery.

Now we turn to the diagnostic program:

1. Enter the code ##4636 in the phone application## → Battery information. Check out Battery Health. If you're above 20 percent, you'll have to change the battery soon.
2. Install the AccuBattery app and check for Capacity Rating. For example, if the Redmi Note 11 (original capacity of 5000 mAh) shows 3800 mAh, that's critical wear.
3. Connect the charger and see the charge rate. On models with Fast Charge (for example, the charge rate, POCO X4 Pro) the first 30% should be charged in 15-20 minutes, if longer - a problem with the battery or charging controller.

Pay attention to the temperature:

• 🌡️ If the smartphone is heated above 40°C when charging, this is a sign of battery degradation or controller failure.
• ❄️ If the battery is rapidly depleted in the cold (for example, in the −10°C), its chemical composition is impaired.

💡

If the seller claims that the battery is new, ask for a replacement check. Without the document, there is a risk that a cheap analogue is installed (for example, instead of the original one). ATL Coslight is a Coslight that will last a maximum of a year).

5 Performance and iron: how to detect chip swapping

Many Xiaomi used-to-use products are sold after repairs, where they could replace key components, such as the processor, RAM or storage, which is critical because they are cheap (eMMC instead of the main components). UFS) significantly reduce productivity.

Start by checking the processor model:

1. Install. CPU-Z or AIDA64 And compare it to the official model specifications. For example, the Redmi Note 10 Pro should have a Snapdragon. 732G, Not Snapdragon. 720G (It's a sign of a fee swap).
2. Check out the "Architecture" in AIDA64 — if ARMv8.2 indicated ARMv8.0, This could be a sign of a firmware from another model.

Testing memory and storage:

• 🧠 Run AnTuTu Benchmark and compare the result to the reference values for your model, POCO X3 Pro should be gaining 350,000+ If it's 20 percent less, it's a sign of trottling or chip degradation.
• 💾 V AIDA64 check the type of memory: UFS 2.2 (the norm for modern models) or eMMC 5.1 (cheap replacement), in the second case, the smartphone will “brake” when recording video in the video. 4K.

Be sure to check the trottling (decreased performance due to overheating):

• 🔥 Launch it. 3DMark (Wild Life test and watch out for FPS. If after 5 minutes the frame rate drops by 30%, it is a sign of wear of the thermal paste or damage to the cooling system.
• 🧊 On models with LiquidCool (Black Shark, POCO F4 GT) Check if the liquid is “bubbling” when shaken – this is a sign of leakage.

⚠️ Note: If the AnTuTu section «CPU» It doesn't show all cores (like 4 instead of 8), it's a sign of clusters being disabled because of CPU damage.

Verification IMEI, locking and "gray" firmware

One of the most common scams in the sale of used Xiaomi – substitution IMEI or the presence of locks (for example, from the operator or by loss) This can make the smartphone useless after flashing or resetting.

How to check for IMEI:

1. Type *#06# and it will appear on the screen. IMEI. Compare it to the number under the battery (if the case is removable) or on the box.
2. Check it out. IMEI If the model does not match the stated one (for example, instead of Redmi Note 11 shows Redmi). 9A), it's a fake.

Checking locks:

• 🔒 Put it in. SIM-If you have a card from another operator, try calling if you see a message that says "SIM-network unlock" PIN», smartphone is tied to the operator.
• 🔓 Go to Settings. → The phone. → Status SIM-If the status is "Blocked", the device is blacklisted (stolen or unpaid).

The danger is represented by “gray” firmware (for example, Chinese). MIUI global models):

• 🌐 Go to Settings. → The phone. → Version. MIUI. If there is a name at the end «CN» (for example, V14.0.3.0.TLCCNXM), It's Chinese firmware. It may not support Google Services and may have language restrictions.
• 🔄 Ask the seller to make a reset (Settings) → Additionally. → If the reset appears Chinese or activation error, the firmware is informal.

Critical: if the menu "For developers" (Settings) → The phone. → Version. MIUI, 7 times to tap) Option disabled «OEM Unlock, which means that the smartphone is tied to the account of the previous owner, it will be impossible to unlock it without a password!

7. Sensors, network and additional functions

Many customers forget to check the sensors and network modules, and it is in vain that repairing them can cost half the cost of a smartphone.

Install the Sensor Test (or Phone Tester) app and check:

• 🧲 Magnetic sensor (compass) – if the arrow “jumps”, the sensor is damaged (relevant for navigation).
• 📡 Approximation sensor - cover the top of the screen with your hand during the call. If the screen does not go out, the sensor is defective.
• 💡 Light sensor -- change the brightness in the room. If the automatic adjustment is not working, it's a sign of contact oxidation.
• 👆 Gyroscope and accelerometer - tilt the phone. If the test shows the wrong angles, the sensor is damaged (a common problem after falls).

Verification of network modules:

• 📶 Put two in. SIM-maps and check the work 4G/5G Both of them. 5G (Like Redmi. K50) Both SIMs must catch the fifth net.
• 📞 Call another phone and check the quality of the communication. If the voice "breaks" or you hear interference, it is a sign of a modem malfunction.
• 🌍 Turn it on. GPS And check the accuracy in Google Maps. If the coordinates jump by 50.+ Meters, antenna damaged.

Don’t forget about the additional functions:

• 🎮 IR-port (if any): check the remote control from the air conditioner (Mi Remote app).
• 🔊 Stereo speakers: in Xiaomi 11T Pro and POCO F4 GT There must be a clear balance of sound, and if one speaker is wheezing, it's a sign of moisture.
• 🔋 Wireless charging (if supported): check the charge rate. on Xiaomi 13 it should be at least 30W.

💡

If the fingerprint sensor (in-screen or on the button) works again, it is a sign of wear and tear of the sensor. its replacement costs 3-5 thousand rubles, which is comparable to the cost of a budget Xiaomi.

8 Final Check: What to Do Before Payment

If all tests are passed, there are a few critical steps before transferring money:

1. Ask for the original box and documents, and without them, you can't use the warranty (if it's still valid) or prove that the phone isn't stolen.
2. Make reset to factory settings (Settings) → Additionally. → Recovery and resetting. If the seller refuses, this is an excuse to refuse to buy.
3. Check the link to your Mi Account. After the reset, the phone should not require you to enter your old account. If the message appears "This device is linked to a Mi Account", the device is blocked.
4. Write down the serial number and IMEI You can video with the seller, and that'll help in case of a dispute.
5. Pay only after a full check. No prepayments or "deposits" - scammers often use this scheme.

If you buy through Avito or Yula, use a secure check-in deal. In the case of an offline purchase, meet in a crowded place (for example, in a communication salon) and ask the seller to show your passport.

⚠️ Warning: If the seller is in a hurry or pressing for pity ("we need money urgently"), this is a classic sign of fraud.

After purchase, immediately install Anti-Theft (in Settings). → Google → Security) and link your phone to your Mi Account, which will protect you from theft and allow you to block the device remotely.

💡

Even if the smartphone is externally perfect, without checking IMEI, If you have a lock and battery condition, you risk getting a brick in a month, and if you spend at least an hour on diagnostics, you will save thousands of rubles on repairs.

FAQ: Frequent questions when buying used Xiaomi