How to check the Xiaomi phone when buying from hand: expert guide

Buying a smartphone in the secondary market is always a lottery, especially when it comes to popular brands like Xiaomi, Redmi and POCO. On the one hand, you can save up to 40-50% of the initial cost by getting a flagship device of the middle class. On the other hand, there is a high risk of running into a restored instance in the basement, a device after pouring or even a stolen gadget. Statistics of service centers show that one in three used phones requires investment in the first month of use.

To avoid turning a bargain into a financial loss, you need to approach the check systemically. Visual inspection is just the tip of the iceberg. The real problems are often hidden in the software part, the state of the battery, or hidden defects in the display that are not visible when you look at a brightly lit store. In this guide, we will analyze a step-by-step algorithm of actions that will allow you to identify 99% of the hidden defects.

Don't be shy about the seller and spend time diagnosing it carefully. If the owner of the device gets nervous, rushes you, or refuses to provide access to the settings and test menu, this is the first alarm. The honest seller has nothing to hide, and the dealer who knows about the problems of the phone will refuse the deal himself, seeing your competence.

Initial visual inspection and inspection of the body

Diagnostics should be started long before the screen is turned on. Take the device in your hands and carefully examine it in good light, preferably using the flashlight of another phone. Pay special attention to the joints of the case and the frame. In the original Xiaomi devices, the gaps between the display and the body are minimal and uniform throughout the perimeter. If you see uneven glue, protruding sealant or differences in the shade of the frame, it may be that the phone was opened or changed to a cheap analogue.

Pay attention to the screws near the charging port USB-C Or Micro-USB. On new or officially restored devices, the screw slits should be perfect, scratch-free. The torn edges are a sign of unskilled intervention. SIM-maps: it should sit tightly, without backlashes, and its color should match the color of the frame perfectly.

⚠️ Warning: If there are signs of heating, battery bloating or glue detachment on the back cover or in the area of the chamber, it is better to stop the transaction immediately.

Check the ports and connectors. Plug in and out. SIM-The card must be operated several times, the mechanism must be clear, without jamming. Check the charging connector: inside it must not be oxides, greenish plaque or compressed dust, which may indicate contact with moisture. Even if the phone is working, contact oxidation can lead to problems charging or transferring data in a couple of weeks.

Diagnostics of the display and touch screen

The screen is the most expensive and vulnerable element in a smartphone. Even if the glass is whole, it can hide a cracked matrix layer or burnt out pixels. First, turn the device on and set the brightness to maximum. Take a white sheet of paper and attach it to the screen, comparing color reproduction. The original AMOLED and IPS matrix Xiaomi white should be clear, without yellow or pink spots.

Then you have to check the touchscreen, and you have to pinch any app icon, and you can swipe it all over the screen, including the edges, and if you have a dead zone in any area, you have to check the multi-touch, and you can pinch the image in the gallery with three or four fingers at once, and all the contact points must be displayed correctly.

• 🔍 Check for broken pixels: Download the screen checker app or open a (single) image of black, red, green and blue. Carefully look for points that burn in a different color or don't change shade.
• 👆 Sensitivity test: Try to quickly type text in any messenger. Skipping letters or "double" presses indicate problems with the digitizer.
• 💡 Brightness and autobrightness: Go out into a bright light or turn on a flashlight. The light sensor must automatically adjust the brightness of the screen. If the brightness slider does not move or the screen is too dim, the sensor is defective.

Special attention should be paid to the problem of "yellow spot" or burnout, which is characteristic of AMOLED screens, most often it manifests itself in the bottom of the screen or in the status bar zone. To identify this, turn on the white picture and minimize the brightness. If you notice the shadow from the keyboard or icons, then the pixel resource is already exhausted, and over time the stain will only become more noticeable.

IMEI verification, warranty status and region

One of the most important steps is to verify the legality of the device.imei (International Mobile Equipment Identity) is a unique identifier that must match in three places: in the phone settings, on the box (if any) and in the check. Dial *#06# in the call to display the information on the screen. Compare the numbers.

Then go to Xiaomi’s official verification site or use third-party services to check for IMEI. This will let you know if the phone is listed in the stolen database, what its original configuration is and when the warranty expired. If the site says “Invalid IMEI” or the model data does not match (for example, instead of the Global version shows China), you may have a re-energized or cloned device.

Also check the bootloader unlock status. If the bootloader is unlocked (open lock icon appears when turned on), this means that the phone was opened software. This voids the warranty and increases the risk of installing malware. To check, go to Settings → About Phone → MIUI version and press 7 times, then in the advanced settings, find the bootloader status.

Testing hardware stuffing through the engineering menu

The MIUI shell (and its successors like HyperOS) has a powerful engineering menu that allows you to test all modules without installing third-party software. To enter, type ##6484##. If the code doesn't work, you may have a modified firmware installed, and then you will have to download applications like Phone Info or TestM.

In the engineering menu, go through all the items. Start with Version, you can see the actual model of the device. Then check Touchpanel (line drawing), Receiver (dynamic sound), Speaker (loud link). Pay special attention to the vibration test: it should be clear, without rattling, which often indicates a disconnected battery or motor backlash.

Sensor testing is a critical step. In the Sensor or Proximity menu, check the proximity sensor. Hold your palm to the top of the screen, it should go out, put it away, it should catch fire. If the sensor sticks, you can't talk normally on the phone, because the screen will be constantly turned off with your cheek. Also check the accelerometer (turn of the screen) and the compass.

• 📡 Communication and GPS: In the test. SIM-Make sure the phone sees the network. 4G/LTE. For GPS It is better to go outside and launch maps - satellites should decide on the future of the satellite. 10-15 seconds.
• 🔋 Battery: The engineering menu often shows the recharge cycle. If the phone is a year and the cycles are 500.+, The battery was changed or operated in the tail and mane.
• 📷 Camera: Check autofocus. Point the camera at close and far. If the focus is walking or crackling, the camera module is faulty.

Assessment of battery and power system condition

Battery is a consumable, and its condition directly affects the comfort of use. Unlike the iPhone, Android doesn't have a built-in battery health meter as a percentage, but there are indirect signs. Go to Settings → Battery and look at the statistics of screen time. If the seller says that the phone holds two days, and the statistics show 3 hours of screen at 20% charge, it's false.

Pay attention to the charging speed. Connect an original (or quality) charger with Quick Charge or PD support. Quick Charge animations (e.g. the MI Turbo Charge logo) should appear on the screen. If the phone charges slowly ("Normal Charging") even with a powerful power supply, the power controller or the cable inside the phone may be worn out.

⚠️ Note: If during the check the phone suddenly turned off when 15-20% charge or after activation shows a charge jump from 5% before 40%, The battery has a "memory effect" or malfunction, and this device will require replacement of the battery immediately after purchase.

For more accurate diagnosis, you can use ADB commands (a computer is required), but for quick suffice check (it is enough) install an application like AccuBattery. Even in 10 minutes of use, it will show an approximate real battery capacity in mAh. If the passport capacity is 4500 mAh, and the application shows 3000 mAh, the battery life is exhausted.

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Heat check: During camera testing (recording 4K video) or running heavy games, touch the top of the case. Local overheating at one point may indicate a fault in the processor or cooling system, rather than just intense work.

Checking cameras, speakers and microphones

The cameras in modern Xiaomi and Redmi are a complex optical module. When checking, take a few pictures in good light and in bad (dusk). The photo should not have black spots (dust on the matrix), rainbow glare or the soap effect on the edges. Turn on the video in 4K and walk around - if the picture is twitched or cracked, the optical stabilization module (OIS) is most likely broken.

The sound part is often ignored. Turn on the tape recorder and record yourself in silence, then in a noisy place. Play the recording. If you hear a crack, hiss or underwater sound, the microphone is faulty. Check the main speaker by turning on the music at maximum volume - there should be no wheezing. Separately check the speaker by calling a friend or by voicemail.

Don't forget the vibrator. Xiaomi often uses good motors, but after falls they can start to rattle, the vibration should be short and elastic (knock) and not long and humming (zhzh).

Final Test: Reset and Test in "Pure" State

The most reliable way to check the phone is to see how it behaves after it's reset to factory settings. Many software bugs, viruses, or hidden account locks come up after Factory Reset. Warn the seller that you're going to do a reset. If he's against it, that's a reason to think.

You can reset via the menu: Settings → Phone → Reset. Once rebooted, the phone should not ask for a password from someone else’s Mi Account (FRP Lock). If the device asks for an email and password of the previous owner, and the seller “forgot” them, you have a stolen or locked device.

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Buying used Xiaomi is justified only if after resetting the phone does not require an account of the previous owner and works stably for 15-20 minutes of "clean" use.

After reset, check Wi-Fi and Bluetooth. Connect to the network, try to download a file. Bluetooth should see devices around and mate with them. If the Wi-Fi module is unstable (the network often falls off), this can be a sign of a chip failure on the board, which is a fatal malfunction.

Frequently Asked Questions (FAQ)