How to check Xiaomi when buying from hand: expert guide

Buying a Xiaomi, POCO or Redmi smartphone on the secondary market is always a lottery, where winning in the form of significant savings can lead to loss of money and nerves. The market is oversaturated with restored devices, devices after “drowning” and candid copies that are almost indistinguishable from the original. Competent diagnosis of a gadget before transferring money is the only way to protect yourself from buying an illiquid.

In this article, we will examine not only basic on-set checks, but also in-depth analysis of system logs, display status, battery capacity and component authenticity. Many defects, such as matrix burnout or moisture inside the case, are not visible on a cursory inspection, but are easily detected by special methods.

You should start checking before you meet the seller, analyzing photos and description of the lot, but the tests are crucial live. You will need about 15-20 minutes of free time and, preferably, a connection to Wi-Fi for full verification of the device through the manufacturer's servers.

External inspection and configuration check

First impressions are often deceptive, so the inspection should be done in good light, preferably using an additional light source, such as the flashlight of another phone. Carefully inspect the case for deep chips, cracks and opening marks. screws near the charging port and speakers should not have torn slits or unscrew marks.

Pay special attention to the interface between the screen and the frame. In the original Xiaomi devices, the gaps are minimal and uniform throughout the perimeter. If you feel a step with your finger or see uneven application of glue, this is a sure sign of poor repair or replacement of the display module with a cheap analog.

⚠️ Warning: If you see corrosion (green or white) in the charging port or on the speakers under the magnifier or when the camera is enlarged, you should not buy it, this indicates moisture, which can lead to sudden death of the board in a week or a month.

Check all physical buttons, volume and switch on, they should be clear, elastic without jamming, and check the tray for the snag. SIM-cards: it must be original, match the color of the case and easy to retrieve.The presence of foreign objects in the slot or tight stroke may indicate problems with the motherboard.

Diagnostics of the display and touch screen

The screen is the most expensive and fragile element of a smartphone, so it should be checked as much as possible. Turn on the device and set the brightness to maximum. Open a white image (through a browser or a standard gallery) and carefully examine the surface. A quality AMOLED or IPS matrix should not have pink spots, yellowness at the edges or vertical stripes.

To check the touchscreen, you don't need to download third-party apps. Built-in engineering allows you to make an accurate diagnosis. Open the phone book and type ##6484##. If the menu doesn't open, try ##4636## or go to Settings → About Phone → MIUI version (you need to quickly press 7-10 times on the logo).

In the CIT (Customer Inspection Test) menu, select "Touchpanel" or "Display" and you will be asked to swipe your finger across all the grid cells, which is a critical step: draw a line through each square, making sure there are no dead zones left. Often, the touchscreen does not work in the corners or in the center, making it impossible to use the phone.

Also check for flickering (PWM) at low brightness. Point the camera of another phone over the screen of the device being checked. If you see strong black stripes running across the screen, it can be eye-tiring, although for many Xiaomi models this is the standard behavior of the matrix.

Authentication and IMEI

The market is flooded with copies of Redmi budget models and POCO, They're 95 percent copying the original, but they're weak in hardware. IMEI-Find the sticker on the box (if any) and compare the numbers to the ones displayed on the screen when you type *#06#.

In addition to visual matching, you need to check the status of the device on the official Mi Verify website. IMEI-The system must show the exact device model, color and activation date, and if the site says "Not found" or the model is different, you'll see a replica or a Frankenstein).

It is important to understand the difference between the Global version and the Chinese version with installed firmware. Chinese versions (CN) are often cheaper, but they may lack some LTE frequencies (for example, Band 20), which will worsen network catching in rural areas. In the Settings menu → You can see the bootloader unlock status on the phone. If the status is "Unlocked", the device could be reflashed to bypass regional restrictions.

Testing of cameras and multimedia

Cameras are one of the main things that users are looking for: Run a standard camera app and take a few pictures in good light and in low light conditions. Pay attention to the focus speed: the original module focuses instantly, whereas in cheap replacements or replicas this process can take seconds.

Be sure to check all lenses if there are more than one. Switch to a wide-angle lens and a TV (zoom). If the camera app flies out when switching, a black screen appears, or an error "I failed to connect to the camera", this indicates problems with the plumes or oxidation of the module contacts.

The sound system also requires testing. Play a YouTube video or music track at maximum volume. The speaker must not wheez, rattle or make extraneous sounds. The speaker is checked by a test call: the voice of the interlocutor must be clear, without the effect of "underwater".

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Take a photo of a white sheet of paper. If you see black dots or blurred spots in the picture, it means that the camera matrix or the protective glass of the lens is dust or dirt, which will require cleaning or replacing the module.

Diagnostics of battery and charging system

Battery status is a critical parameter when buying a used smartphone. Unlike the iPhone, Android doesn't have a built-in cycle counter on the menu, but you can "ask" the battery status. In the CIT engineering menu, select "Battery" or "Charging" to show current status, voltage and, sometimes, health status (Good/Bad).

A more accurate method is to use the AccuBattery utility or analogues, but for a quick check, just look at the discharge rate. If the charge drops by 10-15% in 10 minutes during active use (camera, browser), the battery is worn out, and the phone should not heat up in the area of the camera or the bottom of the case during normal charging.

Check the USB-C port. Insert the cable at different angles: charging should not be lost at the slightest movement. If contact is lost, you may need to replace the charging connector, which is a common and inexpensive, but unpleasant procedure.

⚠️ Note: If the phone charges only when it is turned off or spontaneously reboots when the charger is connected, this is a sign of a deep discharge of the power controller or damage to the board.

Visually inspect the back cover (if it is glass) for bloating. Put the phone on a flat surface and try to spin it. If the device spins like a yule due to a convex battery, it is fire-prone and requires immediate replacement.

Checking communications, sensors and biometrics

Functionality of communication modules is checked by the installation SIM-Make sure the phone sees the network. 4G/LTE, It's running the Internet through mobile data and it's going through incoming/outgoing calls. Check Wi-Fi: the device needs to see and connect to the networks without constant interruptions.

Sensors are a hidden part of the smartphone that often fails after falls. In the same CIT engineering menu, there are tests for each sensor:

• 📱 Proximity Sensor: Close the top of the screen with your hand, the screen should go out.
• 🧭 Gyroscope/Accelerometer: spin the phone, the image on the screen should respond to tilts.
• 🔦 Flashlight: The flash should light up and burn smoothly, without blinking.
• 📡 GPS: Run the maps and check if the location is determined.

Separately, check the fingerprint scanner and face unlock. In the security settings, delete the old prints and add a new one. The scanner must read the finger the first or second time. If the system writes "failed to recognize" often, the scanner plume or the module itself may have been damaged.

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The operation of all sensors in engineering mode is the main indicator that the phone was not seriously damaged in a fall or flood, as these elements fail first.

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