The used electronics market is booming, and Xiaomi smartphones are leading the way here thanks to their excellent price-performance ratio. However, buying a device from hand is always a lottery, where there is a high risk of encountering refurbished devices or candid copies after serious repairs. A competent check of the used phone of Xiaomi can save you from financial losses and headaches in the future.
In this article, we will go through all the stages of diagnostics, from external inspection to deep analysis of software through the engineering menu, you will learn to identify hidden defects in the display, check the real capacity of the battery and determine whether the gadget is not listed on the blacklist of telecom operators, this knowledge will become your main tool when bargaining with the seller.
Visual inspection and inspection of the hull assembly
The first thing that catches your eye when you meet a seller is the appearance of the device. Even if the phone is in a protective case, you need to remove it and carefully examine it from all sides in good lighting. Xiaomi body should not have deep chips, cracks or marks of severe impacts that could violate the tightness or internal structure of the board.
Pay special attention to the gaps between the frame and the display, and the quality of the adhesives of the back cover. If you notice that somewhere the body is moving away or the glue is visible, this is a sure sign of unqualified opening. Factory assembly is always characterized by perfect symmetry and no protruding elements.
⚠️ Warning: If you see traces of sealant or glue around the tray SIM-The cards or ports, which means the phone was opened, most likely the battery or the screen was changed, and the leakage was broken.
Check the screws at the bottom charger, they should not be scratched by the screwdriver, the presence of such traces indicates that the device was disassembled, which automatically reduces its market value, and also examine the camera lenses for dust inside the glass, which is a sign of depressurization.
- 🔍 Examine the end of the device for scuffling, indicating wearing without a cover.
- 🔍 Check the tray. SIM-maps: it should be original, smooth and sit tightly in the nest.
- 🔍 Evaluate the state of the volume and inclusion buttons: the move should be clear, without jamming and backlashes.
Diagnostics of the display and touch layer
The screen is the most expensive and fragile element of a smartphone, so it needs to be checked as long as possible. Even if the matrix looks intact, it may have subtle defects that will show up later. Start by turning on the white background (you can open a blank page in your browser) and carefully examine the surface for yellow spots, broken pixels or uneven backlighting.
Next, you need to test the touch layer. You don't have to download third-party apps, you just need to use the built-in engineering menu. Enter the code ##6484## in the Phone app. If the code doesn't work, check in Settings → About Phone → MIUI version if the Advanced Settings option is activated.
In the CIT (Calibration and Test) menu, select "Touchpanel" or "Sensor." Swipe your finger across the screen as you draw lines. They should be continuous, without breaks or spontaneous jumps. Pay special attention to the edges of the screen, where there are often problems with responsiveness after poor glass replacement.
What is a screen burnout and how to find it?
Also check the proximity and light sensor in the same engineering menu. Put your hand to the top of the phone during the tests, the readings should change. A faulty proximity sensor will cause the screen to not go out during the conversation, which is extremely annoying.
Checking the technical condition through the engineering menu
The MIUI Menu is a powerful rapid diagnostic tool that is available to every user, and in addition to the touchscreen test, you can check all the major modules: vibrations, speakers, microphones, cameras and wireless interfaces. Go through each item on the list to see if the components are working.
Of particular interest is the section that shows build and status information, which shows if key components have changed, for example, if a phone is sold as new or in perfect condition, but tests show replacements, it's a reason to make a serious bargain or to refuse to buy.
☑️ Checklist of checks in CIT menu
Don't forget to check the fingerprint scanner. In the test menu or in the usual security settings, add your fingerprint and try unlocking your phone several times. The scanner should respond quickly and without errors. If the finger is read from the fifth time or does not respond at all, the module is faulty or replaced with a poor-quality counterpart.
It's also important to test the communication modules. SIM-map and check if the phone catches the network, whether the mobile Internet is working (4G/LTE) And if it's transmitting sound when you call, antenna problems are a common disease of phones after falls, and they can only be detected in real-world conditions.
Analysis of battery and charging system
Battery status is a critical parameter when buying a used gadget. Over time, the capacity of lithium-ion batteries decreases, and the phone begins to run out in half a day. The CIT menu often has a "Battery" or "PCBA" item that displays battery status. However, more accurate data can be obtained by analyzing logs or using special utilities.
Pay attention to the charging speed. Connect an original or quality charger with Quick Charge or Power Delivery support. Quick Charge animations should appear on the screen. If the phone charges slowly or the process is interrupted by 80-90%, it may be that the power controller is faulty or the battery has completely degraded.
| Parameter | Norma. | An alarm signal. |
|---|---|---|
| Residual receptacle | More than 85% | Less than 80% |
| Recharge cycles | Up to 300 cycles | More than 500 cycles |
| Tension at rest | 3.7B - 4.2B | Races or below 3.5V |
| Charging temperature | 30°C - 40°C | Above 45°C. |
Visually inspect the charging connector, which should be free of pile, oxides or damage to the central tongue, and a loose connector, when the cable falls out at the slightest movement, will require a replacement of the socket, which is an additional expense.
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Use the AIDA64 or AccuBattery app to get detailed battery health statistics if the built-in tools don’t give the full picture.
Identification of counterfeits and status of Mi Account
One of the scariest scenarios is buying a fake. Modern Xiaomi copies may look one-on-one like the original, but inside they have cheap hardware and stripped-down Android. → About the phone and check the model number with the official website of the manufacturer. IMEI-code on the Xiaomi authentication site.
It's important to make sure that the previous owner's Mi Account is deleted from the device, and if the phone is tied to someone else's account, you can't use it fully, and the seller can block it remotely at any time, and when you first turn on, the phone doesn't have to ask for a password from someone else's Mi Account.
⚠️ Warning: Never buy a phone if the seller claims to have "forgot the password" and promises to unlock it later.This almost always means the device is stolen or found and the owner doesn't want to give it away.
Check the status of the device by IMEI in the databases of operators and service centers, which will help you to find out whether the phone is stolen or has been seriously repaired with a replacement motherboard, and there are special online services that you just need to enter a 15-digit number.
Make sure the phone has original firmware. Global versions (Global) have a full suite of Google languages and services. Chinese (CN) versions with a re-stitched global shell may have issues with notifications, banking apps and Widevine (quality video in streaming).
Final performance and memory check
Before you finalize, run a heavy app or game to check your phone under load. The device should not warm up too much at the top (where the processor is) or spontaneously reboot. Lags in the interface on a new device may indicate memory problems or overheating.
Check the amount of RAM and internal memory. In the settings, specify the real volume declared by the seller. Fraudsters often modify the system files so that the phone shows 128 GB instead of the real 16 GB. When you try to write a large amount of data, such “fakes” begin to cyclically overwrite files or give errors.
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The actual amount of memory can only be accurately recognized by a computer and specialized utilities such as FakeFlashTest or h2testw by writing the test file to the full volume.
Test the camera in good and low light. The photos should not be blurry, and the focus should be fast. Check the recording of the video with sound - the microphone in video shooting is often different from that used in calls.
If all tests are successful, you can proceed to payment, and be sure to ask the seller for a check or at least a receipt indicating the IMEI and the date of purchase, to protect yourself in case of hidden defects in the first days of use.