Buying a used Xiaomi Redmi smartphone or even a new device with your hands is always a risk of running into hidden defects. Even in official stores, there are returns with malfunctions that sellers do not mention. This article will help to identify all possible problems, from battery wear to hidden traces of falls or repairs. We will analyze hardware and software methods of verification, including tests used by service centers.
Redmi's lineup is low-end and highly functional, making it popular in the aftermarket, but that's what creates risks: cheap parts wear out faster, and unscrupulous sellers often hide the fact of replacing the display or battery. Our instructions cover 95% of possible malfunctions – from inspection to inspection IMEI Use it as a checklist before you buy or to assess the status of your device.
1. External inspection: what gives the “broken” smartphone
Start with visual diagnostics -- it takes 5 minutes, but it can detect up to 30 percent of the defects.
- 🔍 Case: microcracks on plastic (especially on the Redmi Note) 10/11), There's chips on the metal frame, there's glue after you disassemble, and you can see the gaps between the body and the screen, and they're talking about falls.
- 📱 Screen: Even if there are no cracks, check for "yellow spots" (maritime burnout) and "broken pixels" (dots that do not change color.
- 🔋 Connectors: Insert charging cable - if it hangs, connector USB-C It is a common problem with Redmi. 9A/9C). Check the tray for SIM-play-card.
- 🎧 Speakers and microphones: Apply your ear to the bottom of your body when playing music – wheezing or sound distortions may indicate moisture.
Pay special attention to the following repairs:
- 🛠️ Plugging off labels (for example, under the slot cover) SIM) — post-mortem.
- 🔧 Scratches on screws under the back cover (seen at the lumen).
- 🔋 Uneven wear of the battery (if the phone has already been disassembled).
⚠️ Warning: If a vendor refuses to remove a cover or protective film, it is a red flag, often with cracked screens or traces of recovery from a fall hidden beneath them.
Screen check: tests for broken pixels and sensor
The display is the most expensive part of the Xiaomi Redmi, and its defects are often masked.
- Broken pixel test: Open an online service or install Screen Test. Turn red, green, blue, black and white, and the broken pixels will be visible as contrast points.
- Sensor check: In the same app, select Touch Test. Swipe your finger around the screen – if there are non-responsive areas, the sensor is damaged (a common problem after changing the glass).
- Yellow Spot Test: Turn on maximum brightness on a white background. Yellow or purple stains indicate matrix degradation (typical for Redmi). 8/9 after 2 years).
For AMOLED-screens (for example, in Redmi) K50) check in:
- 🔄 Burn-in effect: display a gray background – if the interface contours (such as keyboards) appear, the matrix burns out.
- 🌈 Color rendering: compare the shades to another device. A greenish or pink shade of white is a sign of malfunction.
| Screen defect | Reason. | Can we fix it? |
|---|---|---|
| Broken pixels | Physical damage to the matrix | Just a screen replacement. |
| Yellow spots. | Degradation of illumination or glue | Sometimes it helps to warm up (temporary solution) |
| Sensor malfunction | Damage to the plume or controller | Replacement of touch glass or plume |
| Burn-in (burn-in) | Long-term display of static elements | Not fixed, only matrix replacement |
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If the Redmi screen flashes when the brightness changes, the problem may be the firmware. Try resetting to factory settings (Settings) → The phone. → Resetting settings).
3. Battery Diagnosis: How to Find Out Real Wear
Battery is a weak spot for all Xiaomi Redmis, especially after 1-2 years of use. Official capacity data is often overstated, so independent tests are needed.
Methods of verification:
- Using the engineering menu: ##4636### Select Battery Information. Battery health will show wear rate. A value below 80% is critical.
- AccuBattery: Shows real capacity (e.g., 3800 mAh instead of the declared 5,000 mAh) and discharge rate. If the phone runs 1% per minute in idleness, the battery needs to be replaced.
- Heating test: run a resource-intensive application (for example, 3DMark) Check the battery temperature through AIDA64. If it's 45.°C is a sign of degradation.
For Redmi Note models 10/11 And the newest problem is "battery bloating:
- 🔋 The case is curved (especially noticeable on the table - the phone is swaying).
- 📵 The screen "steps away" from the body at the edges.
- ⚡ The phone spontaneously turns off when charged 30-50%.
⚠️ Warning: If the battery is swelling, you can't keep using the phone, you can risk fire).
Check your health through #4636##|Install AccuBattery for capacity test|Start a stress test (heating)|Check the hull for bloating|Checking the time of autonomy (minimum 4 hours in standby mode)-->
Testing of hardware: processor, memory, cameras
Failures in the motherboard or modules often only show up under load. Use these methods to test in depth:
1. Processor stress test:
- Install. CPU Throttling Test (Android) Run the test for 15 minutes. If the CPU frequency drops below 50% of its maximum, there are problems with cooling or power.
- For Redmi with Snapdragon processors (e.g. Redmi Note 12 Pro)+) If the phone is slowing down after 5 minutes of play, you need to change the thermal paste.
Memory and storage check:
- 📱 RAM: In AIDA64 Open the Memory section, if less than 70% of the total volume is available, the module may leak or damage.
- 💾 Drive: run the test in AndroBench. read speed below 200 MB/s for eMMC or 500 MB/s for eMMC UFS wear-and-tear.
Diagnostics of cameras:
- 📸 Take a photo of all modules (main, wide-angle, macro) in good light:
- 🎥 Record the video in 4K (Snap or “stepping” indicates problems with the processor or memory.
How to check the infrared port in Redmi?
5. Network and communication check: Wi-Fi, 4G, Bluetooth
Communication problems are one of the hardest to diagnose, and they can be either bad signals or no network at all.
Mobile network test:
- 📶 Enter the dialer: ##4636## → Phone information View the parameter ASU (Signal level. A value below 10 in a city is a bad indicator.
- 🔄 Switch between 2G/3G/4G In Settings → SIM-maps and mobile networks, if the phone doesn't catch 4G — Possible problems with the modem.
Diagnostics of Wi-Fi and Bluetooth:
- 📶 Connect to 5 GHz (if supported) If the speed is below 100 Mbps 2 meters from the router, the antenna is damaged.
- 🔊 Check Bluetooth with headphones: if the sound is interrupted or there is interference, the problem is in the module (often after falls).
3.Verification IMEI:
- Enter *#06# if two are the same IMEI or 0000 – the phone is blacklisted or after unqualified repairs.
- Check it out. IMEI If the status of "Blacklisted" is a device wanted or blocked.
| Problem. | Possible cause | Decision |
|---|---|---|
| No network. | Modem or antenna damaged | Replacement of the communication module |
| Bad Wi-Fi. | Antenna dumping or controller damage | Antenna soldering or board replacement |
| IMEI dropped | Incorrect firmware or repair | Recovery through QCN-file |
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If Xiaomi Redmi does not catch the network after updating the firmware, try to roll back to the previous version. MIUI. Often the problem is solved by resetting the modem settings (Settings). → Additionally. → Resetting network settings).
6. Software diagnostics: hidden errors and viruses
Even if the hardware is fine, software failures can make the phone unusable.
1. Availability of root rights and custom firmware:
- Install Root Checker. If you have a root, the phone could have been hacked (the risk of spyware).
- Check the version. MIUI In Settings → If you have an informal firmware (e.g. xiaomi.eu), it can disrupt the modules.
Virus scanning:
- 🛡️ Use Malwarebytes or Dr.Web. Pay attention to apps with administrator rights – they can be malicious.
- 📁 Check the folder. /system/app through a file manager (for example, FX Unknown files with the.apk extension are a sign of infection.
Performance test:
- Run an AnTuTu Benchmark. Compare the result to the reference values for your model. A deviation of more than 20% down is cause for concern.
- 🔄 Check the lags in the interface: open Settings → Developer → Processor statistics. If booting CPU over 30% in simple – there are background processes in the system.
⚠️ Note: If Redmi has com.android.engmode or com.qualcomm.atfwd, the phone could be used for fraud (e.g., bypassing). SMS-verification).
7.Authentication and history of the device
To make sure you are not facing a fake or stolen phone, follow these steps:
Verification of the serial number:
- Find it. S/N In Settings → Phone or battery (if removable).
- Check it out on Xiaomi's official website. If the data doesn't match, the device is unoriginal.
History of repairs:
- 🔧 Ask the seller for a check from the service center (if the phone was repaired), the absence of a check with visible signs of disassembly is a reason for suspicion.
- 📄 Check the guarantee status of the IMEI If the warranty expired early, the phone could have been repaired.
The clone test:
- Compare. IMEI If they don't match, you're a fake.
- Look at the packaging: Xiaomi’s original boxes have holographic stickers with a serial number that should match the number on the phone.
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If the seller refuses to provide the original box or documents, the probability that the phone is stolen or recovered is that the phone is not a real one. ~70%.