Modern Xiaomi and Redmi smartphones are equipped with high-quality AMOLED and IPS arrays, but even premium panels can have manufacturing defects. The user may encounter “broken” pixels, uneven backlighting or problems with the touch layer immediately after purchase. Visual inspection in bright light of the store does not always reveal hidden shortcomings that manifest themselves only under certain operating conditions.
Timely screening avoids problems in the future, especially if you buy a device from hand or order it online without the possibility of detailed inspection. There are several proven methods, from built-in engineering tests to specialized applications. Initial inspection is best done in the first 14 days after purchase, while the warranty period for the return of the goods of good quality is in force.
In this article, we will take a closer look at all the screen checks you can do, including the hidden developer menus that are often ignored by ordinary users. You will learn to distinguish between color calibration software snags and physical damage to the matrix. This knowledge will help you make the right decision about returning the device or whether it needs to be repaired.
CIT Engineering Menu: Built-in Diagnostic Tool
The most reliable and deepest way to test Xiaomi’s screen is to use the built-in CIT (Customer Integration Test) menu, which is hidden from the average user, but is accessible through special code or system settings, and it tests all hardware components, including the touch layer, the color gamut and the operation of individual display zones.
To enter the diagnostic menu, you need to open the standard Phone application and dial the combination ##6484##. If the code did not work, perhaps your operator has changed the dial format, then go to Settings → About Phone → Version of the kernel and click on it 5-7 times in a row.
In the test list, you're interested in items related to the display, usually called "LCD," "Touchpanel," or "Color." When you run an LCD test, the screen is filled with solid color. Your task is to look closely at the surface for spots, uneven brightness, or points that differ in color from the main background. This is a critical step, since broken pixels are often only visible in a single-colored image.
⚠️ Attention: In the engineering menu CIT Do not press the Fail button unnecessarily, as this may write an error in the device's log file. If the test is successful, be sure to press Pass to ensure that the system records the serviceability of the component.
Testing the touchscreen in this menu allows you to test the response to a multi-touch screen will suggest that you swipe your finger along certain lines or squares, if the line is interrupted or does not respond to touch in a certain area, this indicates a defect in the digitizer, which will not work correctly in games or when printing text.
Checking for broken and stuck pixels
There are several types of matrix defects, and it's important to understand the difference between them: a broken pixel is a dot that is always black and doesn't change color. A stuck pixel burns in one color (red, green or blue) all the time. A third type is a hot pixel that changes color chaoticly, but most often with a white glow.
To detect such defects, the best way to use full-screen online services or YouTube videos is to consistently flood the screen with pure colors: red, green, blue, white and black. On a black background, you can see hot and stuck pixels, and on a white background, black dots. On colored backgrounds (RGB), you can see the uneven glow of subpixels.
- 🔴 Red background: helps to identify problems with red subpixels and uneven backlighting at the edges.
- 🟢 Green background: the most important for AMOLED screens, as green subpixels have a different structure and often burn out first.
- 🔵 Blue background: allows you to notice the “blue veil” or uneven distribution of the blue spectrum, which is often found in cheap cars. IPS matrix.
- ⚪ White background: the main test for broken (black) pixels and the overall brightness of the backlight throughout the area.
There is a permissible number of defective pixels, regulated by the ISO 13406-2 standard. For high-resolution screens (Full HD and above at a diagonal of 6 inches), the presence of 1-2 bit pixels can be considered the norm by the manufacturer, and warranty repair may be refused. However, many stores accept devices with any number of defects in the early days.
Can broken pixels be recovered?
Diagnosis of touch screen and multi-touch
Touchscreen problems often don't show up immediately. The device can spontaneously open apps, not respond to corners or "glut" when typing. Xiaomi has a built-in test to check sensitivity and positioning accuracy, but third-party utilities are also useful.
One of the easiest ways to check is to use a standard Gallery. Open any photo, select the editing mode "Pruning" and try to swipe your finger across the frame. If the frame is shaking, jumping or not following your finger exactly, then the calibration is down or there is a sensor defect, and you can drag and drop icons on the desktop throughout the screen area, including the available corners.
⚠️ Warning: If the screen only responds to touches through the protective glass or when charging is connected, the problem may not be in the matrix, but in a poor-quality charger that creates interference, or too thick protective glass.
For gamers, it's critical to check the multi-touch, the screen has to handle up to 10 simultaneous touches, the CIT engineering menu has a Touchpanel test, where you can see the click map, and if you press with five fingers, and the system sees only four or the dots float, it's a sign of a hardware malfunction of the touchscreen controller.
☑️ Touchscreen check
Use of third-party applications for the test
If the built-in tools don't seem informative enough, you can use specialized software from Google Play. Apps like Test Your Screen, Dead Pixel Test or Touch Screen Test offer automated screening scenarios, they don't require superuser rights and are safe for the system.
These programs often have a "Stuck Pixel Fixer" feature that tries to programmatically restore stuck pixels by changing colors quickly. Although the effectiveness of the method is controversial, it won't take long. The main advantage of the applications is the ability to create a report on the status of the screen, which can be saved as a screenshot to prove a defect in the service center.
When using third-party software, pay attention to the permissions requested. To test the screen, the application only needs access to the display on top of other windows. If the program requires access to contacts, microphone or geolocation, this is suspicious, and it is better to refrain from using it, so as not to violate data privacy.
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Before running heavy screen tests, close all background applications so that the load on the processor does not affect the smoothness of the color rendering and does not distort the check results.
Visual assessment of matrix quality and viewing angles
Beyond technical flaws, it is important to evaluate the subjective quality of the picture. Xiaomi screens, especially in the budget segment of Redmi, can have different types of matrixes. IPS panels sin with a “black veil” (glare) in bright light and less contrast, while AMOLED can suffer from flickering (PWM) at low brightness.
Check the screen when you unlock. If you see a noticeable change in brightness when you see time digits or notifications, you use an aggressive PWM scheme. For people with sensitive eyes, this can cause rapid fatigue. It is also worth checking the viewing angles: tilt the phone at a 45-degree angle. If the colors are heavily distorted or there is a rainbow effect, the quality of the matrix leaves much to be desired.
Notice the frame around the display, which is minimal and uniform on all sides in quality instances, and if the frame is wider on one side (usually at the bottom) or the plume is visible, it may indicate poor build or use of the restored matrix, which is often the nuance of devices that have been repaired.
| Parameter | Norma. | Sign of defect | Impact on use |
|---|---|---|---|
| Broken pixels | 0 pieces. | Black or colored dot | Constant distraction |
| touchscreen | 10 points | Touch skip | Impossibility of play, printing |
| Brightness | Uniform | Spots, yellowness | Discomfort in reading |
| SHEAM (Blinking) | Not too much. | Low-percent pulse rate | Eye fatigue, headache |
What to do if screen defects are detected
If you have identified serious problems during the inspection, the algorithm of actions depends on the status of the device. For a new smartphone purchased less than 14 days ago, the law applies to return goods of good and improper quality. The presence of even one broken pixel (although this is a gray area) or “glitch” touch screen is the basis for a refund or replacement with a serviceable copy.
If the warranty is still valid, but 14 days have passed, you need to contact an authorized service center Xiaomi. Self-repair or attempt to "heat" the screen with a hairdryer will deprive you of the warranty. Engineers will conduct their diagnosis and, if the defect is confirmed, replace the display module.
For hand-held devices, the situation is more complicated. If the defect was hidden by the seller, you can try to negotiate a refund, but if you checked the phone at the meeting and signed the transfer certificate, it will be almost impossible to prove a manufacturing defect later, so checking before buying is the golden rule.
⚠️ Warning: Never try to replace the screen yourself if you don't have experience.In today's Xiaomi, the display is glued around the perimeter, and a careless opening can damage the battery or plumes, causing the device to fail completely.
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Timely detection of a defect in the screen in the first two weeks allows you to return the full cost of the smartphone, so do not postpone a thorough check for later.