Xiaomi’s mobile devices have long proven to be reliable assistants, but the initial setup process sometimes causes difficulties for new users. The question of how to properly install the communication module is one of the most common when first familiar with a smartphone. Installation of the chip can lead to a lack of signal or even damage to contacts.
In this article, we will discuss in detail the design of the Redmi 9 tray, as it has its own characteristics compared to previous generations, you will learn how to place contacts, how not to confuse slots and what to do if the phone does not see the network after installation.
We will also look at the nuances of working with a hybrid slot that allows you to choose between a second SIM card or a memory expansion card. This is a critical point for those who plan to use a large amount of media.
Preparation of the workplace and tools
Before you start manipulating the body of the device, you need to ensure a clean and well-lit space, dust and small debris trapped inside the case can disrupt the contact of metal sites, it is recommended to wipe the surface of the table with dry cloth and wash your hands to avoid leaving greasy marks on the contacts.
To extract the tray, you'll need a special key-clip that comes with the device. If the original tool is lost, it can be replaced with a thin paper clip, straightening one of the ends, or a thin needle. Don't use thick objects like toothpicks or pins, as they can break inside the hole or damage the mechanism.
- 📱 Xiaomi Redmi 9 smartphone with the screen off.
- 🔑 Key to extract the tray (clip or needle).
- 💳 Nano-SIM SIM card (smallest size).
- 🧹 Dry soft fabric for wiping contacts.
⚠️ Warning: Before the procedure is initiated, it is strongly recommended to turn off the smartphone completely. Although modern devices support hot replacement, the power cut will minimize the risk of short circuit or software errors in determining new equipment.
Make sure your SIM card is in the correct format. Modern smartphones, including Redmi 9, use the Nano-SIM standard. If your larger card is larger, you need to carefully cut it out along the contour or contact the operator's salon to replace it with a new one.
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If you use an old SIM card, wipe its contacts with a soft eraser before installing it – this often helps to restore contact if the card has been lying idle for a long time.
Tray design and slot location
The tray in the Redmi 9 is located on the lower end of the case, to the left of the USB Type-C charging port. This is the standard location for most Redmi line devices.The tray design is triple, but has an important limitation: the third slot is hybrid. This means you can use either a second SIM card or a MicroSD memory card, but not simultaneously.
If you look closely at the tray, you can see that it's asymmetrical, one side is bent, which is the shape of the chip, and the plastic holder itself often has a micro-circuit on it that shows exactly how the card should be lying, and the orientation of the contacts is always down to the motherboard when the tray is inserted into the phone.
| Slot | Type of card | Features | 4G support |
|---|---|---|---|
| Slot 1 | Nano-SIM | The main slot | Yes. |
| Slot 2 | Nano-SIM | Additional | Yes. |
| Slot 3 (Hybrid) | MicroSD / Nano-SIM | Choosing one of the two | Depends on the card. |
It's important to understand the difference between slots. The first two are for carriers only, while the third is for general purpose. If you're planning to expand your device's memory, you'll have to sacrifice the option of using a second SIM card, and decide in advance which is more important to you: two numbers or a large amount of storage.
Step-by-step instructions for installing a SIM card
The installation process is simple enough, but requires care. Take the key to extract and find a small hole next to the tray on the lower end. Place the key perpendicular to the body and press with moderate force until a characteristic click. The tray should extend a few millimeters, after which it can be removed with your fingers.
Place the tray on a flat surface and place a SIM card on it. Make sure the notch on the card matches the notch on the plastic. Contacts should look down. Carefully squeeze the card into the recess so that it locks in. If you use the memory card, it is installed over the contacts of the second SIM card into a hybrid slot.
☑️ Installation control
Put the tray back in the case. Make sure you don't mix up the sides: the tray only enters in one position. Don't put too much effort; if the tray doesn't enter easily, flip it over. After installation, turn on the device and wait for the network signal to appear.
⚠️ Warning: Never force the tray into the tray. If it doesn't enter smoothly, it's upside down or inserted by the wrong side.
Once the smartphone is turned on, the system automatically detects a new card; a PIN request may appear on the screen if it was previously installed; enter the operator-provided code or a standard code (often 0000 or 1234) if the card is new; successful registration on the network will be marked by the appearance of operator icons in the status bar.
Setup of two SIM cards and network management
Redmi 9 supports two SIM cards simultaneously on the network 4G. After installing both modules, you need to properly configure their priorities in the system. MIUI. To do this, go to the settings menu and select the item SIM-Maps and mobile networks. Here you'll see both maps installed.
The system will suggest assigning one card to the mobile Internet and the other to the default voice calls, and you can change these settings at any time, and you can also split the cards by color or name (e.g., "Work" and "Personal"), which makes it easier to visually perceive information on the screen.
- 🌐 Mobile Internet: Choose the card with the best data rate.
- 📞 Voice calls: specify the main card or leave a choice at each call.
- 💬 SMS-Messages: Assign a number to send messages by default.
An important parameter is to set up the preferred network type. In the Preferred network type menu, it is recommended to choose Preferably 4G. This will ensure maximum data transfer speed where the carrier coverage allows. If there is no 4G in your region, the phone will automatically switch to 3G or 2G.
The Secret to Switching the Internet
Using a MicroSD card instead of a second SIM
If you don't have enough internal storage of 32 or 64 GB, it makes sense to use an expansion card. As mentioned earlier, the slot for the second SIM card is hybrid. To install the microSD card, you need to remove the tray and insert the card into the third compartment on top of the contacts of the second SIM card (or into a separate compartment if the tray design allows a layered installation, which is typical for the Redmi 9).
Once you have the card installed, the system will suggest that you format it, you can use it as a portable storage device or as part of internal memory, in the first case, the files will only be available after you have the card extracted, in the second case, they will be encrypted and linked to a particular device, and the formatting will delete all the data from the card, so back up in advance.
To check the card, go to the Explorer or Files app, which should show an additional partition of memory. If you use the card to store photos and videos, set the camera to save materials there so that the system partition does not overflow.
⚠️ Note: Use memory cards only from trusted manufacturers (Samsung, SanDisk, Kingston). Cheap cards of unknown brands may have real capacity much less than claimed, which will lead to data loss and system slowdown.
Solution: the phone does not see the SIM card
Sometimes, once installed, users are confronted with a message saying, "No SIM card" or "Only emergency calls." The first step should always be to reboot the device, which allows the system to re-interview the ports and start the communication module. If the reboot didn't work, check if the tray is inserted correctly.
Try to remove the card, wipe the contacts with soft cloth and insert again. Make sure the card is not damaged and has no chips. It is also worth checking the card on the other phone to rule out the chip itself. If the card is working on another device, the problem may be in the settings of Redmi 9.
In rare cases, you need to reset your network settings. Go to Settings → Connection and Sharing → Reset Wi-Fi, mobile network and Bluetooth. This action will not delete your personal files, but will return your network settings to factory values.
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If the phone does not see the SIM card in any slot, but other cards work - perhaps the reader or plume is damaged, which requires contacting the service center.
If the problem is software-related, a firmware update can help. Check for updates in the About Phone section. Newer versions often contain patches for modems of various carriers, which improves compatibility.