Modern smartphones, including the popular Xiaomi Redmi 9, require precise handling when installing communication modules. Installation can cause the device to simply not see the operator’s network or, worse, damage contacts. Many users have difficulty first getting acquainted with the combined tray that serves both memory cards and SIM cards.
In this article, we will take a closer look at the installation process so you can quickly start using mobile internet and calls. We will look not only at the mechanical part of the process, but also at software settings that often require attention after the physical installation of the chip. It is important to understand that the Redmi 9 has its own design features that distinguish it from the older or, conversely, flagship models of the brand.
Before you start, make sure you have all the tools you need on hand. Usually, a special paper clip is bundled with your phone, but if it's lost, a thin needle will do. Carefulness is the main key to success, since the tray mechanism is quite fragile and does not tolerate rough physical stress.
Tool preparation and map format verification
The first step is always to prepare the workspace and check compatibility. You will need the right size SIM card itself. Today, the de facto standard is the nano-SIM format, which is supported by the Xiaomi Redmi 9. If your card is old, it will have to be replaced in the operator's cabin or carefully trimmed according to the template, although the latter option carries the risk of damage to the chip.
You also need to make sure that the phone is turned off. While many modern devices support hot replacement, to correctly identify the network and avoid short circuits, it is better to completely shut down the system, which is especially true if you are changing the operator or using a new SIM for the first time.
Pay attention to the status of the tray and contacts. They should be free of dust, oxides or moisture. Any foreign particles can disrupt electrical contact, and the phone will constantly lose the network or show an error "No SIM card."
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Always wipe the SIM card contacts with dry soft cloth before installation to ensure a stable connection to the motherboard.
Search for tray and extraction of mechanism
Finding a SIM card slot on the Xiaomi Redmi 9 is easy, but it is important not to confuse it with a noise reduction microphone. The tray is located on the lower end of the device, to the right of the USB Type-C connector. It is a narrow oblong frame, recessed into the body.
To extract the tray, take a paper clip from the kit or a thin needle. Put it into the hole perpendicular to the plane of the body. Don't press too hard -- a fairly confident but moderate press. You should feel a slight click of the spring, after which the tray will extend slightly outwards.
⚠️ Warning: Never use thick objects such as toothpicks or pins, as they can get stuck inside the hole or damage the push mechanism, which will require disassembling the phone.
Once the mechanism has moved, gently pull it with your fingers. Don't pull sharply so as not to damage the internal plumes if the tray is stuck. Make sure you remove the tray, rather than just open the plug (although there is no plug per se, only a retractable element in this model).
Orientation and installation of the SIM card in the tray
The most important thing is to put the chip in the pad. Xiaomi Redmi 9 tray combined: one side is designed for a microSD card, and the other has two places for SIM cards. It is important not to confuse the sides and orientation, because inserting the card “wrong” physically possible, but it will not work.
Look at the shape of the cutout in the corner of the SIM card. It has a cut angle that should match the shape of the notch in the tray. Golden contacts should always look down to the phone screen (or up if you look at the card inserted in the tray, but with contacts to the device board). Redmi 9 tray usually has a schematic image that tells you how to put the card.
- 📱 Take the SIM card by the edges, trying not to touch the golden contacts with your fingers, so as not to leave a fat plaque.
- 🔍 Combine the cut corner of the card with the corresponding ledge in the tray compartment.
- 👇 Make sure that the card lies exactly in the same plane with the edges of the tray and does not protrude beyond it.
If you use two SIMs, the second one is installed in the adjacent compartment in a similar way. Note that the memory card slot is often located on the back of the tray or requires a choice between a second SIM or a flash drive. Redmi 9 has a hybrid slot, so carefully study the shape of the cells.
☑️ Pre-installing check
Installation of the tray back into the body
Once the SIM cards have taken their place, you need to return the tray to the phone. This action requires care, because the wrong input angle can break the contacts inside the smartphone.
Put the tray into the slot to the point. You have to feel the spring resistance, and then you have a slight click when the mechanism locks in. The tray should align with the frame of the case and not protrude out. If it sticks out, you have inserted it on the wrong side or skewed it.
| Element | Action. | The result |
|---|---|---|
| Tray | Insert before clicking | Locking in the hull |
| SIM card. | Contact down. | Data reading |
| Paperclip | Pushing the hole | Removal of tray |
| Corps | Clearance check | Leakability (conditional) |
If the tray does not enter easily, stop and check the orientation. Forced indentation can cause mechanical damage to the internal contacts, the repair of which will require the replacement of the connector in the service center.
First Start and Setup of the Network
After a successful physical installation, turn on your smartphone. Press and hold the side power button until the MIUI logo appears on the screen. The system starts loading, and in the process it will poll the communication module. If the SIM card is working, signal level indicators and operator designation will appear at the top of the screen.
In some cases, especially during the first installation or after reset, the phone may request a phone to be sent to the phone. PIN-This is the security code of the SIM card itself, which is often the default of 0000 or 1234, but it's better to check it with the operator or on the plastic card holder that came with it. PUK.
What to do if you've asked PUK-code?
If the network indicators don't show up, check the settings. Go to Settings. → SIM-Make sure that the SIM card activation sliders are on, and you can set up your preferred network type, such as selecting the preferred network type. 4G for maximum internet speed.
Diagnostics of problems with the definition of the SIM card
Sometimes it happens that everything is done correctly, but the phone says, "Sim card not found." This can be due to a software failure or contamination of contacts. Try rebooting the device again. If it does not help, remove the tray and wipe the contacts of the SIM card with a wipe or an alcohol napkin.
It’s also worth checking if your SIM card supports modern communication standards, and very old cards released many years ago may not work properly on the 4G/LTE networks that Xiaomi Redmi 9 is actively using.
- 🔄 Perform a full smartphone reboot to update your online registration.
- 🧹 Clean the SIM card and tray contacts from oxides and dust.
- 📡 Check the SIM card in another phone to rule out the card itself.
⚠️ Note: If the phone sees the SIM card but does not catch the network, check if the flight Reim is enabled. Also make sure that the account has funds and the data service is activated by the operator.
Setup of two SIM cards and the Internet
Xiaomi Redmi 9 supports two SIM cards at the same time, which is very convenient for separating personal and work calls. → SIM-You can assign cards and mobile networks to which card will be used for mobile Internet by default, which is an important parameter, since the Internet can only work through one active SIM.
It also sets preferences for voice calls, so you can choose to always ask, if you want to decide which card to call from before each call, or prioritize your SIM, and the flexibility of MIUI allows you to customize your phone to suit any user's needs.
Be sure to check roaming if you are abroad. To work on the Internet while traveling, you need to enable data transfer and roaming permission in the settings of a particular SIM card. Without this step, the Internet will not work, even if the balance is positive.
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Proper installation of the SIM card is not only a physical coincidence of contacts, but also competent setting of network priorities in the smartphone menu.