Although the Samsung Galaxy S21 is a potent smartphone, many users could experience "no signal" issues. A loose antenna connector or a broken flex cable on the motherboard are the most common causes of this problem, while there are other possible causes as well. Fortunately, you can use the following methods to fix it yourself. Phonefix will give you comprehensive disassembly and repair instructions so you can get your Samsung Galaxy S21's no signal issue fixed as soon as possible.
I. Common No Signal Problems and Causes
The "no signal" problem usually affects the phone's communication functions, preventing users from making or receiving calls or using data networks.
Common causes include:
· Loose or damaged antenna cable;
· Broken flex cable on the motherboard;
· Faulty antenna connector near the daughterboard;
If your phone is experiencing a similar problem, the following repair steps will help you resolve it.
Required Tools:
· Hot air gun or hair dryer;
· Suction cup;
· Plastic pry bar (pry tool);
· Phillips 00 screwdriver;
· Replacement adhesive (back cover);
· Soldering station;
II. Repair Steps
Step 1: Power Off and Prepare for Disassembly
Before starting any repair work, power off your device and remove the SIM card tray. Ensure the device is completely powered off to avoid short circuits or other safety issues.
Step 2: Remove the Back Cover Glass
Removing the back cover of the Samsung Galaxy S21 is the first step in the repair. Since the back cover is held in place with strong adhesive, handle it carefully during removal.
1. Use a hot air gun or hair dryer to heat the edges of the back cover. Heat for about 2-3 minutes to soften the adhesive, making the back cover easier to remove. Do not concentrate the heat in one spot to avoid damaging the glass.
2. Use a suction cup to hold the back cover in place, then carefully pry it open with a plastic pry bar. The pry bar can help you avoid scratching other parts of the phone.
3. Gently separate the back cover, prying it along the edges until it is completely separated.
Step 3: Disassemble Internal Components
After removing the back cover, you need to continue disassembling the internal components to further check for signal problems.
1. Remove the wireless charging coil: Use a Phillips 00 screwdriver to unscrew the screws securing the wireless charging coil.
2. Remove the speaker assembly: Continue disassembling the speaker assembly, using a screwdriver to remove the screws securing the speaker.
3. Disconnect the battery: For safety, you need to disconnect the battery flex cable next. Carefully disconnect the battery flex cable using a plastic pry bar to avoid any current transmission.
Step 4: Check Signal Cables and Cables
"No signal" problems are often related to the phone's antenna cable or flexible cable. In this step, you need to check that these cable connections are secure.
1. Check the antenna cable connection: The antenna cable usually extends from the motherboard at the top of the phone to the daughterboard at the bottom. Check if the cable connector is loose or damaged.
2. Check the coaxial cable: Confirm that the coaxial cable is securely connected. Loose cables are a common cause of signal problems.
Step 5: Repair or Replace Damaged Cables and Connectors
If you find damaged cables or connectors, you will need to repair or replace them.
1. Micro-soldering Repair: If the connector is damaged, you may need to perform micro-soldering repair using a soldering station. Use appropriate soldering tools and materials to ensure a strong solder joint.
2. Replace Flexible Cable: If the flexible cable is broken or damaged, you will need to replace it with a new one. Remove the old cable and install the new flexible cable, ensuring a secure connection.
Step 6: Reassemble the Phone
After completing the repairs, you can begin reassembling your Galaxy S21.
1. Reconnect the Battery Cable: Ensure the battery cable is correctly connected to the motherboard and check that the connection is secure.
2. Install the Internal Shielding: If the shielding was removed, reinstall it inside the phone and secure it with screws.
3. Apply Replacement Adhesive: Apply new adhesive between the back cover and the phone frame. Ensure the adhesive evenly covers the entire contact surface to ensure a strong bond between the back cover and the phone frame.
4. Reinstall the back cover: Align the back cover with the phone frame and press gently to ensure a complete fit. If necessary, use a heat gun to reheat the edges to help the glue hold in place.
Step 7: Power On and Test
After reassembly, power on the phone, insert the SIM card, and perform a full test. Ensure the signal is back to normal, and try making calls, sending text messages, and connecting to a data network to ensure the phone functions properly.
III. Troubleshooting Before Disassembly
Before undertaking complex disassembly, you can try some simple troubleshooting steps to rule out software or settings issues.
1. Check SIM Card and Software Settings
· Toggle Airplane Mode: Go to Settings, enable Airplane Mode, and then disable it again. This can sometimes resolve temporary signal problems.
· Restart the Device: Not restarting the phone for an extended period can also cause signal problems. Try restarting your Galaxy S21 to see if the signal is restored.
· Update Software: Check for system updates. Sometimes software updates can fix signal-related bugs.
2. Reset Network Settings
Go to Settings > General Management > Reset > Reset Network Settings to reset your phone's network settings. After resetting, your phone will restore its default network configuration, which can sometimes resolve signal issues.
3. Force Restart
If the above methods don't work, you can try a force restart. Press and hold the power button and volume up button simultaneously until the Samsung logo appears on the screen; the phone will automatically restart.
These comprehensive instructions will help you fix your Samsung Galaxy S21's no-signal issue on your own. Although some disassembly skills are needed for this process, you may address the issue as long as you properly follow the stages. Use the appropriate equipment and supplies, be patient, and pay close attention to detail while making repairs. We strongly advise buying high-quality repair tools and parts from China Phonefix if you require them. A variety of expert mobile phone repair tools are available from China Phonefix to assist you in performing delicate disassembly and repair tasks. You will be more confident in your repairs after investing in expert equipment, which will guarantee more reliable and long-lasting repair outcomes.
