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This tutorials will walk you through the steps how to replace a (broken) mainboard in a Lenovo ThinkPad T490. I recently documented the process in a hands-on repair video. From disabling the internal battery to reassembling and testing the system, I?ll cover everything you need to know to successfully complete the repair.
🔧 Step 1: Disable the Built-In Battery
Before doing anything else, it is critical to disable the internal battery to avoid accidental short circuits.
- Power on the laptop.
- As it boots, press Enter to open the Boot Menu.
- Press F1 to enter the UEFI BIOS Setup.
- In the BIOS menu:
- Navigate to Config on the left panel.
- Scroll down and select Disable Built-in Battery.
- Confirm your choice. The laptop will automatically power off.
Note: Depending on your BIOS version, the interface might look slightly different (graphical or text-based), but the steps remain the same.
🎹 Step 2: Remove the Keyboard
With the battery disabled, you can safely remove the keyboard:
- Pry off the left and right plastic covers near the trackpad.
- Loosen the two captive screws using a Phillips screwdriver.
- Carefully lift the keyboard with a plastic pry tool or card.
- Release the plastic clips around the edges.
- Disconnect the two ribbon cables that connect the keyboard to the motherboard.
Tip: Be patient here?keyboard connectors are delicate and easily damaged.
🔧 Step 3: Remove the Back Cover
To access the internal components:
- Unscrew the six captive screws holding the bottom panel.
- Use a plastic card to gently release the clips securing the panel.
- Lift off the back cover.
🔋 Step 4: Remove the Battery
Next, disconnect and remove the battery:
- Gently unplug the battery cable from the motherboard.
- Unscrew the four M2 screws securing the battery.
- Lift the battery out of the chassis.
🔌 Step 5: Disconnect All Cables
With the battery out of the way, disconnect all cables attached to the mainboard:
- Start from the bottom section and move upwards.
- Unplug cables for Ethernet, Wi-Fi, Bluetooth, display, and webcam (remember to lift the small latches before pulling them out).
- Remove the metal plate on the right side by unscrewing all associated screws.
- Unscrew three more screws near the Ethernet port, center area, and far right of the board.
🌀 Step 6: Remove the Fan and Heatsink
Now, it's time to remove the cooling system:
- Unscrew the five screws securing the fan and heatsink:
- One between the fan and the heatsink.
- Four around the heatsink itself.
- Carefully lift the fan and heatsink assembly out of the laptop.
Note 1: There will be thermal paste between the CPU and heatsink. If possible, clean and reapply new thermal paste before reinstallation.
Note 2: In my video, the SSD screw was missing due to a broken nut on the old mainboard?one more reason why replacing the entire board was the best option.
🔁 Replacing the Mainboard
For this repair, I used a working mainboard from another ThinkPad T490 featuring an Intel i5 8th Gen CPU with integrated RAM.
Here's the installation process:
- Carefully position the new board into the chassis.
- Secure it with screws.
- Reconnect all cables.
- Reinstall the fan and heatsink, applying fresh thermal paste if available.
- Reattach the SSD.
- Reconnect the battery.
- Reinstall the keyboard.
- Secure the back cover.
⚙️ Final Step: Testing the Repair
After reassembly, plug in a USB-C power supply to reactivate the internal battery.
On first boot, you might encounter a date and time error ? this is normal since the real-time clock (RTC) was disconnected during the repair.
- Press Enter to interrupt startup.
- Press F10 to launch Lenovo's built-in hardware diagnostics tool.
This tool allows you to test system components independently of the installed operating system?a fantastic feature unique to ThinkPads.
I ran tests on the CPU fan, memory, and other hardware components. Everything passed without issues, confirming the repair was a success!
🎉 Conclusion
Replacing a ThinkPad T490 mainboard is a manageable DIY project with a bit of patience and the right tools. Whether you're fixing a broken board or upgrading a faulty system, following these steps can save you time and money.
If you found this guide helpful, be sure to check out the full repair video for a visual walkthrough! Once you complete the repair you may consider boosting your ThinkPad T490 with a RAM and a SSD upgrade.
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