How to Replace the Mainboard on a Lenovo ThinkPad T490: Step-by-Step Guide
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.
