Lenovo ThinkPad T490 Laptop Disassembly and Main Board Replacement

In this video, I demonstrate how to repair Lenovo ThinkPad T490. I replaced a broken mainboard with a fully working motherboard. The process begins by disabling the built-in battery via the BIOS setup, followed by carefully removing the keyboard, back cover, and battery. Next, all internal cables connected to the mainboard are disconnected, including those for the display, Ethernet, and Wi-Fi. After unscrewing and removing the heatsink and fan assembly, the damaged mainboard is replaced with a working one from another T490 unit. The system is then reassembled in reverse order—reconnecting cables, reinstalling components, and reattaching the battery and cover. After powering on the laptop and updating the BIOS clock, I use Lenovo's built-in diagnostics to test hardware functionality, confirming that the repair was successful.

🔧 Step 1: Disable the Built-In Battery
Start by turning on the laptop. As soon as it powers up, press Enter to access the boot menu.
From there, press F1 to enter the UEFI BIOS setup. In the BIOS menu:
Go 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 configuration, the BIOS may have either a graphical or text interface, but the steps remain the same.

🎹 Step 2: Remove the Keyboard
Start by gently prying off the left and right plastic keys near the trackpad. Use a Phillips screwdriver to loosen the two captive screws securing the keyboard. Carefully lift the keyboard using a plastic pry tool or card. Release the plastic clips around the edges. Disconnect the two ribbon cables connecting the keyboard to the motherboard. Take your time—this part is delicate.

🔧 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 carefully release the plastic clips. Remove the back cover.

🔋 Step 4: Remove the Battery
Gently disconnect the battery cable from the motherboard. Remove the four M2 screws securing the battery. Lift the battery out of the chassis

🔌 Step 5: Disconnect All Cables
Now, disconnect all cables attached to the mainboard. Start from the bottom section, then move to the top, where you'll find cables for: Ethernet, Wi-Fi and Bluetooth, display and webcam (be sure to lift the small handles before pulling these out). On the right side of the laptop, remove the metal plate by unscrewing all screws. Then, remove three more screws located: near the Ethernet port, in the center, on the far right
🌀 Step 6: Remove the Fan and Heatsink
There are five screws total: one between the fan and the heatsink. Four around the heatsink. Once unscrewed, lift the fan and heatsink combo carefully.

💡 Note 1: Thermal Paste
There will be thermal paste between the CPU and heatsink. Clean and reapply if available.
💡 Note 2: SSD Screw Damage
You may notice in the video that the SSD screw is missing. That’s due to a broken nut on the mainboard. While this could be fixed by soldering a new one, I’m opting to replace the entire board—which is the purpose of this video.

🔁 Replacing the Mainboard
I’m using a working mainboard from another ThinkPad T490. It features an Intel i5 8th Gen CPU with integrated RAM. To install it:
Position the board into the chassis
Secure it with screws
Reconnect all cables
Insert the fan and heatsink, apply thermal paste if available, secure it with the screws
Reattach the SSD
Re-attach the keyboard
Secure the battery and back cover

⚙️ Final Step: Testing the Repair
Plug in a USB-C power supply to reactivate the disabled battery. On first boot, you may see an error about the date and time—don’t worry, this is expected since the real-time clock was disconnected.

Press Enter to interrupt startup, then press F10 to run Lenovo's built-in hardware diagnostics.

This tool lets you test hardware independently of the operating system—a standout feature of ThinkPads. I ran a test on the CPU fan first (critical), then a few more diagnostics. Everything passed! The ThinkPad T490 is now fully functional!

📚 Useful Links
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✅ ThinkPad T490 Specs:
https://psref.lenovo.com/syspool/Sys/...
✅ Boost Your Lenovo ThinkPad T490: RAM, SSD Upgrade, and Ubuntu Linux Installation Guide
https://anavi.org/article/283/
✅ How to Replace the Mainboard on a Lenovo ThinkPad T490: Step-by-Step Guide
https://anavi.org/article/313/