The power unit is obviously what powers your device. Without this you cannot use the device at all whatsoever.
Use this guide to uninstall the power unit from your device, then follow it in reverse order to install the new part.
On the bottom of the device, you'll see 4 rubber pieces at the corners. Peel off these rubber pieces.
Unscrew the 4 10mm Philips J1 screws beneath them.
Poke through said stickers and unscrew the 2 10mm Philips J1 screws beneath those.
Insert the blue plastic tool into the corner of the bottom faceplate and slide along the edge.
Remove the power supply. Be careful as the power supply is still connected to board.
Unplug the power supply from the small motherboard as shown.
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