Remove the PCB and put it in a place where it is grounded. Here it is out of the way leaning on the computer.

Note the nine PCB screws on the lid; bottom right.

You will discover dirt and grim on the tray under the PCB. This may not directly cause the PCB to become warm, but it can build up enough to impede the flow of air and reduce the effectiveness of the fans. This should be cleaned.