Hi all! MacBook Air A2337. There are no traces of liquid or obvious damage, the motherboard is visually in perfect condition. The image is displayed on the external screen, but only the backlight works on the internal screen. There is no image, and the camera on the built-in screen does not work. How to exclude during diagnostics that it is the screen that is broken and not the motherboard? What signals should be present on the connector with the screen removed and connected?