Replaced logic board and still having the same no backlight issue.

Replaced the logic board in the display with no difference. Pretty sure I can rule out logic board failure. No backlight but the display still has a picture with flashlight head closely. And the camera, usb, and ethernet still work the same. The charging for the older macs still works as well. Would it be the power supply not applying power to the backlight or the LCD? I have had stints of perfect operation in short bursts regardless of which logic board, but only after lots of messing about with plugging power in and removing it. I really don’t have another resource for information like this.