What would cause flickering and no blacklight.

I recently purchased a known “non-working” thunderbolt display.

When plugged in, the computer recognizes the display and is able to use speakers, camera, and USB ports of display.

When display is connected the backlight appears to be not powering on. On some occasions it flickers or may show output properly for a brief period. However, the backlight will then turn off. The video signal or power doesn’t drop off nor disconnects from the MacBook Pro.

Can I narrow this down to a logic board issue or power board issue. I have reseated connectors on the board multiple times with no luck and also tried another thunderbolt cable to the display.

I should mention that a picture is still visible when holding a bright light up to the display. and responds with mouse movement and other inputs. Not a frozen picture.

@danj I replaced the Logic board and am having the same issue… Would it more likely be the power-supply? or LCD itself?