The screen went black today yet the MacBook still thought the screen w

I have a MacBook Pro 13in (2012) connected to a 27in cinema screen which I have had for eight years. The screen went black today yet the MacBook still thought the screen was connected. My solution was to disconnect the power, coming from the cinema screen to the MacBook and use the original power supply for the MacBook. I think there's a PSU problem on the cinema screen and likely this is a temporary solution.