The screen turns off
I have a mid-2009 iMac 27 ". The problem is that the screen is turned off. what I have currently connected to an external monitor, which has no problems, I discard it video chip problem.
When I climb the brightness, it turns off. The iMac continues to work, because I work with external monitor.
What would be the problem and how I fix it?
iMac 27 inch late 2009 core i5. 12 GB ram DDR3, Video ATI Raden HD 4850 512MB
iMac + monitor: http://subefotos.com/ver/?a7964f9b1ab3c8...