Why Does a Mac Computer Screen Blink?by Andy Merrett
There may be many reasons why a Mac's display is blinking. From hardware glitsches to software malfunctions or simple connection issues, a blinking screen indicates some type of problem to be addressed.
There may be display problems with Mac laptops, such as MacBook and MacBook Pro, if any part of the hinge, casing or screen has been knocked or damaged. Hardware problems may include intermittent flickering from the screen's backlight, damage to the internal cable connecting screen to the computer's motherboard, a faulty graphics processor or ambient light sensor. Such problems are rarer on desktop Macs.
On Macs with a separate monitor, ensure the cable is securely connected to the correct port on both monitor and computer, and is not damaged, severely twisted or bent. If the cable includes tightening pins, use them to ensure a secure, consistent connection. Check that neither monitor nor computer ports are loose or damaged.
There may be an issue with software that controls screen brightness. Check for software that may deliberately cause the screen to flicker. Close or uninstall any software that is behaving erratically. Keep your operating system, OS X, up-to-date.
Attempting internal repairs, except by an Apple authorized dealer or repair service, might invalidate any warranty and cause further damage.
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