MacBook Pro - Screen "Blink" Fault

14th March 2010

This page is for Apple technical support; a quick unambiguous outline of the exact fault my MacBook has...

My 15" Unibody MacBook Pro (late 2008, 2.53GHz, 4Gb RAM) has an intermittent problem where the top of the screen "blinks" (flickers / flashes black) momentarily.

The most relevant thread on Apple's own forums pertaining to this problem has (to date) 598 posts, spanning 40 pages, most of which describe the same problem.

Below are four snapshots from consecutive frames of my video at: https://www.youtube.com/watch?v=Zxcnwi_mxK8. The video is 30 frames per second, and shows that the blink lasts for one whole frame and part of another, so lasts for about 1/20th of a second.

1	2
Screen as normal	Blink starts
3	4
Blink in full effect	Screen back to normal

Update #2

Sometime 2014?

Now the system will often crash/reboot if the newer NVidia 330M graphics system is activated. Some websites can even trigger this so just browsing the web is like Russian Roulette! This helps but does not totally fix it.

Update #1

January 2011

Apple gave me a replacement MacBook in April 2010, one of the latest models with the newer NVidia 330M graphics chip, and it's been free of this annoying blink problem.

According to Apple's own forum discussion on the problem (now up to 1005 replies and 150,000 views), the "blinking" issue still affects a lot of people with the 2008-era MacBook Pros, and I am still curious as to what the problem was. Below there are more screenshots from other videos of the problem. If anyone knows what causes this screen "blinking" problem, please contact me or write a post on the Apple forums thread.

My observations:

• The top of the screen blinks, can be anywhere between a few lines of pixels or all of the screen.
• Lasts about 1/20th of a second.
• Happens (only?) when using the NVidia 9400M graphics chip (by selecting "Better battery life" under "Graphics" in "Energy Saver" system preferences). I did not use the 9600M chip very much (it generated a lot of heat and made the fans run constantly), so I can't say for sure it would never happen when using that.
• Happens when plugged in to the mains and when running from battery.
• Using image enhancement on the snapshots, some of the screen content is still present in the blacked out area. Is this because my camera's CCD has not reacted fully to the screen turning black, or are the pixels still present on the screen (meaning only the screen's LED backlighting is switching off)?
• Timing (1): I could not detect a definite pattern, it seemed random. I made notes of the times and checked the system logs but nothing was apparent. After blinking it generally did not do it again for about 20 minutes. It tended not to happen after booting up the machine, only after it had been put to sleep (closing the lid) and woken up again. It would often happen within a few minutes after waking (when it was still cold, interestingly). Again, I rebooted it very rarely, mostly putting it to sleep every night, so can't be sure it would not happen after a reboot.
• Timing (2): After the fourth repair, with yet another logic board, the blinking soon started again and was worse than ever (contradicting my observations above). It started blinking a few times a minute, then stopped for a while (10-30 minutes) and started again. So different 2008-era logic boards exhibit the problem to different degrees.

Observations from the Apple forums thread:

• The blink can happen during boot, when the screen is grey (so it is not likely to be a software/OS issue).
• Putting the hard disk from a MacBook with the fault into a different MacBook does not transfer the fault. Again, this indicates it's a hardware problem.

Video #2

This is after the second repair job failed. (Not on Youtube.) The screen shows the MBP running the "top" command in a console to see if there is any unusual activity when the blink happens. It seems there isn't...

1	2
Screen as normal	Starts to darken (very slightly)
3	4
Blink in full effect	Screen returning to normal
5
Screen back to normal

Video #3

This is from Saturday 10th April, after the fourth repair failed, from: https://www.youtube.com/watch?v=OlQUOUURbiM.

1
Screen as normal
2
Starts to darken, from the top
3
Full blink (the light dash in the black area is a reflection of my camera).
4
Nearly back to normal
5
Screen back to normal