Previous 1 6 7 8 9 10 11 Next 162 Replies Latest reply: Dec 15, 2009 2:29 AM by saledan Go to original post
  • Aunty June Level 1 Level 1 (105 points)
    oh, that's not good.
  • William Rivas Level 5 Level 5 (4,240 points)
    Jeff Storm wrote:
    Anyone get a definitive yet on the MBP screen flicker issue?
    Travel back to the Apple store or wait for update?
    Got a new 2.8Ghz and when it wakes up from sleep the their is a slight flicker you notice especially on a more solid desktop image.

    After several minutes it seems to reduce but is still noticeable enough to be annoying.

    Try resetting the screen by holding control, shift and eject. the screen will go black, hit any key and this should resolve the issue. I have 2 newer 15" 2.53's. Worked for me.


  • aghbo Level 1 Level 1 (0 points)
    try this site to test at high intensity levels. You can see the screen flickering on the sides.

    You will see it even on main power.
  • darrylh Level 1 Level 1 (5 points)
    Hopefully I can shed some light (no pun intended) on the backlight flickering issue at low brightness. I have designed fpga controllers for LCD panels, and the issue is a combination hardware/firmware issue.

    I purchased a uMBP in October and never saw any backlight flickering at low brightness with either GPU. I just received a newer uMBP and it shows the backlight flicker problem only on the 9400. It was immediately obvious what the problem is. The LCD panel has an underlying repetition rate as does the LED backlight controller since it uses PWM techniques to dim the lamps. Apple did not provide enough filtering on the LED PWM controller so the LED's are actually slightly flickering on their own at the rate of their PWM controller. This is not a problem on it's own as the PWM frequency is always high enough that the human eye can not perceive it. The problem is when this frequency or it's harmonics are close a frequency of the LCD, patterns will be created in the light intensity called beat patterns. Since these beat patterns are dependent on the absolute frequency of the LCD and LED PWM, and since each GPU and the LED PWM are sourced from different clocks, the issue will be different for every motherboard, and will vary with such things as voltage and temperature.

    I verified my suspicions by slightly shifting the operating frequency of the LCD (not something anyone can do) and the problem went completely away. As I continued to change the frequency the problem would reoccur and subside as the two fundamental frequencies would beat against each other.

    The solution would have been to provide better filtering of the PWM supply, but this is a typical trade off that even I would have made when designing a PWM dimming circuit. Also, typical white LED's have a fairly slow response time, so this was probably relied upon for some of the filtering. The other solution is to just shift the frequency of the LCD or LED PWM so that they don't beat. The problem here is again with the absolute frequency (over time, temp and voltage) on each motherboard.

    So the bottom line is an LCD replacement will not affect this issue at all (although it may address some of the other issued raised in this thread), and a motherboard replacement is a hit or miss proposition at best, (unless Apple has made a hardware changed, but based on my new uMBP, they haven't) and even if it does appear to fix it at first, it may return later. My guess is (and this is only a guess) a firmware change could be made to shift the clocks to alleviate this problem. This is something I have done to my firmware designs, but is not always possible for other engineering reasons. Certainly the LCD clock rate can be shifted easily, but what complicates the solution is it needs to be universal across all notebooks and that can be a difficult thing to achieve.

    So can anyone confirm that they have spoken to someone at Apple that has confirmed they know of the issue and are actively seeking a solution? Without this confirmation, I don't intend to send my MBP back as it can be a futile exercise as pointed out by others in this thread.
  • Aunty June Level 1 Level 1 (105 points)
    thanks, this is very good information. I experience this low brightness pulsing/strobing when my 9400 is cold but once it warms up after a few minutes, the flicker goes away. The 9600 is opposite, when it's cold it's fine, when it gets hot ie) running the the cpu/gpu at close to full load the flicker/strobing appears, again at low brightness levels. I haven't taken it in because I see by your explanation it's a complicated issue. So, I guess we have to live with it? or take it in and hope that someone with your knowledge notices it and is able to fix the problem.

    I can say however, that I bought a brand new 17" mid June umbp and does not flicker at all under any circumstance. Just too bad my 15" October umbp has this problem.
  • darrylh Level 1 Level 1 (5 points)
    Sorry to hear your 15" is doing this Aunty June. Just like your 17", my original 15" from last October has never shown the pulsating issue either, or at least not enough to notice. As you have seen, it can be heat related among other things, so a motherboard swap may or may not work. If it bothers you enough you can certainly try a swap, but be prepared for it be the same, or perhaps occur under different circumstances, or maybe even be better. There's just no way of telling. I have found that running mine over 50% is usable as far as the pulsating goes, but it sure would be nice to have it corrected.

    I am going to try to push Apple Support to get a definitive answer from engineering. I used to be an Apple developer so I will try contacting some engineers I used to work with, but that was a long time ago and I fear they may not be there anymore.
  • Aunty June Level 1 Level 1 (105 points)
    great, please keep us posted.
  • Wouter Level 1 Level 1 (0 points)
    Hi All,

    I am too,having the problem that on occasions, my screen flips to black and back to normal within a second.

    I have an unibody Macbook Pro 15" acquired november 2008. Strangely enough I started noticing it not before an upgrade to 10.5.7

    I have contacted my Apple Store through email and will keep you posted on progression.

    Cheers !

  • Geoffrey Bender Level 1 Level 1 (0 points)
    Thank you for posting this video. I thought I was going crazy because it happens so fast. I have this exact issue.
  • eww Level 9 Level 9 (52,975 points)
    darrylh: It sounds to me as though you would be the perfect person to engage Apple's engineers in a conversation about this issue that affects a good many MBP users. I wouldn't expect Apple to try to fix all the machines that flicker, but perhaps a design tweak in the next generation would result. Thanks very much for taking the trouble to explain the matter to us, whether or not you go on to try to explain it to the appropriate people at Apple.

    I'm flagging your post in the "Notable New Technical Issues" area to bring your explanation to the attention of the Discussions hosts, who can then point it out to the engineering folks.
  • Graphsic Level 1 Level 1 (0 points)
    I have a brand new Macbook Pro 15" 2,8GHz model.
    Bought it just yesterday and I experience the same problems.
    Although I mainly have the flickering issue with scroll my bookmarks in safari or my application stack in the dock.

    I've recorded it and it can be seen here:
  • Jottle Level 1 Level 1 (70 points)
    Graphsic wrote:
    I have a brand new Macbook Pro 15" 2,8GHz model.
    Bought it just yesterday and I experience the same problems.
    Although I mainly have the flickering issue with scroll my bookmarks in safari or my application stack in the dock.

    I've recorded it and it can be seen here:

    That looks more like the flickering spotlight bug that appeared in 10.5.7. See this link:

    Do me a favor. Does this flickering appear when your laptop is plugged in, or does it only happen on battery power?
  • Graphsic Level 1 Level 1 (0 points)
    It happens only on battery power. But, I've seen it once when it was plugged in with the power cord.
    It does not happen when I boot in safe mode. Do you have a solution? that would make my day!!!!
  • Graphsic Level 1 Level 1 (0 points)
    It is not a spotlight bug since I don't have it when I type in the spotlight search window at the right top.

    I experience it when scrolling in a menu like stacks in the dock or the bookmarksbar in safari. Then I see parts of the underlying layer popping up. (like you see in the movie).

    What should I do? I still can return my MBP and get my money back and order a new one (i'm still in the 2 weak period after buying). Or should I wait for a software fix? I'm affraid that it can't be fixed with just a software update....
  • Jottle Level 1 Level 1 (70 points)
    Sorry. I don't have a solution. If I were you, I'd try to go into an apple store and create a big stack on some of the display mbp's on the sales floor. If you can get these macs to exhibit the flickering while on battery power, then it's safe to say that's it is a software issue.
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