Screen flickering on new MBP

Discussion in 'MacBook Pro' started by klover, Jun 15, 2009.

  1. klover macrumors 6502a

    Jun 7, 2009
    Has anyone noticed a very slight flicker on their new MBPs? I have a new 13" and, every so often, the screen brightness dims and then brightens very quickly (happens in less than a second).

    The option for auto-adjusting the screen brightness is off so it's not that particular function.

    It's most noticeable on all-white backgrounds both on AC and battery power. Hard drive access doesn't seem to coincide with the dimming.
  2. spaceboots06 macrumors 6502a


    Jun 13, 2009
    The Rotten Apple
    I'm fairly certain there is another thread on this but what the OP of that thread said was that he called Apple and shipped his back. If I remember correctly.
  3. jgo78 macrumors 6502

    Nov 11, 2008
    yep, have this on my 2008 umbp 15", like a quick pulsing/strobing at low brightness levels. It's a common issue.
  4. henders98 macrumors member

    Jun 15, 2009
    I'm noticing the same thing when scrolling. It's especially apparent when browsing through threads on this site.
  5. jgo78 macrumors 6502

    Nov 11, 2008
    i think you're are talking about the tearing/distortion when scrolling issue. The other issue is when a static screen is just rapidly pulsing dimming in and out very quickly , a bit like a crt with a low refresh rate but not quite. I notice it when my screen brightness is very low, it pulses very quickly.
  6. klover thread starter macrumors 6502a

    Jun 7, 2009
    Mine's worse as I get the dimming at all brightness levels.
  7. jgo78 macrumors 6502

    Nov 11, 2008
    yea usually with mine, it stops being noticeable at half or greater brightness level. You might want to take yours back if it's that bad. I know it drove me nuts even though it wasnt that bad.
  8. delude macrumors 6502

    Dec 27, 2007
    Mine does this too on a lower setting, although I am worried about taking it back that the 'Geniuses' wont be able to see it.

    When you see the pulsing you could use the CTRL, SHIFT and EJECT combination to refresh the screen, which seems to help.
  9. jgo78 macrumors 6502

    Nov 11, 2008
    i tried that, doesnt seem to help me though however.
  10. klover thread starter macrumors 6502a

    Jun 7, 2009
    Tried that too but the flickering continues. It's a strange thing because I don't know what causes it. Sometimes it happens, sometimes it doesn't.
  11. nilblank macrumors newbie

    Jun 21, 2009
    Took my early 2009 MBP 15" in with exactly this problem. This has been a widely discussed issue with MBP screen particularly the 9C84 on the MBP 15". Not much actual information has been available about the problem--just frequent reports of similar experiences from owners. I went to see a Genius today and, apparently, Apple has an internal article circulating to the Geniuses recently that addresses this exact issue. It seems to be a issue with faulty logic boards and/or their frequency calibration to the screen. In other words, the logic boards are miscalibrated to the screen and send it frequencies that flickers slow enough for our eyes to see. If they have indeed solved this issue, then the 9C84 screens could wind up being a really amazing screen.

    They've ordered a new board for me and I'll be taking the MBP in to have replaced when it arrives. I though this was preferable to exchanging it for a new one that would very likely have the same or similar issue. My assumption being that, if someone sets out to specifically remedy this issue on my current system, my screen should be the flawless awesome screen we all expect of our MBPs.

    If the problem persists, I'll start playing musical Macbooks.
  12. upriver macrumors newbie

    Jun 27, 2009
  13. w00t951 macrumors 68000


    Jan 6, 2009
    Pittsburgh, PA
    I don't know, but on my old HP desktop, the display flickered like that because the display connector was loose and filled with dust.
  14. nilblank macrumors newbie

    Jun 21, 2009
    I read your post.

    Our experience seems very similar. I am also a recent PC-switcher. The benefit to my workflow has been quite satisfying but I find this issue with the screen inexcusable.

    I got my MBP back from apple care service today. They replaced the logic board apparently. However, the problem persists. It's worse sometimes, better others. But it is irritating overall.

    I'll probably call apple back shortly and ask some hard questions. It seems to me that this is becoming an increasingly common problem for mbp owners. if we continue to squeak, maybe apple will finally get around to oiling us. until then it seems the solution is to have apple "try" to solve the issue.

  15. jgo78 macrumors 6502

    Nov 11, 2008
    this is from someone who posted at apple discussions:
    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.
  16. upriver macrumors newbie

    Jun 27, 2009
    nilblank - thanks for your response. I'm intending to give Apple another call this weekend in the hope of getting an answer. There must be something about it in their knowledge base.

    jgo78 - Thanks, I have also seen that entry. I have also seen explanations that suggest that the PWM frequency is low enough that some people can perceive flickering/shimmering. Both explanations give hope to the idea that a firmware update may be sufficient to correct the problem. This is why I have held off returning the machine. Unfortunately if no firmware update is forthcoming then the situation remains.

    Can anyone else confirm that the problem still exists in the mid 2009 mbps (13" included)? I assume that it does.
  17. upriver macrumors newbie

    Jun 27, 2009
    Matte 17” Macbook Pro

    I see that there are rumours that Apple might reintroduce matte screen options for models other than the 17” Macbook Pro. Does anyone know whether the current 17” Macbook Pro with a matte screen has the same shimmering (flicker/shimmer, not ‘blinking’) issue as the 13” and 15” unibodys. I realise that it also uses led backlighting but wondering whether the different screen resolves the problem. If someone could test the 17” Macbook Pro unibody with a matte screen using the pattern I’d very much appreciate it.
  18. upriver macrumors newbie

    Jun 27, 2009
    I have been seeking a refund from Apple based on the display giving me eye strain and headaches (related I believe to the LED backlighting). They have declined, not because there is not a problem (they have not confirmed or denied a problem) but because the machine is 'in spec'. This appears to be par for the course for Apple. When you have a problem ignore it and hope that people won't pursue it.

    I do intend to pursue it further. I don't see why I should be out of pocket when the only thing I have done wrong is to buy an Apple machine.

    To assist me in pursuing it further could I ask anyone who has experienced eye strain and/or headaches from using the Macbook Pro to please contact me via email. Email address is mbp.displayproblem at gmail.

    All I will really need from you is a description of the symptoms you have experienced.

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