14 Replies Latest reply: Oct 28, 2007 2:44 AM by Guy Reid
iedutu Level 1 Level 1 (35 points)
First of all, please note the below procedure is to be tried at your own risk.
The basic idea is to add a custom refresh rate to the system (70Hz Vertical) and use it instead of the default one (60Hz).

What was my flicker like:
Continuous, felt like watching and old TV (European, 60Hz) and feeling the ripples. I had no sudden changes of backlight intensity, and the flicker became obvious when using a matte background image, usually grey or blue.

What I had done:
While searching for any clues on how to check/modify the display refresh rates, I found a thread (really sorry for not putting the link ... forgot it) where the poster recommended a small program (SwitchResX Control) to create a poll of faulty LCD manufacturers. I have downloaded the software and finally I managed to fix my flicker

Step 1:
Get the program at http://www.madrau.com/switchres/SwitchResXControl.zip. You should use the native resolution for the MacBook (1280x800).

Step 2:
In the program, go to the Custom tab. Press the + sign to create a custom setting. In the 'Timing Parameters' window, after making sure all the parameters are the same as the normal 1280x800 setting, set the vertical scan rate at 70. Also, check the 'Positive synch' check-box. Save everything and reboot.

Step 3:
Open System Preferences, then Displays. Now you should have the Refresh Rate drop-down option enabled (should be 60). Select the 70 setting. Save and reboot.

Step 4:
You should have a flicker-free display now.

Feel free to check http://www.iedutu.net/macbook for pics taken during setup and settings from my machine.

Please remember:
0. If anything goes wrong, select Factory Settings, save and reboot.
1. This thing worked fine for me. It might not work for you. If you have done all steps and still have a flicker, you might have a genuine hardware problem. Like I mentioned before, I did not have an extreme type of flicker, nor a random one.
2. This should be tried at your own risk. I think setting a different refresh rate cannot damage your hardware, but I'm not a hardware guy, therefore I hope nothing will go wrong with my MacBook too .

Have fun!

Black MacBook 2.16Ghz, 2Gb RAM, Mac OS X (10.4.10), 1 dead Adapter until now ...
  • 1. Re: I have just fixed my screen flicker (Software only)
    walter59 Level 1 Level 1 (0 points)
    dear cristian,

    i have just followed your instructions concerning the flickering of my screen. Obviously it works! Thank you


  • 2. Re: I have just fixed my screen flicker (Software only)
    iedutu Level 1 Level 1 (35 points)
    I'm glad to hear it worked for you also.
    I just hope Apple will add some other refresh rates to the MacBook screen as well, by default, as it seems the LCD can go over the 60Hz barrier.
  • 3. Re: I have just fixed my screen flicker (Software only)
    Alex Zakrevsky Level 1 Level 1 (5 points)
    It worked for me as well!
    I have a brand new MacBook, that had a screen flickering. I've done what you suggested. Changed refresh rate over to 70. Reboot. And here it is, no screen flicker whatsoever.

    Thank you!
  • 4. Re: I have just fixed my screen flicker (Software only)
    Technarch Level 1 Level 1 (10 points)
    iedetu, why do you recommend 'positive sync'? the 60 hz rate uses negative/negative. I tried 70 hz with negative/negative and it works fine but not for the flicker problem I have.. I have an original core duo yonah macbook, so I am not affected by the core2duo flicker. Just wondered why you specified positive sync.

    Doesn't fix backlight issues unfortunately.
  • 5. Re: I have just fixed my screen flicker (Software only)
    iedutu Level 1 Level 1 (35 points)
    I have just tried with the 'positive synch' option disabled, and it works fine. I am actually working on 75Hz now

    The reason I put it was a 'trial and error' process I took the day I found it worked. Basically, it seemed to make a (slight) difference.

    Actually, this is better from my point of view. The smaller the change to the default system, the better.

    Thanks for the comment!
  • 6. Re: I have just fixed my screen flicker (Software only)
    Dubdog Level 1 Level 1 (35 points)
    Thanks for the tip. I've already had the inverter changed for screen flicker several months ago so was disappointed when it seemed to reappear (although not as bad as previously and it wasn't continuous). This looks like it's done the trick but, as I say it wasn't continuous, so I'll have to give it a bit of time and if I get a hint it hasn't worked I'll post back here to let you know.

    Thanks again.

    Message was edited by: Dubdog
  • 7. Re: I have just fixed my screen flicker (Software only)
    Paul J. Hart Level 1 Level 1 (80 points)
    Well, i tried this fix earlier today and all day, no flicker

    However, as i type this message the flicker is coming back so I am afraid its not a permanent solution at least not for me!
  • 8. Re: I have just fixed my screen flicker (Software only)
    Dubdog Level 1 Level 1 (35 points)
    Same here, my flicker back so this isn't a permanent fix (and as the flicker is intermittent it's difficult to say whether it was fixed in the first place).

    Just contacted Apple UK who first tried to suggest the flicker was normal to which I replied that my machine has been fine since the inverter was replaced a while back but now the flicker has returned (all be it not as bad as previously). After running some trouble shooting that didn't sort the problem it's now going to be booked into an Apple Service centre.
  • 9. Re: I have just fixed my screen flicker (Software only)
    iedutu Level 1 Level 1 (35 points)
    I looked over a number of mac forums and I can say that there are two separate flicker problems:

    1. Continuous flicker, obvious on a blue/gray wallpaper when dimming the brightness. Flicker not visible on full brightness, growing while dimming the display. At 50% brightness the display is very usable, flicker visible only if you are actually looking for it. My take this is a software problem (found few people saying the flicker is gone in Windows XP in bootcamp, but present in OSX).

    2. Random flicker, ranging from almost visible to flashing screen. Comes at random times, with or without the power adapter plugged in. Can appear in all sorts of combinations/situations. I do not want to assume anything here, but I feel this is a hardware problem based on the YouTube clips I saw.

    My case was the first one, thank God and hopefully it will stay like this, although I saw MacBooks on display with no flicker whatsoever.

    On the second case, I think a trip to an Apple Service Center would fix it. Unfortunately there is no known faulty module that changed is fixing the problem for everyone with the random/continuous flicker. Everything from logic boards to invertors to displays were changed with mixed results. But it seems the invertor is being changed in most cases and most people are happy with the result.

    My 2c.

    Have a nice day!
  • 10. Re: I have just fixed my screen flicker (Software only)
    Dubdog Level 1 Level 1 (35 points)
    Thanks for you input Cristian. Didn't mean to sound ungrateful in previous comment. I'd give you a 'helpful' if it had been my post originally.

    Hope your MacBook stays trouble free.
  • 11. Re: I have just fixed my screen flicker (Software only)
    Ste Thornley Level 1 Level 1 (0 points)
    Cheers Mate, this worked a treat, cant even see the wave now on the Grey Apple start up screen. Also I cant see any side effects, at 1st I thought the screen looked a bit blurred but I think that was down to my Tired eyes, typing this msg now and the screen looks amazing, one of the best screens i have ever seen.

    many Thanks for the excellent advice

  • 12. Re: I have just fixed my screen flicker (Software only)
    iedutu Level 1 Level 1 (35 points)
    I am glad to see the fix working for others too.

    I believe there is a difference on my gray booting screen also, therefore I can only assume that somehow the refresh rate set by the OS is registered hardware (like in the PRAM) after a change. If so, I think the entire system is using the last set rate, thus the change in the booting screen.

    It might be of use if somebody who had the continuous flicker problem and has fixed it with the procedure described by me has seen any changes while running Windows (XP or Vista) under bootcamp (without tempering with the Windows display driver's settings). I have absolutely no use for Windows on my Mac, therefore I tend to keep it away

    Good luck!
  • 13. Re: I have just fixed my screen flicker (Software only)
    iedutu Level 1 Level 1 (35 points)
    Marked 'Answered'.

    Hope some filter will send this to Apple
  • 14. Re: I have just fixed my screen flicker (Software only)
    Guy Reid Level 1 Level 1 (30 points)
    SwitchResXControl worked for me in Tiger. Doesn't seem to in Leopard. In fact it even crashed on startup once.