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27" LED Cinema Display, no brightness control

2746 Views 10 Replies Latest reply: Jan 4, 2014 7:20 PM by TOAO RSS
dlisanto Calculating status...
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Feb 12, 2013 8:23 AM

I have a 27" LED Cinema Display that has the Mini DisplayPort cable and I am plugging into a MacbookPro 15" with a thunderbolt port. When I go into System Preferences there is no brightness control or ability to turn off automatic adjustment for the LED display, just the computer. I have the usb port plugged in as well. I have seen previous updates to fix this for earlier versions (10.6) but that didn't work on my OS X 10.8.2. Is there anything to remedy this? The automatic adjustment of brightness is very distracting and I would like to have control of the brightness of my monitor.

MacBook Pro, OS X Mountain Lion (10.8.2)
  • Malcolm J. Rayfield Level 5 Level 5 (4,510 points)
    Currently Being Moderated
    Feb 13, 2013 7:38 AM (in response to dlisanto)

    Open the disk image (.dmg).  If it does't open a Finder window, look for it in the Finder sidebar and select it. There should be a text file and the actual firmware updater.  You have to run the updater.

  • toddhac Calculating status...
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    Apr 4, 2013 4:04 PM (in response to dlisanto)

    Thanks, this solved my issue, had warranty repair done and got it back.  Before the repair there was a brightness slider, after I got it back, it was so dim I could barely see it.  Running this, solved it.  Download, run, unplug, wait 10 seconds, then go. 

  • Ben Grunfeld Calculating status...
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    Jun 10, 2013 2:08 PM (in response to dlisanto)

    This did not work for me. I read through all the instructions and ran the program, but no dice.


    Would appreciate any advice.

  • ski1stoney Calculating status...
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    Jul 8, 2013 7:30 AM (in response to dlisanto)

    This also did not work for me.  The button on the program is greyed out and it sayd "Connect LED Cinema Display (27-inch) to begin".


    The Cinema Display is connected and I am currently typing this note on the Cinema Display.


    I too would also appreciate any advice.

  • TOAO Level 1 Level 1 (0 points)
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    Jan 4, 2014 12:40 PM (in response to Ben Grunfeld)

    This portion of the AHT will repair no brightness control on a repaired monitor and actually is required when repairs to the internal logic board are performed.

    HOWEVER !!!!

    It is not noted or emphasized that for this to work properly OR for brightness control to work properly, the monitor USB cable MUST be attached.


    There is no brightness control without the monitor USB cable attached and there is not supposed to be.

    In short, make certain the monitor USB cable is attached befire running this repair tool or trying to control brightness.


    It is also worth noting that the 27" LED Cinema DisplayPort equipped monitor HAS problems with monitor USB connections.

    This is due to the anodization of the chassis. (anodization produces non conductivity)

    Make certain the USB connection is made before trying anything else.

    Do this by using a keyboard or mouse attached to the monitor USB ports.

    If there is no connection (as silly as this sounds) try wiggling the USB cable at the rear of the monitor until a connection is made.

    This makes and breaks ground momentarily and typically re-establishes USB connection.

  • TOAO Level 1 Level 1 (0 points)
    Currently Being Moderated
    Jan 4, 2014 1:26 PM (in response to ski1stoney)


    See previous.


    It should also be noted that another setting should also be attempted.

    Go to system preferences Sound and choose an Output option other than monitor USB (Display Audio).


    For those who use wireless keyboard and or mouse the monitor USB connection must be verified by some means. Sadly, this may mean that your only verification is use of Display Audio as the Sound output.

    In any case, make certain that the monitor USB connection is made through one means or another. (try a thumbdrive)

    In some cases selecting Sound output as something other than Display Audio can help clear up a USB conflict.

    (don't forget to try a restart after changing settings)


    The no brightness control condition varies from computer to computer.

    For example, this problem on a Mac Pro appears as no Brightness control slider at all and no Auto brightness adjust check box at all.

    For others this may appear as grayed out.


    If you have followed ALL these simple steps, there is a possibility that your monitor has a logic board problem that can only be verified through use of an AHT** if you are lucky enough to have one or.... Apple ASD which is only available at a service center.

    (**NOTE: Apple has discontinued use of the AHT due to limitations that failed to diagnose problems.... don't quote me please!.... but I believe the AHT was discontinued in 2010 for most models)

  • TOAO Level 1 Level 1 (0 points)
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    Jan 4, 2014 7:20 PM (in response to Ben Grunfeld)



    It’s possible that the issue might simply be resolved when applying both a Software and a Firmware update for the LED Cinema Display. If you haven’t already, please download and install the following to see if these updates resolve the issue:


    Secondly, if you are using Mac OS X 10.8 (Mountain Lion) or Mac OS X 10.9 (Mavericks), please try this additional Software Update for the LED Cinema Display if you haven’t already installed it:


    Additionally, my research into other customers’ cases with these issues (brightness controls and USB functions not behaving correctly) regarding the LED Cinema Display shows that the following method might fix your issue: When connecting the affected LED Cinema Display into your Mac Pro, first plug the USB connector into the Mac, then plug the Mini-Display connector into the Mac, and finally re-open System Preferences to see if the brightness controls have returned.


    That mentioned just previously is worthless for those with an updated operating system but is mentioned regardless.

    As it works out those installers will not allow installation and merely state that you don't need this software in updated systems.

    They require that you make a brand new OS installation to be of any effect and are included in Software Updates.

    They are worth a try if all else fails.


    You should also try Disabling your Bluetooth "Discoverable" setting.

    The Discoverable Bluetooth setting seeks to establish a wireless USB connection and depending on your RF environment, can become very busy if not conflicted. (can override a wired USB connection)


    Last but certainly not least.

    Do NOT connect your monitor USB through a USB hub.

    Internally your monitor has a USB hub.

    Connecting a USB hub TO a USB hub is just asking, (if not blatantly begging), for problems.


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