my external monitor is detected but doesn't work

Discussion in 'iMac' started by kyeol58, Aug 30, 2013.

  1. kyeol58, Aug 30, 2013
    Last edited: Aug 30, 2013

    kyeol58 macrumors newbie

    May 15, 2012
    Hi guys
    a little bit of a problem at the moment with a new 27" late 2012 imac.
    I am using the old mini display port connector that I used to use with my old 2010 macbook pro, and at that time it was running flawlessly.
    now that I connect it to the thunderbolt socket (potential problem?) it does not work. the guys at the apple retail store told me that it would work that way and that I didnt need to purchase anything else for it to work.

    oh and another potential source of problem is that I am using a dvi to vga converter as my external monitor only accepts vga. (yes it is old I know haha)

    so basically the set up looks either like:
    2012 imac (thunderbolt) -> mini display port-> dvi to vga converter -> vga cable -> external monitor
    2012 imac (thunderbolt) -> mini display port-> dvi cable -> dvi to vga converter -> external monitor

    both do not work.
    is this because I am not using a thunderbolt to vga/dvi peripheral
    or is it because the converter is not working? I have multiple of these converters but none work.

    Hope I've explained enough of the details, hope someone can solve this problem as no one in the apple store can tell me what I'm doing wrong. haha
    Thank you!
  2. macthefork, Aug 30, 2013
    Last edited: Aug 30, 2013

    macthefork macrumors 6502

    Feb 2, 2013
    I thought that Thunderbolt only put out a digital signal.

    The VGA monitor requires an analog signal. The older MBP would put both signals (DVI-I) on the mini display port dvi adapter and would pass through the analog signal to the the VGA monitor.

    Although Apple states the Mini Display port to VGA adapter works with Thunderbolt, there are a lot of people apparently running into this problem. (Check the Apple Discussion Forums)

    Have you tried the single Mini Display Port to VGA adapter sold by Apple to see how that works rather than running through multiple adapters? If it didn't work I would think you could return the adapter to Apple for a refund.
  3. kyeol58 thread starter macrumors newbie

    May 15, 2012
    thanks for the advice, I saw your message and just had a chat session with the apple store. They told me I needed to buy what you suggested to me, a mini display port to vga adapter.

    so basically my problem was that I am using a converter on a adapter?
    should that be a problem?
    I dont want to buy another mini display port adapter and end up with TWO useless adapters lol

    like you said I probably could get it refunded if thats the case though..
    I will head over to an apple shop soon and try it out and let you know how it goes

    Thanks again
  4. thekev macrumors 604


    Aug 5, 2010
    Apple sells some awful adapters. I know not only due to the reviews, but because I've purchased ones that weren't available elsewhere. A lot of people also mistakenly purchase thunderbolt cables for non-thunderbolt displays.

    Apple sells terrible adapters. Just read the reviews in the Apple Store. The quality control isn't there. My suggestion is a one cable solution. Mini displayport ---> vga in one cable, no ridiculous chain of adapters. The annoying thing with using long chains is that sometimes they don't work, and if one part fails you have to determine which one. You cannot use thunderbolt cables if it will connect to a non-thunderbolt display, even with the adapters. That's a common problem. The one I linked is technically mini displayport.
  5. SharkConsult macrumors newbie

    Oct 21, 2013
    South West Sydney
    Good Morning (AEST time) everyone!

    Just wanted to stop in this thread and bring it up again, I have a late MacBook Air (non retina) and I would like to connect it to my Benq 24" monitor.

    I previously had this monitor connected to my late 2013 iMac through a Thunderbolt -> HDMI cable. However, when I connect the cable to my MBA and the Benq, the MBA recognizes it, gives me the blue screen pause before screen mirroring starts, yet my monitor doesn't respond to the connection.

    History to the monitor and cable; Monitor was originally connected to a tower PC through a Display Port -> HDMI adapter, worked fine. Then was connected to a late 2013 iMac through a Thunderbolt -> HDMI adapter. It was then put back on a PC through DVI-D.

    The cable was taken and connected from the same 2013 iMac to another 24" monitor offsite. The cable has now come back and is connected to my MBA and the 24" Benq, the monitor doesn't want to know about it.

    When I attempt to 'change the channel' on the monitor to cycle it through VGA, DVI-D and HDMI, it reports that NO cables are connected.

    Any thoughts before I buy a new cable?

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