Late 2012 iMac USB issues

Discussion in 'iMac' started by digitalfailure, Mar 1, 2013.

  1. digitalfailure macrumors regular

    Joined:
    Sep 24, 2012
    #1
    Hi all

    I have a 27" new model iMac with the wired keyboard that's being a bit odd when my 4s is plugged into the USB port on the keyboard.

    The machine will often flash up a warning dialogue saying a USB device has drawn too much power, and that the USB ports have been disabled. Sometimes the message will flash up 4 times at once :(

    If I unplug the phone and reconnect it again straight away the USB works correctly. Plugging in my iPad or a cf card reader to the same port doesn't give the message so I don't know what to think.

    Anyone else had random USB issues on new iMac ?
     
  2. macthefork macrumors 6502

    Joined:
    Feb 2, 2013
    #2
    That wired keyboard is USB 2.0, and the keyboard itself draws power, too. Try plugging your devices into the USB 3.0 ports in the back of the computer or get a USB 3.0 powered Hub.
     
  3. digitalfailure thread starter macrumors regular

    Joined:
    Sep 24, 2012
    #3
    That's the strange thing, my 2008 imac had the same keyboard and the same phone plugged in and I never got the message :confused:

    A powered usb hub might be the way to go
     
  4. WilliamG macrumors G3

    Joined:
    Mar 29, 2008
    Location:
    Seattle
    #4
    That sounds very odd. Are you using a third-party iPhone cable, out of interest?
     
  5. Lancer macrumors 68020

    Lancer

    Joined:
    Jul 22, 2002
    Location:
    Australia
    #5
    Very odd, I've never plugged the phone into my KB, maybe that's for the best?
     
  6. digitalfailure thread starter macrumors regular

    Joined:
    Sep 24, 2012
    #6
    No, it's the standard white USB to 30pin iPhone cable that came with the phone.

    I've plugged the 3, 3GS and my iPads into the keyboard before on my old iMac and not had the warnings, and even when I plug my iPad 3 into the keyboard on this iMac I don't get a warning. Ok it doesn't charge the iPad but it still communicates with iTunes ok.
     
  7. FreemanW macrumors 6502

    Joined:
    Sep 10, 2012
    Location:
    The Real Northern California
    #7
    digitalfailure: Doc, it hurts when I do this.

    Doc: Don't do that.

    Okay, seriously, you have apparently discovered an idiosyncrasy in the new iMac. It is USB 3.0, unlike the previous (earlier) USB 2.0 macs.

    Just don't plug USB devices that impose a current draw into your wired kb. ;)
     
  8. digitalfailure thread starter macrumors regular

    Joined:
    Sep 24, 2012
    #8
    But that's not right!

    My understanding is that the first device plugged in sets the USB level, so a USB 2.0 keyboard brings all the USB ports down to USB 2.0

    USB 2 will charge an iPhone, so it shouldn't be having issues. If the USB was staying at 3.0 , there should be an even greater current supplied so even less chance of the issue.

    It's also totally random and intermittent, which wouldn't be the case if it was a genuine over current situation as that would be repeatable on demand.
     
  9. WilliamG macrumors G3

    Joined:
    Mar 29, 2008
    Location:
    Seattle
    #9
    I agree with you there. Have you tried a different iPhone cable? Just trying to rule things out.
     

Share This Page