External Hard Drive Not Showing

Discussion in 'Mac Basics and Help' started by sgtbob, Mar 20, 2009.

  1. sgtbob macrumors regular

    sgtbob

    Joined:
    Sep 10, 2008
    Location:
    Kansas
    #1
    I have a Toshiba 160 GB USB external HDD (no power supply required) that I use simply as a backup for some Windows programs when I am using my virtual machine. It required a double USB cable and its icon showed on both the Windows and iMac screen until a day or so ago. It is a functioning unit when I put it on a separate PC. I have not been able to correct the problem and in viewing some of the forum items I keep seeing suggestions to view the 'System Preferences --> general' - I do not see a 'general' nor any reference in the 'apple' that refers to hard drives (external or internal). What am I missing here?

    Bob :confused:
     
  2. BlueRevolution macrumors 603

    BlueRevolution

    Joined:
    Jul 26, 2004
    Location:
    Montreal, QC
    #2
    So you mean that it still works, just not while connected to your Mac?

    Where are you seeing suggestions of this "General" section in OS X? The only version of the OS I haven't used is 10.2 Jaguar, and I have never seen a General pane in any other version. It's not just you.
     
  3. sgtbob thread starter macrumors regular

    sgtbob

    Joined:
    Sep 10, 2008
    Location:
    Kansas
    #3
    Not exactly sure what occurred, but I switched the two ended USB cable slots and the machine now recognizes the 160 GB external drive. I hate it when a fix happens and I don't know why.... :)

    Thanks for the post.

    Bob
     
  4. plucky macrumors newbie

    Joined:
    Mar 19, 2009
    Location:
    UK
    #4
    I have the same problem with an external USB HDD of 80GB. The problem is that these HDDs require somewhere between 180 and 250 milli-Amperes of power to run. Particularly older ones need more curent. A USB port can only provide a maximum of 200mA of curent (that's the USB standard).
    If you plug it in a USB hub that is not powered, like the Mac Keyboard, they do not have enough power provided to them.
    This is why you use the USB cable with 2 plugs, that provides twice as much power to the HDD and so they are fine.
    Alternatively if you plug directly to the computer or a powered hub they are ok.

    Hope this clears the mistery... :)
     

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