Are cheap USB hubs grounded?

Discussion in 'MacBook Pro' started by steffi, Apr 20, 2009.

  1. steffi macrumors 6502a

    Joined:
    Jun 7, 2003
    #1
    So, I have a cheap 7 USB hub (runs on AC) that I bought in Asia and in general it works quite well but the thing I don't like about it is if I touch the outside of it with my finger often it shorts ie. drives that were connected to it are no longer connected and my EyeTV quits and has to be restarted.

    ...

    Q. Is this typical of a cheap vs a branded hub?

    Would a branded hub work this way?
     
  2. m85476585 macrumors 65816

    Joined:
    Feb 26, 2008
    #2
    Even a cheap hub shouldn't do that.

    Is there a static discharge when you touch it? If you touch a grounded piece of metal first (like your MBP as long as you are using the grounded 3-prong cable), then touch the USB hub, is it still a problem? If you isolate yourself from ground (don't touch anything metal, wear rubber shoes or lift your feet off the floor, and don't sit on a metal chair) does it still happen?

    It could be a bad power supply that came with it, or the hub could be bad.

    These would be good choices for about $20:
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817111402 (with rebate)
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817182057
     
  3. steffi thread starter macrumors 6502a

    Joined:
    Jun 7, 2003
    #3
    Yes there usually is a static discharge when I touch it.

    It's a matter of getting into that habit.

    The power supply for the hub is the 2 prong Nokia phone adapter style. It's possibly even the same adapter.

    I actually owned that DLink Hub in the past but they have a single voltage adapter and it's very difficult to find a replacement when you travel.

     
  4. m85476585 macrumors 65816

    Joined:
    Feb 26, 2008
    #4
    If you discharge any static before touching it, does that help? Also try using the grounded 3-prong adapter for your MBP since that will give the static a safe path to ground. USB hubs should be grounded to your computer by the USB cable, specifically the metal connector, the shield braid, and one pin inside. If your computer isn't grounded to the wall, the static has nowhere to go and can cause problems.

    One time I touched the outside of my aluminum hard drive, and the static discharge caused it to shut down (luckily there was no damage or data corruption). Also, I have temporarily killed my trackpad and keyboard with static (it didn't work until I used my bluetooth mouse to reboot). I've gotten into the habit of touching something grounded or the body of my computer after sitting down before touching anything else to avoid problems.

    It looks like almost everything that attaches to a computer is not grounded to avoid ground loops. Basically, there has to be just one central ground connection with every device connected to that. By not using the grounded (3-prong) cable with the MBP, none of the connected devices have a proper ground, which can be a problem if there is a static discharge or something. Too bad Apple can't make a grounded travel adapter.
     

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