Electric shock from touching peripherals

Discussion in 'Mac Pro' started by hangrat, Dec 12, 2016.

  1. hangrat macrumors newbie

    Jul 10, 2012
    For the last week one of our 2013 Mac Pro's has started randomly shocking you a few times a day when you touch it's peripherals, so far it's happened with both a pair of headphones and a usb mouse, both have been in use on the system for several months.

    So far I've only had time to try an SMC reset but that didn't resolve the issue. Any ideas of what might causing this and how I fix it? Thanks!
  2. ActionableMango macrumors G3


    Sep 21, 2010
    You're getting a shock from touching plastic peripherals?
  3. sigmadog macrumors 6502a


    Feb 11, 2009
    near Spokane, WA
    Usually in cold weather I'll get shocks when I touch metal parts. Static electricity. I can usually dissipate the charge by first contacting my knuckle on something grounded before touching the electronics. What works well is the tiny screws holding the light switch cover plate to the wall.

    I suspect that's what's causing your issue.

    Either that or you computer is about to explode. Kidding.

    Other than that, you might try switching peripherals to see if the problem persists.
  4. JoelTheSuperior macrumors 6502


    Feb 10, 2014
    London, UK
    Could be that the Mac Pro isn't grounded properly - check that you're actually using an earthed power cable.
  5. thefredelement macrumors 65816


    Apr 10, 2012
    New York
    I once worked on a rack mounted system that was plugged into an outlet that wasn't properly grounded, the rack was carrying 120V!
  6. Ph.D. macrumors 6502

    Jul 8, 2014
    Exactly. The Mac's power cable has a three-pronged plug, does it not? Are you by chance using an extension cord or an adapter at the end that somehow bypasses the ground terminal (the round one in the U.S.)?

    Another possibility is a so-called "ground loop" in which multiple devices (computer and a printer or monitor, let's say) have separate grounds that meet up in the middle, such as through an interconnect cable, resulting in a miss-match and a current that flows through the loop. This is somewhat unlikely, but the first approach to fixing it would be to plug both devices into the same outlet. That reduces the likelihood of a mismatch in grounding.
  7. AidenShaw macrumors P6


    Feb 8, 2003
    The Peninsula
    This is key.

    Is the "shock" a brief "zap" when you touch something - or is it a prolonged "zzzz" that lasts until you let go of the thing?

    If the former, it's probably just environmental static electricity due to low humidity.

    If it's the latter, you have a serious power supply or grounding issue that needs to be addressed before it kills you.
  8. hangrat thread starter macrumors newbie

    Jul 10, 2012
    Thanks for all the replies everyone!

    The Mac Pro runs into a UPS, via a 3 pronged plug and the UPS connects to the wall outlet.

    Unless a UPS can cause a grounding loop I think that one might out of the mix.

    The peripheral have been plastic although I think the headphones might have had a metal band.

    It was a short shock, not a sustained buzz but it really didn't feel like a static shot.

    For now I guess I'll ask the user to ground themselves before touching it and bring in a plug tester to make sure the outlet doesn't have an issue.
  9. Ph.D. macrumors 6502

    Jul 8, 2014
    No doubt the UPS has a 3-pronged plug too? You might experiment and plug the Mac straight into the wall for a day or two and see how it fares then. (Most consumer-grade UPS's are junk.)
  10. hangrat thread starter macrumors newbie

    Jul 10, 2012
    Yup, 3 prong from the UPS to the wall as well, but I'll definitely try swapping for another to see if the issue resolves.

    If you don't have a UPS you like you should try cyberpower, I've probably a bought 40 of their 1500va model for various facilities in the last 8 years and at least so far haven't had a problem with a single one. That said this batch is the first update to the model I buy in years so maybe wait till i figure out if it's the UPS or not ;)
  11. hangrat thread starter macrumors newbie

    Jul 10, 2012
    Alright, it looks to have been static all along, generated by the mesh backed chair the user was sitting in. No shocks since removing the chair and we tested the outlet so static seems pretty confirmed.

    Thanks for the help everyone!

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