Electric shock reset clock/wireless/ shut off the computer?

Discussion in 'Mac Basics and Help' started by gatepc, Jun 14, 2010.

  1. gatepc macrumors 6502

    gatepc

    Joined:
    Apr 11, 2008
    Location:
    Pittsburgh PA
    #1
    I don't know if this is something to be worried about but I notice that when the tip of the display port cord ( from the ACD ) touches the metal frame of my MacBook Pro there is a tiny blue arch of electricity visible. Well, I just bumped that cord into the frame of the MBP and as soon as that happened the computer completely shut off, it just went to a black screen and turned back on when I connected it via AC outlet. When the computer started back up the clock was messed up ( 2008 date ) and it had forgotten all of my WIFI passwords.

    I was just wondering why this happens?

    And is it harmful?
     
  2. Makosuke macrumors 603

    Joined:
    Aug 15, 2001
    Location:
    The Cool Part of CA, USA
    #2
    Harmful: Could very well be. Do NOT do it again. Sounds like what happened was that the low-level firmware in the motherboard (that runs the clock) got hit hard enough by the shock to clear it, hence the reset. That should never, ever happen.

    It sounds like the MBP wasn't plugged in at all when this happened--is that right? And that the part that generates a spark is the outside metal shield on the small computer end of the connector, not any of the inner pins, correct?

    Based on what you're describing, you've got either a faulty piece of DisplayPort hardware, or seriously messed-up wiring in your house. The displayport connector does carry power, but it should only be power going to the device, not coming back from the other end. So even if something was badly shorted in the DP connector, it seems like you shouldn't get any kind of spark when touching the computer end of the cable to anything, since there's no voltage in it at that point.

    If, however, you have either a badly messed-up device on the other end of the DP cable (what monitor is it, specifically?), or the ground/neutral pin on the outlet that the monitor is plugged into isn't at ground potential, I could imagine a situation where that shield (which I assume is normally electrically connected to the rest of the cable and monitor shield, which is usually ground) was at some significant voltage. Now, if the computer wasn't plugged in at all, then I'd think the only current path through it would be through whatever it was sitting on (unless there was a USB hub cable plugged into the monitor already?), so I'd expect some substantial voltage to make a visible spark.

    The alternate possibility is that it was a static discharge, which could theoretically do what you described, unless it happens every time. Do you live in a very dry area, or usually have static problems?

    I wouldn't hook that monitor to anything until I got it figured out, lest you get unlucky and permanently damage the computer with a shock.
     
  3. gatepc thread starter macrumors 6502

    gatepc

    Joined:
    Apr 11, 2008
    Location:
    Pittsburgh PA
    #3
    The monitor is a 24" apple led cinema display it works fine once its connected and I don't get any sparking unless I bump into the aluminum cover of the MBP when trying to connect the display port connector. I live in California so yes it is very dry. My computer sits on an Mstand and yes it was on battery power when this happened. I do have powered usb hubs connected to the monitor.

    I don't know if this info is important but I have a lamp plugged into the same outlet and EVERY time I turn the lamp on for the first 2 mins or so it flickers ( and its not the bulb ) and then after about 2 mins the light stops flickering. I also have 3 extensions cords plugged into each other in a chain link ( I heard thats bad to do ... don't have enough outlets in my room )
     

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