Bad grounding on external keyboard causing me to get shocked...

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Bad grounding on external keyboard causing me to get shocked...

I have a mid '09 Macbook Pro (13 inch), and attached to it I have an external keyboard, the aluminum one with the numpad.

When it's plugged in to my USB hub, I noticed that whenever I would put one foot on the heating pipes (that run right past my foot, nice for cold feet in the winter) and touch the keyboard on the left side, between the shift and the caps-lock button, I would get shocked. It would slowly build up, first causing a tingle in my finger, ending with the keyboard actually being painful to hold and my hand to cramp up a bit.

Doing some experimenting, I found out that if I didn't have my foot up on the (metal) pipe, all would be well. Simple fix, one would say. But it still worries me. Especially since I have the same when it's plugged into my Macbook. A badly grounded cheap-o powered USB hub that's a few years old, fine, but my new Macbook?

My question here is, is there something easy that I can check to see if the grounding problem is in the keyboard itself, or in the hub/Macbook? I don't have an other aluminum keyboard I can plug in, nor do I have something else with a metal case and a USB plug.

Mid '09 Macbook Pro 13 inch, Mac OS X (10.6.1)

Posted on Oct 8, 2009 2:23 PM

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Answer 1

red_menace

Level 6

17,066 points

Oct 8, 2009 8:20 PM in response to GooneyBird

The MBP power cube puts out less than 20 volts (the USB hub would be similar, if not less), so I would be curious where the "painful" part is coming from. Using these kinds of power supplies also tend to isolate the power from the receptacle, since there isn't a direct connection to the equipment chassis like a desktop.

If you have access to a meter, you can measure the voltage between the pipe and the keyboard chassis. Another thing to check is that the receptacle is correctly wired (you can also try moving the power connection to different receptacle).

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Answer 2

Oct 9, 2009 1:59 AM in response to GooneyBird

It's most likely an ungrounded outlet. My laptop has shocked me a few times when using an ungrounded outlet. Plugged it into a properly wired outlet and no more shocky.

Also try it in a GFCI outlet (Commonly found in bathrooms)
And then touch something metal (The same pipe if possible, or something grounded) while touching the part that's shocking you. If the GFCI outlet breaks the circuit, it's likely an electrical issue with one of devices itself. If not, the outlet in your room likely needs to be serviced by an electrician. Though this test isn't bullet proof.

Hope this helps determine what's wrong.

EDIT: Said outlet 6 times! Er make that 7

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