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How can I avoid my MacBook Pro giving me minor shocks?

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Re: How can I avoid my MacBook Pro giving me minor shocks?

#51

Post by pmoriarty »

jordwest wrote: post #18

What's fascinating to me about this phenomenon is that you can actually feel the 60Hz AC by running your hand across the lid. It feels as if the surface is slightly bumpy, but the width of the bumps changes as you adjust the speed your finger moves. Unplug from mains, and the surface becomes smooth. As the answer notes, this only happens when using the two-prong adapter without earthing. It also seems to be more noti…

I felt this on an Apple laptop in California a couple of years ago, in an apartment with only two-prong outlets in it. I'd describe the feeling more like the laptop cover was vibrating, rather than bumpy. The feeling went away and the laptop cover became smooth and normal if I lifted my feet off of the ground.

Once all the outlets were rewired to be three-prong, with ground, I used a three-prong power cord and the problem went away.

Pretty scary feeling, and scary to think that two-prong outlets and appliances are legal anywhere. I'd also be surprised if Apple hasn't been sued at some point by someone getting electrocuted when using their laptop and a non-grounded, two-prong power cord.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#52

Post by djsumdog »

jordwest wrote: post #18

What's fascinating to me about this phenomenon is that you can actually feel the 60Hz AC by running your hand across the lid. It feels as if the surface is slightly bumpy, but the width of the bumps changes as you adjust the speed your finger moves. Unplug from mains, and the surface becomes smooth. As the answer notes, this only happens when using the two-prong adapter without earthing. It also seems to be more noti…

My macbook was stolen years ago, but I remember it doing this exact thing. I never really looked it up or thought about it until now. It is a totally weird feeling for sure.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#53

Post by cs2818 »

I sometimes run into an interesting variation of this kind of problem. I often work with a Microsoft Surface tablet laying in front of my MacBook Pro, with my arms stretched over the tablet to type at times.

If the Surface is plugged in (no ground pin) and the MacBook Pro is also plugged in (ground pin), and my arms touch both at the same time, I can feel a tingling that quickly becomes unpleasant. Unplugging one or the other seems to be a work around.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#54

Post by josefdlange »

forgettableuser wrote: post #45
josefdlange wrote: post #17

Ungrounded adapter + bad mains power = zap! Ungrounded adapter + clean mains power = probably no zap Grounded adapter + bad mains power = probably no zap Grounded adapter + clean mains power = no zap It's not just the adapter and it's not just the mains power; it's when both come together. Electricity follows pretty simple rules when it comes down to it. Always always always ground your A/C connections. Why wouldn't…

I knew a guy in college who rented a house that didn't have any outlets with a ground plug. This became such a problem, he made his own ground by using a big metal pipe outside the house that was already deep in the earth, and running a wire from it to where he kept all his equipment. Then he used stuff like in that picture to make sure he could ground all his equipment.

This is the right way to use those! It's so rare to hear of proper usage.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#55

Post by josefdlange »

Hasz wrote: post #37
josefdlange wrote: post #17

Ungrounded adapter + bad mains power = zap! Ungrounded adapter + clean mains power = probably no zap Grounded adapter + bad mains power = probably no zap Grounded adapter + clean mains power = no zap It's not just the adapter and it's not just the mains power; it's when both come together. Electricity follows pretty simple rules when it comes down to it. Always always always ground your A/C connections. Why wouldn't…

Actually, for things with a non-conductive casing (think cheap nightlights, or those apple wall warts) there's no need for a ground. If anything, it's another part and more cost, thus it isn't included. In highly sensitive A/V systems, an isolation transformer is often used as well, neglecting a ground.

These are all better and more knowledgeable points than my own! I definitely only speak out of an abundance of caution having known people whose bad electricity and habits have damaged property.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#58

Post by hatsunearu »

Due to EMI reasons, for switching converters, the hot and neutral terminals of mains input is generally capacitively connected to the Earth prong via high frequency capacitors. That means if the earth prong isn't properly connected to actual earth, the earth prong now has your mains voltage divided by two on it. If the earth connection happens to be connected to the chassis, there's your shock.

It probably won't kill you unless you have a weak heart or if you're really unlucky because the EMI suppression caps are small enough to not supply lethal current, but can be really annoying.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#59

Post by hatsunearu »

josefdlange wrote: post #17

Ungrounded adapter + bad mains power = zap! Ungrounded adapter + clean mains power = probably no zap Grounded adapter + bad mains power = probably no zap Grounded adapter + clean mains power = no zap It's not just the adapter and it's not just the mains power; it's when both come together. Electricity follows pretty simple rules when it comes down to it. Always always always ground your A/C connections. Why wouldn't…

"clean" mains power has nothing to do with zapping. Where'd you hear this? I've literally never heard this nonsense before.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#60

Post by hatsunearu »

kosma wrote: post #34

For those of you who don't have access to proper grounding (because, for example, the wiring lacks PE or it's faulty): a plain separation transformer (1:1) between mains and your laptop might be able do the trick. Unfortunately if you have a larger setup (speakers, monitor, etc.) you have to connect everything to the separation transformer, otherwise you'll create leakage a path to mains some other way (say, through…

Yeah no, that won't work.
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