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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?

#61

Post by hatsunearu »

josefdlange wrote: post #21
Osmium wrote: post #19

FYI, I can't remember which way round it is, but only some of the UK 3-pronged adapters are actually earthed (as I discovered after having this problem myself). I think it's the extension cord that is properly earthed, whereas just the plug attachment that goes directly into the power brick is not. You can tell by looking up into the adapter (the part that plugs into the power brick) and seeing if it's metal or plast…

A certain vintage of Apple adapters have plastic posts where the ground would otherwise attach. This image is iPad 10W adapters, but the same follows for some older iBook/MacBook chargers: https://qph.ec.quoracdn.net/main-qimg-05fa7f5f0e6ce0dc43bf8c...

Double insulated appliances are fine, the circuit just needs to be designed with double insulation in mind.

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

#63

Post by xenadu02 »

kosma wrote: post #43
xenadu02 wrote: post #36

Earlier quoted context omitted.

> This is potentially deadly advice. A neutral/grounding fault will energize all your home devices with live potential; same with a live/neutral swap (unlikely but possible with Indian wiring standards). You are wrong. In the US the NEC requires this. If you bother to look inside your breaker panel you will find the neutral and ground wires are literally screwed down to the same bus bar. Any path your body (or the so…

> In the US the NEC requires this. If you bother to look inside your breaker panel you will find the neutral and ground wires are literally screwed down to the same bus bar. It could be different in US, but in modern European installations the PE and N bars are separate; older installations use common PEN; and even older ones don't even have PE. Each of the wiring schemes requires different approach and poses differe…

> It could be different in US, but in modern European installations the PE and N bars are separate

In the US a single PE+N wire feeds into the building. All building wiring is separated as in Europe. They are tied together in only one location, usually wherever the main switch is.

Just like Europe, really old installs in the US don't have ground (PE). Some are retrofitted with ground like my house in SF. One thing people should never do is connect neutral to ground at a secondary point. It can be tempting when you don't have access to run a ground wire but creates a serious potential for safety problems. The way to handle that is to install a GFCI (RCD) plug and put a sticker on it stating "No equipment ground" - the outlets actually come with those stickers for that purpose :)

As far as I know in European systems where the building has separate PE+N feeds they are still bonded together, it just happens at the transformer. I could be wrong about that though!

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

#64

Post by xenadu02 »

hatsunearu wrote: post #60
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.

Why not? Hospitals used to use isolating transformers for surgical electrical supply precisely to prevent any possibility of electrocuting patients.

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

#65

Post by closeparen »

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 discovered you can also switch the on and off by connecting and disconnecting your feet from ground.

Feet on the floor => shocks.

Feet on the beam of a wooden stool => no shocks.

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

#66

Post by derekp7 »

dogma1138 wrote: post #42
ganeshkrishnan wrote: post #29

Earlier quoted context omitted.

I had the same problem in Australia. I thought it was just me being over-sensitive to static electricity

You are probably connected to poorly grounded socket or a socket where hot and ground were switched. I had a grounding issue and I used to get shocked by my tower all the time, this is pretty common.

Same here, with some PCs back in a shop area. Come to find out, the outlets weren't getting a good ground due to painted conduit. And without a good ground, a cheap surge suppressor ended up dumping about 30 volts into the ground pin.

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

#67

Post by [deleted] »

xenadu02 wrote: post #63
kosma wrote: post #43

Earlier quoted context omitted.

> In the US the NEC requires this. If you bother to look inside your breaker panel you will find the neutral and ground wires are literally screwed down to the same bus bar. It could be different in US, but in modern European installations the PE and N bars are separate; older installations use common PEN; and even older ones don't even have PE. Each of the wiring schemes requires different approach and poses differe…

> It could be different in US, but in modern European installations the PE and N bars are separate In the US a single PE+N wire feeds into the building. All building wiring is separated as in Europe. They are tied together in only one location, usually wherever the main switch is. Just like Europe, really old installs in the US don't have ground (PE). Some are retrofitted with ground like my house in SF. One thing pe…

[deleted]

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

#68

Post by gh02t »

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.

You have to be careful with isolation transformers because there is one gotcha... the ground pin normally passes through to earth. I've witnessed someone blow up a nice $5000 Agilent oscilloscope before I could stop them because they didn't understand how to use an IT and plugged the scope into it so they could probe AC. Bad news, you're supposed to plug your test device into the IT not the scope because the BNC connectors in almost all oscilloscopes are connected straight through to the earth pin.

I heard "POW" from across the lab as soon as he clipped the probe on and knew I should have warned him. Nobody was hurt apart from our lab budget.

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

#69

Post by x0x0 »

hinkley wrote: post #12
x0x0 wrote: post #5

Earlier quoted context omitted.

There's also a good chance that, at least in part due to Apple's greed and extravagant prices for chargers / fragile power cords, many people are using knockoff chargers and don't know it. See also Amazon happily selling knockoffs as real -- Apple claims 90% of chargers it recently bought on Amazon are fake and is suing the supplier, though unfortunately is not suing Amazon [1], which might help Amazon find the will…

Have you seen a tear down of the authentic chargers? There's a lot going on in there.

As mentioned below, a reasonable estimate of the cost is $30.

They could also sell replacement user swappable magsafe cords and defang many of the complaints. But then they couldn't effectively charge $90 for a replacement cord.

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