16 ms·

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

193 points by luu 10y ago

taneq 10y ago
I've run across this before - once I measured the shell of my MBP at 90 volts DC. If you don't have access to a 3-pin charger, you could always use a separate earthing setup, such as an antistatic mat: https://en.wikipedia.org/wiki/Antistatic_device#Antistatic_mat https://en.wikipedia.org/wiki/Antistatic_device#Antistatic_m...
- avn2109 10y ago
  90 volts above earth ground? Or relative to something else?
  - taneq 10y ago
    It was a long time ago, but iirc it was relative to the nearest available metal object, which I think was the metal frame of a desk. It wasn't a super rigorous test. :P
sfifs 10y ago
Don't use Macs but I'm surprised Apple apparently didn't give an earthed power adapter by default on a metal skin product. This seems like negligence. Now that I think about it, my iPad's the same when charging.
- x0x0 10y ago
  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 to stop people selling fakes. [1] https://9to5mac.com/2016/10/19/amazon-fake-apple-chargers-cables/ https://9to5mac.com/2016/10/19/amazon-fake-apple-chargers-ca...
  - hinkley 10y ago
    Have you seen a tear down of the authentic chargers? There's a lot going on in there.
    - disillusioned 10y ago
      Right, but even still, you don't think Apple's commanding actual profit from them? They're up to $90...
      - forgettableuser 10y ago
        This was a really good teardown. http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html http://www.righto.com/2015/11/macbook-charger-teardown-surpr... The author also does consider the cost of the components.
    - x0x0 10y ago
      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.
      - hinkley 10y ago
        I have wanted that cord to be replaceable forever. At least it finally is now. Given how many the kids and dog destroy I consider it an improvement. I have wondered if the degradation of the cord wasn't some sort of safety guarantee rather than planned obsolescence. When the cord wears out you buy a new one instead of using the ancient one from eight years ago.
- an_account 10y ago
  They do give one by default, but you can disconnect it if you so choose. FWIW, I have never had a problem using the two pronged plug in the US. It's interesting to see all this preexisting problems with MacBooks surfacing after the recent release of the MBP
  - nunofgs 10y ago
    They don't include them anymore in the 2016 MacBooks
  - ClassyJacket 10y ago
    They stopped as of the new MacBooks this month :/
    - Keverw 10y ago
      Wow. More expensive and includes less... I don't know what they are thinking... I never even though of Mac's shocking people under normal use. wow.
- stillworks 10y ago
  In the U.K. they come with earthed plug. However I still noticed "buzzing" in the MBP, MBA and even iPad when I would touched them. Took the MBP in to the store. It didn't buzz there. They gave me a new power supply anyways and recommended I connect the plug directly into the wall socket. Turned out that the power strip I was using is not grounded even though it has three pin sockets ! When I plug Apple devices directly into the wall socket I don't notice any "buzzing". So now I don't connect the Apple devices via a power strip.
  - nicky0 10y ago
    Throw away that power strip.
    - mnw21cam 10y ago
      As in, right now. It violates every electric safety law around.
    - elcct 10y ago
      I would rather at least try to disassemble it before throwing away - otherwise it is likely that someone will pull it from the bin and use it or sell it.
  - rogual 10y ago
    My UK MacBook came with two plugs; one with a long cable and an earth connection, and one "short" one that's just the plug head, with no earth connection (the slot that the earth ring from the transformer connects to is just plastic inside). I get the shocks when using the short connector, and always have. Here is a DIY guide by someone who figured out how to fix the issue (danger, electricity, don't kill yourself) http://garethhayes.net/apple-power-plug-not-earthed/ http://garethhayes.net/apple-power-plug-not-earthed/
arikrak 10y ago
I never had that issue in the US (even when using a two-holed outlet), but I had that problem when I was visiting Israel. So it seems to only be an issue when using 220 volts and not a proper ground connection.
- mbreedlove 10y ago
  Same here. I've only had the issue in Thailand. No shocks at all in the US.
- WayneBro 10y ago
  I have this problem every winter. With my Macbbok it was the worst, it even caused the trackpad to stop functioning once, but it has also happened to some of my other devices as well. It's happened so often to me that I've trained myself to touch something to discharge the static before touching my equipment.
- burger_moon 10y ago
  I get it in my apartment (I live in the U.S.) which is brand new with 3 prong sockets if I have my feet on the ground (concrete floor) while roughing the laptop. I've experienced it a few more times at different peoples houses as well.
  - xenadu02 10y ago
    You might buy an outlet tester and see if your hot/neutral are reversed or if ground isn't connected. If it all checks out you can use a multimeter* to check potential between neutral and ground. If your apartment is wired correctly there should be almost no voltage between the two. At the breaker box the neutral and ground are supposed to be bonded together. That means only minor induced charges inside the building wiring would show up between the two. If there is any significant voltage then something is leaking on one of the lines or ground might not be bonded... it could even be floating if they didn't bother driving the grounding stake deep enough and the soil dried out a bit.
    - mnw21cam 10y ago
algesten 10y ago
I have this problem in India. I suspected the mains was dodgy, because during the many power outages i never got the shocks when on UPS. I got a multimeter and measured. The neutral was 70V and the phase 300ish. So the difference was roughly 230V but a switched power adapter would make this hover around 70 too (I believe an old coil based would probably been fine). The Indian electrician didn't understand my problem because his only tool was a regular bulb with two exposed wires that he jammed into the socket. "Look sir, light, power working" sigh.
- ars 10y ago
  The 70v is probably induced voltage at milliamp levels. You can fix it by bonding the neutral to ground at the breaker box.
  - kosma 10y ago
    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).
    - xenadu02 10y ago
      > 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 soil outside) can provide back to the generator pales in comparison to the neutral tap provided by the transformer. Grounding to dirt is about static electrical discharge, not the voltage provided by the generating station. The safety of providing a grounding wire is that metal parts of appliances must be connected to that ground. The ground wire itself is both bonded to neutral and connected to a metal grounding rod driven into the dirt. If any part of the appliance's internal works becomes energized and touches the metal casing the direct path to ground is designed to create a short circuit and trip the breaker immediately, rather than sitting there waiting for a human to come along and complete the circuit. If ground weren't bonded and the ground dried out or the grounding rod weren't properly installed then the scenario you describe would occur. A single faulty appliance would back-feed voltage onto every grounded appliance in the building. So in fact bonding is what creates safety, not the other way around.
Gracana 10y ago
My toughbook does this as well. One of the replies there says thinkpads have the same problem, and I have an IBM power adapter, so that could be the culprit. IIRC it's high frequency, so probably created by the supply itself rather than a floating neutral in the building wiring.
kosma 10y ago
My understanding is that it's caused by Y capacitors in the power supply's EMI filter leaking minimal amounts of current onto the case. As others have mentioned, proper grounding usually fixes the issue - although in one case I had to rewire an entire apartment because someone had a very lopsided idea what the PE wire is for. It was for a friend with a metal Macbook Pro, an exceptionally sensitive skin, and way too much time & money on their hands. :D The usual word of caution: I'm trained in electrical installations. A layperson - even one skilled with a multimeter and a soldering iron - should never attempt to modify ground connections or power distribution. There are dozens of potential (and very deadly) failure modes that require proper training to recognize and prevent.
- patcheudor 10y ago
  I have a mid 2015 13" MacBook Pro and I've measured up to 48v off the chassis between ground on properly wired circuits. I began investigating this after getting mild shocks after working out (sweaty) and while working on the MacBook in my lap while working on a PC laptop on my desk which also has an aluminum chassis. I tried an isolation transformer and the issue disappeared. I contacted Apple about it but crickets. I then did some current measurements and it was very low and of no concern at that voltage so I decided not to push the issue. As other have said, the solution is to use the three pronged cord that came with the power brick. You can feel this effect for yourself by using the two pronged plug and finding something grounded to the chassis to touch. With one hand, hold the grounded item while moving the palm of your other hand around the backside of the led. It's a bit dependent on the conductivity of your hands but I've found most people can feel it, even my dad who's a farmer and has very dry hands. Remember, if you get electrocuted, it's not my fault, it's Apple's. They have much deeper pockets than me.
edpichler 10y ago
I thought I was the only person to get shocks of my Macbook Pro, and that it had some problem. All because of the lack of a third pin.
josefdlange 10y ago
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 you? Also, never use one of these unless you've attached the little wire/alligator terminal to a ground somewhere: http://www.prestonelectronics.com/audio2/ttip/images/gndadapter.jpg http://www.prestonelectronics.com/audio2/ttip/images/gndadap...
- DanBC 10y ago
  I got the zaps. I live in the Uk where we have good quality mains power, and my mains power and all the sockets are tested once a year.
- Hasz 10y ago
  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.
  - josefdlange 10y ago
    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.
  - gh02t 10y ago
    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.
jordwest 10y ago
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 noticeable when connected to older buildings.
- pmoriarty 10y ago
  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.
  - bschwindHN 10y ago
    > and scary to think that two-prong outlets and appliances are legal anywhere In Japan, two prong outlets make up the vast majority of sockets, it kinda sucks.
    - kalleboo 10y ago
      I don't think I've ever seen a three-prong outlet in Japan (maybe only new installations?), but "earth screws" are quite common (any room prepared for an air conditioner will have one at least) http://www.hakusui-trading.co.jp/safety/img/img02.jpg http://www.hakusui-trading.co.jp/safety/img/img02.jpg
      - Teever 10y ago
        What? That's crazy looking! Why not just put the third prong in there if it's wired up to handle a screw? What's the point?
Osmium 10y ago
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 plastic...
- josefdlange 10y ago
  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-05fa7f5f0e6ce0dc43bf8c4124459cae?convert_to_webp=true https://qph.ec.quoracdn.net/main-qimg-05fa7f5f0e6ce0dc43bf8c...
  - hatsunearu 10y ago
    Double insulated appliances are fine, the circuit just needs to be designed with double insulation in mind.
- ponyfleisch 10y ago
  Yes, i had that problem. I used this workaround to fix it: http://imgur.com/a/cNzXx http://imgur.com/a/cNzXx
Osmium 10y ago
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 plastic...
deleted 10y ago
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kosma 10y ago
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 the audio jack). Caveat emptor: If you decide to go that route, make sure you can return the transformer if it doesn't to the job.
- hatsunearu 10y ago
  Yeah no, that won't work.
  - xenadu02 10y ago
    Why not? Hospitals used to use isolating transformers for surgical electrical supply precisely to prevent any possibility of electrocuting patients.
ah- 10y ago
I had the same happen to me while using a cheap ebay charger. Never happened with a genuine one. There's an interesting post about the internals: http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html http://www.righto.com/2015/11/macbook-charger-teardown-surpr...
Arathorn 10y ago
I've had this on every metal-chassis Mac I've ever owned. The chassis typically floats around 50V AC at 50Hz (in the UK, at least) - making it noticeably vibrate and tingle when you touch it, especially with the palm of your hands when typing. It also seems to make RSI worse. The solution, as everyone's pointed out, is to ensure you are correctly grounded.
chiph 10y ago
Test the outlet for proper wiring. If you're in the US, buy one of these: (there are similar models for use in other countries) https://www.amazon.com/Sperry-Instruments-GFI6302-Outlet-Tester/dp/B000RUL2UU https://www.amazon.com/Sperry-Instruments-GFI6302-Outlet-Tes... If this says good (two amber lights) and you're still getting shocked, follow up with a voltmeter and/or qualified electrician.
cyberferret 10y ago
Well, that explains it. Just last week my son was complaining that he was getting tiny shocks from the chassis of his Macbook. I thought he was just making excuses to not do his homework and told him to stop imagining it. Time to buy a 3 pin adapter!
scw 10y ago
My first summer job was doing IT for a small outfit, who worked out of an old house converted into an office. They had eight machines, all connected to a LaserJet printer via a parallel port switch. The parallel cables ran down into a crawlspace under the house, and it wasn't uncommon for one of the cables to work its way loose. No problem, tighten the parallel port connection at both ends, and you're back in business. But, being an old house, many outlets were missing ground pins. I must of electrocuted myself twenty times that summer.
cs2818 10y ago
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.
- SyneRyder 10y ago
  That solves an issue I've had as well, though it shows the MacBook Pro isn't really the fault. I have a Samsung TV (no ground-pin) and I would often watch it while using my MacBook Pro plugged in (ground pin). Because I didn't have wireless headphones yet I'd run a cable from the Samsung's headphone socket and plug my Bose headphones into that. If I was touching the MacBook case with one hand and grazed the metal parts of the 3.5" audio cable, I'd get quite a strong tingling & that almost becomes painful. Hadn't considered that the fault was the TV's lack of grounding.
anonu 10y ago
This happens to me regularly when I go back home (to a foreign country not the US). All the sockets have ground but the ground doesn't actually go anywhere... So you still get shocked. My solution was a bit lazier: plugin my MBP only when I'm not using it...
voltagex_ 10y ago
I'm assuming this is the same phenomenon with a metal-body camera I have - even though it was only charging off 5VDC at ~1A.
lifepillar 10y ago
Some time ago, Apple launched a recall program for defective power adapters: http://www.apple.com/support/ac-wallplug-adapter/ http://www.apple.com/support/ac-wallplug-adapter/ I had the problem mentioned in the subject. Replacing the plug adapter has fixed it.
londons_explore 10y ago
This problem is common. You can solve it by opening up the power supply and ripping out the bright blue Y capacitor inside. It looks like a slim M&M with 2 legs. Both apple official and 3rd party power supplies will have one. Do not damage the capacitor without removing it - that could lead to an electric shock. You can remove it by cutting it off with pliers or wire cutters. The power supply will work fine afterwards, but might emit a bit of radio interference, although generally not too much.
- derefr 10y ago
  > might emit a bit of radio interference, although generally not too much It might not cause the FCC to knock down your door, but what will it do to the laptop's own wireless and Bluetooth connectivity?
- cr3ative 10y ago
  Care to explain what this does?
hatsunearu 10y ago
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.
ksec 10y ago
So i am guessing the UK plug wont have this problem?
deleted 10y ago
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taitems 10y ago
I've had this on two MacBook Pros here in Australia. On the first one I took it in to a Genius Bar appointment and, while they acknowledged it happens to a "rare number of people", they basically said tough luck and to use the earthed power cable which is about 1.5m longer. By the second time I just accepted it as part of owning a MBP. As an aside, I should buy a lottery ticket given the number of rare issues that happen to my Apple products.
azsrz 10y ago
I had the same problem with the small plug. Using the extension cord with the ground solved it.
ti32x 10y ago
Also worth noting: some of the cheap knockoff magsafe adaptors available on ebay have an earthing "pin" inside the adaptor (the mushroom thing) which is actually just coated in a metallic coloured covering/paint. This doesn't actually provide contact to the existing ground pin, so you have this issue.
phee 10y ago
The point is, how did Apple manage to get away with it for all these years? why weren't they enforced to ship only the properly grounded adapter?
- creshal 10y ago
  Because the fanboys will suck up everything but a touch screen on their laptop.
- thrillgore 10y ago
  With a trotted meme/slogan like "You're holding it wrong" sorta explains it all does it not? I say this as a happy MacBook Air owner but i'm traveling soon and this had better not be an issue...
Animats 10y ago
Doesn't anybody have a DVM around? If you can feel a stray voltage, measure it, and find the source. As someone else pointed out, get an outlet tester.[1] They're about $7. You may have an open ground, or reversed hot/neutral. Once you've eliminated that, suspect the power supply. Make sure you have a UL-listed power supply. If you're getting stray AC voltage on the output side of a UL-listed supply, report it to UL. Here's the form.[2] There's no excuse for that. [1] https://www.amazon.com/Amprobe-ST-101B-Socket-Tester/dp/B008E07IEO https://www.amazon.com/Amprobe-ST-101B-Socket-Tester/dp/B008... [2] http://www.ul.com/customer-resources/market-surveillance-department/market-surveillance/ http://www.ul.com/customer-resources/market-surveillance-dep...
- phee 10y ago
  About reversed hot/neutral. We have these[1] symmetrical adapters in Europe. How are you supposed to know the proper orientation? You are not. Because you either have an earthed metal case or you have a double insulated device. My magsafe adapters have a "double insulation" symbol, a tiny tiny one near "UL Japan", but still need a earthed prong to not feel any shock from the laptop metal case. 1. http://images.apple.com/support/assets/images/products/ac-wall-adapter/eur_adapter.png http://images.apple.com/support/assets/images/products/ac-wa...
bitL 10y ago
I still remember some Dell Precision workstation having a "magic touchpad" as it reacted even when your fingers were an inch away - must have been a pretty powerful electromagnetic field! And the case was always giving shocks at random times.
chunkiestbacon 10y ago
Happened to me too with my 2011 macbook air and my 2010 macbok pro 15' when using the 2 prong adapter at home in Europe. Currently typing this on a 13'' late 2014 13'' MBP with 2 prongs in Japan. No problems.
snarfy 10y ago
I'm curious if this would trip a GFCI when you touched the lid. People often judge whether they will get shocked based on resistance, but humans are also capacitors. The casing of a macbook is a machined aluminum frame which will act as one plate in a capacitor. Your hand is the other plate. Unlike DC, AC passes through capacitors.
thrusong 10y ago
My iMac, specifically the USB keyboard (I needed the numpad), gives a slight electrical sensation when I touch it anywhere other than a key.
- misja111 10y ago
  I experienced the same with an aluminium Apple keyboard connected to a non-Apple PC; small electric shocks now and then when I touched the aluminium. I contacted Apple about it and they said it was impossible .. Luckily I had purchased the keyboard online and I could still return it.
amelius 10y ago
Could somebody draw a simple diagram with resistors and perhaps capacitors to illustrate what the problem is?
return0 10y ago
I would suspect it's a common problem with aluminum casings in general. They also have that cold feeling. IT's one of the reasons i prefer the matte plastic of thinkpads.
thrillgore 10y ago
Well this is just great. I'm traveling overseas to a country with 220v (South Korea) and I am concerned my Air will end up shocking me.
rando444 10y ago
I've noticed a similar problem. I have a macbook pro and a macbook air and whenever I have both of them plugged in and am touching both of them at the same time (usually one arm laying across both of them) I can feel where my arm is touching the laptops start to hurt/burn. I figured the electricity is now going through my body, but assumed it was a problem with the laptop, not necessarily the electricity.
BJBBB 10y ago
Geez peoples - so much misinformation. Touch current test methods and limits are well-defined through out the world. Poor power 'quality' may affect this measurement, but is not a significant contributor to the magnitude of potential leakage through the ground wire or through exposed metal surfaces. It is a function of the power conversion equipment connected to, or internal, to the device. Even where wiring does not meet code, the upper limit to this measurement is well defined per the simulated fault conditions required in the test methods. People that claim to be engineers need to read and understand the basic physics behind the product safety standards scoped by your equipment. For EU, code is defined in BS7671/IEC60364; and NFPA70 (mostly article 250) in the U.S.; and similar stuff in C22.1 for Canada. ITE power supplies must meet the locally harmonized version of IEC60950-1 (soon to be obsoleted by IEC62368-1). Where there is no ground pin, North American power supplies must meet UL1310/CSA No.223. These standards all have specific limits for voltage, current, and VA levels that can be exposed to the end-user, for both normal and abnormal operating conditions.
- phee 10y ago
  > Where there is no ground pin, North American power supplies must meet UL1310/CSA No.223 So, as far as I can tell, with a brief skim of the standard, a class 2 device should have no more than 0.5 mA leakage current, right? I just measured the leakage from my macbookpro through my body to ground and it's about 50 μA. Well within the limits. So I guess that's why they never did anything about it. Still amazing that you can clearly feel this current: if you lightly brush your wrist around the sharp edges it actually hurts. I wonder how 500 μA would feel.
  - BJBBB 10y ago
    Depends on the 'bandwidth' of the signal and the test equipment and the individual. Generally consider many non-medical measurements below 025mA suspect, as few design engineers make an effort to understand the various frequency components of the voltage and current leakage signals, and/or understand the effects to the signal of instrument impedances. Have had several discussions with Mr.Pete Perkins (he sits on several STCs and has written several IEEE papers) on this subject, and we agree that the human body model referenced by these safety standards being used for the measurement network (IEC60990) have problems because the medical community does not understand physics. As the various standards committees continue to look at the body of work being done by bioengineers, will probably see better measurement methods being codified. Human response and perception to electricity has significant variance and resultant effects/affects. My wife can detect less than 10uA at 200Hz/42V. My detection threshold is at least an order of magnitude greater, even at 50Hz.
gravypod 10y ago
If you can get a shock from this, and as someone else is saying that they can feel it when they wave their hand over the lid, then how is this passing any EMI screening? That's got to be noisier then an old ham radio.
captainmuon 10y ago
Maybe a stupid question, but why is the case grounded at all (I mean as in "put on a common zero potential", not as in "connected to earth")? I imagine it is convenient to use the case as common ground, but it seems wierd. Is is unavoidable production-wise?
nikolay 10y ago
I have the same issues when I'm in Bulgaria during the summer (220V, 50Hz), and always wondered how Apple did something so basic so terribly wrong!

193 points by luu 10y ago

taneq 10y ago

I've run across this before - once I measured the shell of my MBP at 90 volts DC. If you don't have access to a 3-pin charger, you could always use a separate earthing setup, such as an antistatic mat: https://en.wikipedia.org/wiki/Antistatic_device#Antistatic_mat https://en.wikipedia.org/wiki/Antistatic_device#Antistatic_m...

avn2109 10y ago
90 volts above earth ground? Or relative to something else?
- taneq 10y ago
  It was a long time ago, but iirc it was relative to the nearest available metal object, which I think was the metal frame of a desk. It wasn't a super rigorous test. :P

sfifs 10y ago

Don't use Macs but I'm surprised Apple apparently didn't give an earthed power adapter by default on a metal skin product. This seems like negligence. Now that I think about it, my iPad's the same when charging.

x0x0 10y ago
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 to stop people selling fakes. [1] https://9to5mac.com/2016/10/19/amazon-fake-apple-chargers-cables/ https://9to5mac.com/2016/10/19/amazon-fake-apple-chargers-ca...
- hinkley 10y ago
  Have you seen a tear down of the authentic chargers? There's a lot going on in there.
  - disillusioned 10y ago
    Right, but even still, you don't think Apple's commanding actual profit from them? They're up to $90...
    - forgettableuser 10y ago
      This was a really good teardown. http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html http://www.righto.com/2015/11/macbook-charger-teardown-surpr... The author also does consider the cost of the components.
  - x0x0 10y ago
    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.
    - hinkley 10y ago
      I have wanted that cord to be replaceable forever. At least it finally is now. Given how many the kids and dog destroy I consider it an improvement. I have wondered if the degradation of the cord wasn't some sort of safety guarantee rather than planned obsolescence. When the cord wears out you buy a new one instead of using the ancient one from eight years ago.
an_account 10y ago
They do give one by default, but you can disconnect it if you so choose. FWIW, I have never had a problem using the two pronged plug in the US. It's interesting to see all this preexisting problems with MacBooks surfacing after the recent release of the MBP
- nunofgs 10y ago
  They don't include them anymore in the 2016 MacBooks
- ClassyJacket 10y ago
  They stopped as of the new MacBooks this month :/
  - Keverw 10y ago
    Wow. More expensive and includes less... I don't know what they are thinking... I never even though of Mac's shocking people under normal use. wow.
stillworks 10y ago
In the U.K. they come with earthed plug. However I still noticed "buzzing" in the MBP, MBA and even iPad when I would touched them. Took the MBP in to the store. It didn't buzz there. They gave me a new power supply anyways and recommended I connect the plug directly into the wall socket. Turned out that the power strip I was using is not grounded even though it has three pin sockets ! When I plug Apple devices directly into the wall socket I don't notice any "buzzing". So now I don't connect the Apple devices via a power strip.
- nicky0 10y ago
  Throw away that power strip.
  - mnw21cam 10y ago
    As in, right now. It violates every electric safety law around.
  - elcct 10y ago
    I would rather at least try to disassemble it before throwing away - otherwise it is likely that someone will pull it from the bin and use it or sell it.
- rogual 10y ago
  My UK MacBook came with two plugs; one with a long cable and an earth connection, and one "short" one that's just the plug head, with no earth connection (the slot that the earth ring from the transformer connects to is just plastic inside). I get the shocks when using the short connector, and always have. Here is a DIY guide by someone who figured out how to fix the issue (danger, electricity, don't kill yourself) http://garethhayes.net/apple-power-plug-not-earthed/ http://garethhayes.net/apple-power-plug-not-earthed/

arikrak 10y ago

I never had that issue in the US (even when using a two-holed outlet), but I had that problem when I was visiting Israel. So it seems to only be an issue when using 220 volts and not a proper ground connection.

mbreedlove 10y ago
Same here. I've only had the issue in Thailand. No shocks at all in the US.
WayneBro 10y ago
I have this problem every winter. With my Macbbok it was the worst, it even caused the trackpad to stop functioning once, but it has also happened to some of my other devices as well. It's happened so often to me that I've trained myself to touch something to discharge the static before touching my equipment.
burger_moon 10y ago
I get it in my apartment (I live in the U.S.) which is brand new with 3 prong sockets if I have my feet on the ground (concrete floor) while roughing the laptop. I've experienced it a few more times at different peoples houses as well.
- xenadu02 10y ago
  You might buy an outlet tester and see if your hot/neutral are reversed or if ground isn't connected. If it all checks out you can use a multimeter* to check potential between neutral and ground. If your apartment is wired correctly there should be almost no voltage between the two. At the breaker box the neutral and ground are supposed to be bonded together. That means only minor induced charges inside the building wiring would show up between the two. If there is any significant voltage then something is leaking on one of the lines or ground might not be bonded... it could even be floating if they didn't bother driving the grounding stake deep enough and the soil dried out a bit.
  - mnw21cam 10y ago

algesten 10y ago

I have this problem in India. I suspected the mains was dodgy, because during the many power outages i never got the shocks when on UPS. I got a multimeter and measured. The neutral was 70V and the phase 300ish. So the difference was roughly 230V but a switched power adapter would make this hover around 70 too (I believe an old coil based would probably been fine). The Indian electrician didn't understand my problem because his only tool was a regular bulb with two exposed wires that he jammed into the socket. "Look sir, light, power working" sigh.

ars 10y ago
The 70v is probably induced voltage at milliamp levels. You can fix it by bonding the neutral to ground at the breaker box.
- kosma 10y ago
  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).
  - xenadu02 10y ago
    > 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 soil outside) can provide back to the generator pales in comparison to the neutral tap provided by the transformer. Grounding to dirt is about static electrical discharge, not the voltage provided by the generating station. The safety of providing a grounding wire is that metal parts of appliances must be connected to that ground. The ground wire itself is both bonded to neutral and connected to a metal grounding rod driven into the dirt. If any part of the appliance's internal works becomes energized and touches the metal casing the direct path to ground is designed to create a short circuit and trip the breaker immediately, rather than sitting there waiting for a human to come along and complete the circuit. If ground weren't bonded and the ground dried out or the grounding rod weren't properly installed then the scenario you describe would occur. A single faulty appliance would back-feed voltage onto every grounded appliance in the building. So in fact bonding is what creates safety, not the other way around.

Gracana 10y ago

My toughbook does this as well. One of the replies there says thinkpads have the same problem, and I have an IBM power adapter, so that could be the culprit. IIRC it's high frequency, so probably created by the supply itself rather than a floating neutral in the building wiring.

kosma 10y ago

My understanding is that it's caused by Y capacitors in the power supply's EMI filter leaking minimal amounts of current onto the case. As others have mentioned, proper grounding usually fixes the issue - although in one case I had to rewire an entire apartment because someone had a very lopsided idea what the PE wire is for. It was for a friend with a metal Macbook Pro, an exceptionally sensitive skin, and way too much time & money on their hands. :D The usual word of caution: I'm trained in electrical installations. A layperson - even one skilled with a multimeter and a soldering iron - should never attempt to modify ground connections or power distribution. There are dozens of potential (and very deadly) failure modes that require proper training to recognize and prevent.

patcheudor 10y ago
I have a mid 2015 13" MacBook Pro and I've measured up to 48v off the chassis between ground on properly wired circuits. I began investigating this after getting mild shocks after working out (sweaty) and while working on the MacBook in my lap while working on a PC laptop on my desk which also has an aluminum chassis. I tried an isolation transformer and the issue disappeared. I contacted Apple about it but crickets. I then did some current measurements and it was very low and of no concern at that voltage so I decided not to push the issue. As other have said, the solution is to use the three pronged cord that came with the power brick. You can feel this effect for yourself by using the two pronged plug and finding something grounded to the chassis to touch. With one hand, hold the grounded item while moving the palm of your other hand around the backside of the led. It's a bit dependent on the conductivity of your hands but I've found most people can feel it, even my dad who's a farmer and has very dry hands. Remember, if you get electrocuted, it's not my fault, it's Apple's. They have much deeper pockets than me.

edpichler 10y ago

I thought I was the only person to get shocks of my Macbook Pro, and that it had some problem. All because of the lack of a third pin.

josefdlange 10y ago

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 you? Also, never use one of these unless you've attached the little wire/alligator terminal to a ground somewhere: http://www.prestonelectronics.com/audio2/ttip/images/gndadapter.jpg http://www.prestonelectronics.com/audio2/ttip/images/gndadap...

DanBC 10y ago
I got the zaps. I live in the Uk where we have good quality mains power, and my mains power and all the sockets are tested once a year.
Hasz 10y ago
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.
- josefdlange 10y ago
  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.
- gh02t 10y ago
  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.

jordwest 10y ago

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 noticeable when connected to older buildings.

pmoriarty 10y ago
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.
- bschwindHN 10y ago
  > and scary to think that two-prong outlets and appliances are legal anywhere In Japan, two prong outlets make up the vast majority of sockets, it kinda sucks.
  - kalleboo 10y ago
    I don't think I've ever seen a three-prong outlet in Japan (maybe only new installations?), but "earth screws" are quite common (any room prepared for an air conditioner will have one at least) http://www.hakusui-trading.co.jp/safety/img/img02.jpg http://www.hakusui-trading.co.jp/safety/img/img02.jpg
    - Teever 10y ago
      What? That's crazy looking! Why not just put the third prong in there if it's wired up to handle a screw? What's the point?

Osmium 10y ago

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 plastic...

josefdlange 10y ago
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-05fa7f5f0e6ce0dc43bf8c4124459cae?convert_to_webp=true https://qph.ec.quoracdn.net/main-qimg-05fa7f5f0e6ce0dc43bf8c...
- hatsunearu 10y ago
  Double insulated appliances are fine, the circuit just needs to be designed with double insulation in mind.
ponyfleisch 10y ago
Yes, i had that problem. I used this workaround to fix it: http://imgur.com/a/cNzXx http://imgur.com/a/cNzXx

Osmium 10y ago

deleted 10y ago

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kosma 10y ago

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 the audio jack). Caveat emptor: If you decide to go that route, make sure you can return the transformer if it doesn't to the job.

hatsunearu 10y ago
Yeah no, that won't work.
- xenadu02 10y ago
  Why not? Hospitals used to use isolating transformers for surgical electrical supply precisely to prevent any possibility of electrocuting patients.

ah- 10y ago

I had the same happen to me while using a cheap ebay charger. Never happened with a genuine one. There's an interesting post about the internals: http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html http://www.righto.com/2015/11/macbook-charger-teardown-surpr...

Arathorn 10y ago

I've had this on every metal-chassis Mac I've ever owned. The chassis typically floats around 50V AC at 50Hz (in the UK, at least) - making it noticeably vibrate and tingle when you touch it, especially with the palm of your hands when typing. It also seems to make RSI worse. The solution, as everyone's pointed out, is to ensure you are correctly grounded.

chiph 10y ago

Test the outlet for proper wiring. If you're in the US, buy one of these: (there are similar models for use in other countries) https://www.amazon.com/Sperry-Instruments-GFI6302-Outlet-Tester/dp/B000RUL2UU https://www.amazon.com/Sperry-Instruments-GFI6302-Outlet-Tes... If this says good (two amber lights) and you're still getting shocked, follow up with a voltmeter and/or qualified electrician.

cyberferret 10y ago

Well, that explains it. Just last week my son was complaining that he was getting tiny shocks from the chassis of his Macbook. I thought he was just making excuses to not do his homework and told him to stop imagining it. Time to buy a 3 pin adapter!

scw 10y ago

My first summer job was doing IT for a small outfit, who worked out of an old house converted into an office. They had eight machines, all connected to a LaserJet printer via a parallel port switch. The parallel cables ran down into a crawlspace under the house, and it wasn't uncommon for one of the cables to work its way loose. No problem, tighten the parallel port connection at both ends, and you're back in business. But, being an old house, many outlets were missing ground pins. I must of electrocuted myself twenty times that summer.

cs2818 10y ago

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.

SyneRyder 10y ago
That solves an issue I've had as well, though it shows the MacBook Pro isn't really the fault. I have a Samsung TV (no ground-pin) and I would often watch it while using my MacBook Pro plugged in (ground pin). Because I didn't have wireless headphones yet I'd run a cable from the Samsung's headphone socket and plug my Bose headphones into that. If I was touching the MacBook case with one hand and grazed the metal parts of the 3.5" audio cable, I'd get quite a strong tingling & that almost becomes painful. Hadn't considered that the fault was the TV's lack of grounding.

anonu 10y ago

This happens to me regularly when I go back home (to a foreign country not the US). All the sockets have ground but the ground doesn't actually go anywhere... So you still get shocked. My solution was a bit lazier: plugin my MBP only when I'm not using it...

voltagex_ 10y ago

I'm assuming this is the same phenomenon with a metal-body camera I have - even though it was only charging off 5VDC at ~1A.

lifepillar 10y ago

Some time ago, Apple launched a recall program for defective power adapters: http://www.apple.com/support/ac-wallplug-adapter/ http://www.apple.com/support/ac-wallplug-adapter/ I had the problem mentioned in the subject. Replacing the plug adapter has fixed it.

londons_explore 10y ago

This problem is common. You can solve it by opening up the power supply and ripping out the bright blue Y capacitor inside. It looks like a slim M&M with 2 legs. Both apple official and 3rd party power supplies will have one. Do not damage the capacitor without removing it - that could lead to an electric shock. You can remove it by cutting it off with pliers or wire cutters. The power supply will work fine afterwards, but might emit a bit of radio interference, although generally not too much.

derefr 10y ago
> might emit a bit of radio interference, although generally not too much It might not cause the FCC to knock down your door, but what will it do to the laptop's own wireless and Bluetooth connectivity?
cr3ative 10y ago
Care to explain what this does?

hatsunearu 10y ago

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.

ksec 10y ago

So i am guessing the UK plug wont have this problem?

deleted 10y ago

[deleted]

taitems 10y ago

I've had this on two MacBook Pros here in Australia. On the first one I took it in to a Genius Bar appointment and, while they acknowledged it happens to a "rare number of people", they basically said tough luck and to use the earthed power cable which is about 1.5m longer. By the second time I just accepted it as part of owning a MBP. As an aside, I should buy a lottery ticket given the number of rare issues that happen to my Apple products.

azsrz 10y ago

I had the same problem with the small plug. Using the extension cord with the ground solved it.

ti32x 10y ago

Also worth noting: some of the cheap knockoff magsafe adaptors available on ebay have an earthing "pin" inside the adaptor (the mushroom thing) which is actually just coated in a metallic coloured covering/paint. This doesn't actually provide contact to the existing ground pin, so you have this issue.

phee 10y ago

The point is, how did Apple manage to get away with it for all these years? why weren't they enforced to ship only the properly grounded adapter?

creshal 10y ago
Because the fanboys will suck up everything but a touch screen on their laptop.
thrillgore 10y ago
With a trotted meme/slogan like "You're holding it wrong" sorta explains it all does it not? I say this as a happy MacBook Air owner but i'm traveling soon and this had better not be an issue...

Animats 10y ago

Doesn't anybody have a DVM around? If you can feel a stray voltage, measure it, and find the source. As someone else pointed out, get an outlet tester.[1] They're about $7. You may have an open ground, or reversed hot/neutral. Once you've eliminated that, suspect the power supply. Make sure you have a UL-listed power supply. If you're getting stray AC voltage on the output side of a UL-listed supply, report it to UL. Here's the form.[2] There's no excuse for that. [1] https://www.amazon.com/Amprobe-ST-101B-Socket-Tester/dp/B008E07IEO https://www.amazon.com/Amprobe-ST-101B-Socket-Tester/dp/B008... [2] http://www.ul.com/customer-resources/market-surveillance-department/market-surveillance/ http://www.ul.com/customer-resources/market-surveillance-dep...

phee 10y ago
About reversed hot/neutral. We have these[1] symmetrical adapters in Europe. How are you supposed to know the proper orientation? You are not. Because you either have an earthed metal case or you have a double insulated device. My magsafe adapters have a "double insulation" symbol, a tiny tiny one near "UL Japan", but still need a earthed prong to not feel any shock from the laptop metal case. 1. http://images.apple.com/support/assets/images/products/ac-wall-adapter/eur_adapter.png http://images.apple.com/support/assets/images/products/ac-wa...

bitL 10y ago

I still remember some Dell Precision workstation having a "magic touchpad" as it reacted even when your fingers were an inch away - must have been a pretty powerful electromagnetic field! And the case was always giving shocks at random times.

chunkiestbacon 10y ago

Happened to me too with my 2011 macbook air and my 2010 macbok pro 15' when using the 2 prong adapter at home in Europe. Currently typing this on a 13'' late 2014 13'' MBP with 2 prongs in Japan. No problems.

snarfy 10y ago

I'm curious if this would trip a GFCI when you touched the lid. People often judge whether they will get shocked based on resistance, but humans are also capacitors. The casing of a macbook is a machined aluminum frame which will act as one plate in a capacitor. Your hand is the other plate. Unlike DC, AC passes through capacitors.

thrusong 10y ago

My iMac, specifically the USB keyboard (I needed the numpad), gives a slight electrical sensation when I touch it anywhere other than a key.

misja111 10y ago
I experienced the same with an aluminium Apple keyboard connected to a non-Apple PC; small electric shocks now and then when I touched the aluminium. I contacted Apple about it and they said it was impossible .. Luckily I had purchased the keyboard online and I could still return it.

amelius 10y ago

Could somebody draw a simple diagram with resistors and perhaps capacitors to illustrate what the problem is?

return0 10y ago

I would suspect it's a common problem with aluminum casings in general. They also have that cold feeling. IT's one of the reasons i prefer the matte plastic of thinkpads.

thrillgore 10y ago

Well this is just great. I'm traveling overseas to a country with 220v (South Korea) and I am concerned my Air will end up shocking me.

rando444 10y ago

I've noticed a similar problem. I have a macbook pro and a macbook air and whenever I have both of them plugged in and am touching both of them at the same time (usually one arm laying across both of them) I can feel where my arm is touching the laptops start to hurt/burn. I figured the electricity is now going through my body, but assumed it was a problem with the laptop, not necessarily the electricity.

BJBBB 10y ago

Geez peoples - so much misinformation. Touch current test methods and limits are well-defined through out the world. Poor power 'quality' may affect this measurement, but is not a significant contributor to the magnitude of potential leakage through the ground wire or through exposed metal surfaces. It is a function of the power conversion equipment connected to, or internal, to the device. Even where wiring does not meet code, the upper limit to this measurement is well defined per the simulated fault conditions required in the test methods. People that claim to be engineers need to read and understand the basic physics behind the product safety standards scoped by your equipment. For EU, code is defined in BS7671/IEC60364; and NFPA70 (mostly article 250) in the U.S.; and similar stuff in C22.1 for Canada. ITE power supplies must meet the locally harmonized version of IEC60950-1 (soon to be obsoleted by IEC62368-1). Where there is no ground pin, North American power supplies must meet UL1310/CSA No.223. These standards all have specific limits for voltage, current, and VA levels that can be exposed to the end-user, for both normal and abnormal operating conditions.

phee 10y ago
> Where there is no ground pin, North American power supplies must meet UL1310/CSA No.223 So, as far as I can tell, with a brief skim of the standard, a class 2 device should have no more than 0.5 mA leakage current, right? I just measured the leakage from my macbookpro through my body to ground and it's about 50 μA. Well within the limits. So I guess that's why they never did anything about it. Still amazing that you can clearly feel this current: if you lightly brush your wrist around the sharp edges it actually hurts. I wonder how 500 μA would feel.
- BJBBB 10y ago
  Depends on the 'bandwidth' of the signal and the test equipment and the individual. Generally consider many non-medical measurements below 025mA suspect, as few design engineers make an effort to understand the various frequency components of the voltage and current leakage signals, and/or understand the effects to the signal of instrument impedances. Have had several discussions with Mr.Pete Perkins (he sits on several STCs and has written several IEEE papers) on this subject, and we agree that the human body model referenced by these safety standards being used for the measurement network (IEC60990) have problems because the medical community does not understand physics. As the various standards committees continue to look at the body of work being done by bioengineers, will probably see better measurement methods being codified. Human response and perception to electricity has significant variance and resultant effects/affects. My wife can detect less than 10uA at 200Hz/42V. My detection threshold is at least an order of magnitude greater, even at 50Hz.

gravypod 10y ago

If you can get a shock from this, and as someone else is saying that they can feel it when they wave their hand over the lid, then how is this passing any EMI screening? That's got to be noisier then an old ham radio.

captainmuon 10y ago

Maybe a stupid question, but why is the case grounded at all (I mean as in "put on a common zero potential", not as in "connected to earth")? I imagine it is convenient to use the case as common ground, but it seems wierd. Is is unavoidable production-wise?

nikolay 10y ago

I have the same issues when I'm in Bulgaria during the summer (220V, 50Hz), and always wondered how Apple did something so basic so terribly wrong!