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.
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.
In Japan, two prong outlets make up the vast majority of sockets, it kinda sucks.
What's the point?
I think it's just a legacy thing - historically, the only things that needed grounding were static appliances like fridges, washing machines and air conditioners. The manual in our fridge has this instruction for earthing http://mayoyo.tokyo/jIe.jpg
I need to revise my comment that "I don't think I've ever seen a three-prong outlet in Japan", because now that I have power sockets on my mind, I just saw a three-prong outlet at my gym. So I guess newer buildings have them.
You can also die if you stick your finger for a long time (24H) in a small current.
TeslaTouch: Electrovibration for Touch Surfaces:
Question: aren't laptops powered off DC (there's a rectifier/transformer combo in the power brick) so how would AC get to the case of the laptop?
However, the voltage measured from either pin to ground might very well fluctuate. Without the grounding pin on the power supply, the DC side of the supply may 'float' with respect to earth ground. If you plot the voltages measured from each pin to ground, it probably looks like a pair of sine waves, one shifted 20 volts above the other.
This is a common problem, the power cable from the power adapter to your laptop is also usually connected to ground, if the ground is hot then you get shocked.
Bring back transformers! (ok, don't, but...)
Feet on the floor => shocks.
Feet on the beam of a wooden stool => no shocks.
Users enjoying electric shocks. Reality distortion field operating at nominal.
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"
This vacuum had the most five-star reviews on Amazon, but then a minority of people started complaining and leaving one-star reviews, saying they were getting shocked.
The reactions from the fanboy crowd were non-sympathetic ("you're imagining it," "it's just static," etc.), and they mass downvoted every one-star review. Some of the people claimed they were getting shocked PRETTY HARD, too, as in it knocked them over. IIRC, even Shark responded saying that it was impossible for the vacuum to shock you.
I remember seeing this while looking at vacuums for my elderly mother who has a heart condition. To the electrical engineer in me, everything made sense!
I started defending every single one-star reviewer person, and I wrote my own very detailed review with photos of the handle. Soon, the tide turned, and more people started upvoting my review than downvoting it; and I even received personal "thank you" messages from the people who got shocked ("finally someone believes me").
It eventually got to the point where a year later in 2014, Shark released an updated model with no more metal strip. Seeing this, I bought the new model for my mother. I'd like to think I can give myself SOME credit for causing them to do that.
Not only that, the upvotes from that alone were a good part of the reason I became an Amazon Top Reviewer.
And later released a workaround to make the hardware work in a slower, more power consuming backwards compatibility mode so Intel can continue not properly supporting the hardware in Linux.
But sure, it was totally "Lenovo blocking Linux".
Lenovo initially released a BIOS with a goto statement added to jmp out of the disk controller mode setting (which is normally present and allows the user to change back to AHCI mode). Reverse engineers on the Lenovo forums discovered this modification while studying the disassembly.
Then, one user patched the BIOS and manually reflashed it using an SPI flasher and some soldering, and Linux worked just fine by detecting the drive.
Yes, the ideal solution is that Intel gives specs to OSS devs to build a driver (or even builds on themselves), but the path of least resistance is to have Lenovo unblock that BIOS setting, which amounts to changing one line of code, or 15 minutes of one engineer's time.
Because switching to AHCI mode with Windows installed would brick the machine (Yay, Microsoft), and Lenovo foolishly assumed that people who wanted to use Linux would buy one of the Linux certified machines instead (X1 Yoga and 60 series Yoga devices are all certified: https://support.lenovo.com/us/en/documents/pd031426 – but I'm sure that's just more proof that Lenovo hates Linux for some reason).
> the path of least resistance is to have Lenovo unblock that BIOS setting, which amounts to changing one line of code, or 15 minutes of one engineer's time.
Which is exactly what Lenovo did: https://forums.lenovo.com/t5/Lenovo-Yoga-Series-Notebooks/Yo...
There are tons of BIOS settings that could "brick" my machine though, it's a weak argument, really. My car didn't come with a lock on the hood.
"Which is exactly what Lenovo did"
Okay, you're acting like it didn't require any teeth pulling on our end to get them to release it (check out the 30+ page forum topics).
The hot water pipes were being used as the earth, and the electricity could leap across the pipe in bad weather.
I had a grounding issue and I used to get shocked by my tower all the time, this is pretty common.
It's the devices responsibility to design for that.
You can fix it by bonding the neutral to ground at the breaker box.
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.
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 different hazards. There's no single recipe that would work on all of them.
My bottom line is: don't make arbitrary connections in the breaker box without proper knowledge and training; and don't give random electrical advice on the internet without knowledge of local codes.
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!
For example in the UK neutral is traditionally grounded at the electrical substation, which serves several hundred homes, and all lines are separate / unbonded within the house.
In the most recent PME standard in the UK the earth and neutral are bonded back to the substation as the Protected Earthed Neutral but that is achieved on the supply-side, not the in consumer equipment.
OP's very first sentence clearly stated they are in India, where this is obviously dangerous advice because most devices (and piping) connect their surfaces to Earth, which is new Neutral.
Earth here was a metal rod into the ground, and I only found out much later they fixed the RCD issue by disconnecting the rod and I started getting electric shocks from touching my fridge while my crappy toaster was connected.
That's when I decided to not mess with electrics in India. It's dangerous enough as it is.
As for the 70V, I eventually managed to reach someone in the electrics company that understood my issue, and they told me a local transformer for the whole street was broken. And they didn't have any plan to fix it.
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.
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.
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:
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.
In highly sensitive A/V systems, an isolation transformer is often used as well, neglecting a ground.
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.
I know this video is supposed to be funny, but I couldn't bring myself to laugh. Too many people die making the same mistakes.
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.
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.
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.
Class 2 (arabic numeral) is for limited power sources, regardless of construction class.
Class II (roman numeral) indicates a construction class where safety cannot be dependent on a ground bond.
Class I (roman numeral) indicates safety is dependent on a reliable ground bound.
Class I equipment, depending on the scoped end-use equipment safety standard, can have up to 25mA of leakage.
Class II equipment, depending on the end-use environment, can be limited to 0.25mA of available touch leakage.
A good reference for Class 2 and 3 equipment is the UL5085-x series (same as CSA No66.x).
For the EU, there are no harmonized standards in the Low Voltage Directive that have an equivalent Class 2/3 construction, although there are several safety standards that address requirements for 'inherently limited' power sources.
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.
The solution, as everyone's pointed out, is to ensure you are correctly grounded.
As someone else pointed out, get an outlet tester. 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. There's no excuse for that.
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.
If this says good (two amber lights) and you're still getting shocked, follow up with a voltmeter and/or qualified electrician.
Now that I think about it, my iPad's the same when charging.
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.
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)
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
The author also does consider the cost of the components.
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.
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.
I've experienced it a few more times at different peoples houses as well.
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.
Note this advice is country-specific. In some countries, the bonding is done further away from the house.
In any case, you should never trust the neutral line to be an earth. If a fault occurs that disconnects the neutral line from the supply, your neutral line will have deadly voltage on it by virtue of being connected to live through your appliances. Moreover, depending on the multimeter you use, if you measure the voltage between neutral and earth, you could possibly trip the RCD in the distribution unit (if you have one).
The rules are simple in most countries - if it has any touchable metal parts, it must be earthed.
Reading jordwest's 60Hz comment, it seems to do with grounding. So do MBPs and iPhones purchased in Europe still experience this issue if the apartment isn't grounded properly?
It's happened so often to me that I've trained myself to touch something to discharge the static before touching my equipment.
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.
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...
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_m...
There's an interesting post about the internals: http://www.righto.com/2015/11/macbook-charger-teardown-surpr...
I had the problem mentioned in the subject. Replacing the plug adapter has fixed it.
Caveat emptor: If you decide to go that route, make sure you can return the transformer if it doesn't to the job.
As an aside, I should buy a lottery ticket given the number of rare issues that happen to my Apple products.
I say this as a happy MacBook Air owner but i'm traveling soon and this had better not be an issue...
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.
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.
This doesn't actually provide contact to the existing ground pin, so you have this issue.
Time to buy a 3 pin adapter!
That's got to be noisier then an old ham radio.
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.
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?