Comment by CGamesPlay
6 days ago
Oh is that why it happens? Was wondering why the spot directly under my wrist was pitted into a sawblade. I also filed it, though just enough to remove the pitting, nothing like the OP did.
It's easy for me to feel the mains frequency while gently rubbing the top surface of the MacBook while it's plugged in. Really feels unsafe, but neither me nor the computer have suffered any serious injuries yet.
Really feels unsafe, but neither me nor the computer have suffered any serious injuries yet.
That's due to interference suppression capacitor in the PSU. The safety standard puts the "touch current" limit at something like 300uA (0.3mA), which is definitely in "painful but not dangerous" territory. You do need to exercise caution when plugging in other devices that are also connected to the mains, since that amount of current and voltage can certainly damage sensitive electronics.
Old but good page on such measurements: http://www.aplomb.nl/SMPS_leakage/Doc_ie.html
> since that amount of current and voltage can certainly damage sensitive electronics
Like for instance the magic mouse. I've completely destroyed three magic mice by sometimes accidentally touching the mouse to the laptop. It'd not do much of anything initially, but at some point touching them together would kill the connection for a couple seconds, and over time it evolved into the mouse just refusing to connect altogether.
I'm glad my boss pays for this hardware because I'd be incensed to have a mouse THAT expensive break that quickly.
> It's easy for me to feel the mains frequency while gently rubbing the top surface of the MacBook
I haven't been a regular Mac user, but I've had maybe 3 work MacBooks since 2010 and I recall having this issue with all of them.
Why haven't they fixed it?
They can’t, it’s caused by the capacitors required to suppress electromagnetic interference caused by the switch-mode power supply. These allow a very very tiny amount of current to leak through from the mains side, which is then capacitively coupled to the metal case (IIRC Apple do not connect the case to power negative) reducing it further, but it’s enough for humans to sense it.
It can be avoided by using a grounded power supply, but because there are large countries that have ungrounded outlets in common use the most designs are ungrounded.
Why do only Macbooks suffer from this problem? When I had a work-issued Macbook I charged it and my personal Framework off the same USB-C charger and I only every felt the leaking current from the Macbook
5 replies →
Thank you for explaining this! I've been feeling this on my girlfriend's macbook for years and I've always wondered what the hell that was. :D
I once had an HP with an aluminum case and it had a grounded power supply but if you plugged it in without grounding his an adapter (sometimes you gotta do what you gotta do). You could feel it straight up vibrate while conducting current if you rubbed your hand over it. Not enough to shock me but it felt like kind of a shoddy design and leaked a lot more current than I've felt on a MacBook.
1 reply →
Definitely been a long standing issue on many laptops with exposed metal parts. Late 90’s, if I used my brother’s Compaq while putting my feet up on the radiator, the metal speaker grills would give me mild shocks.
You can fix it by switching to one of the grounded charger heads. Unfortunately in most locales those are only available with an integrated extension cable (or as everyone seems to call them, the "gooseneck" cables)
It happens with other 2-pin chargers on both MacBooks and other laptops, but it depends upon various factors how strong the leakage is
It's also an issue on the new Neo. It was the first thing I noticed when I tried one in the Apple Store. I unplugged the power cable and it went away, replugged and it came back. I'm in the UK so I expected grounded electricity supply.
If you buy the UK 1.8-metre Power Adapter Extension Cable, this has a metal ground pin that grounds through the metal clip on the power brick. I switched all my MacBook & iPad chargers to this, no more earth leakage sensation from metal casing.
Disappointing. I understood Neo doesn't come with a power plug in UK; was yours the official one?
1 reply →
You wouldn't have this if your plug was properly grounded. Most developed countries have plugs that have grounding. EU via side pins UK via third prong
Apple avoids shipping grounded plugs as if it was personal affront to Ive. Also caused many many times for me to be shocked with electrostatic build-up.
5 replies →
My experiences are all from third-prong countries.
1 reply →
I have super dry skin and I also feel that weird ac effect when lightly touching and moving along the surface of pretty much any aluminum mac device since they started making them aluminum.
And almost no other device I've ever used. My aluminum Framework does not do it. My wifes magnesium LG Gram does not do it.
I have felt it on other things but only extremely rarely. It's bizarre that whatever it is they're doing different, it's probably wrong, and they've kept doing it in every device for decades.
To describe the effect in more detail for anyone who doesn't already know: It's like the case is alternately grabbing and releasing your skin at 60hz.
It's a bit like chatter, ie the periodic friction you use to ring a wine glass by wetting the rim and then running your finger along it. It rings because the combination of the friction, the lack of friction from hydroplaning, and the rubbery give of your skin, makes your skin alternately grab and release 30,000 times a second. Only in this case you are only barely touching the case not pressing enough to make any friction or make a squeal noise. It's like static electric charge attraction. Just touching the case you feel nothing, but move your finger along the surface and you feel it vibrate your finger without any friction to explain it.
It's unsettling and displeasing, which are strange words to expect from an apple device at least when you are only talking about the design and not the tech stack or corporate behavior. It makes me think of cheap electronics from a country with no consumer safety regulations that will probably burn down every 3rd house they wind up in.
It's probably harmless, but then again a lot of things that are harmless in short infrequent doses turn out to have been harmful after you did it for 10 hours a day for 20 years.
Using a 3 prong extension cable on the charger will prevent this.
How? The (US) charger's only got 2 pins so ground stays unconnected.
There are grounded duckheads for this purpose, e.g. https://amzn.to/4cnzuef (note out of stock. I guess your best bet is to use a UK duckhead, but half of those have a dummy ground...)
if you take the plug part from the brick you'll note that there's only two pins but the button-like thing is a ground
as noted in a sibling, the power adapter extension cable does plumb the ground through (https://www.apple.com/shop/product/mw2n3ll/a/power-adapter-e...)
1 reply →
Apple sells a 3-pin extension cable
US Version: https://www.apple.com/shop/product/mw2n3ll/a/power-adapter-e...
I don't know if this link will work - https://www.chargerlab.com/wp-content/uploads/2022/06/202206... but that metal round pin thing is a ground; and the three-prong cable connects to it.
The extension cable they used to include in box with the computers, it has the third pin for the charger brick connector which is wired to ground
3 replies →
That cuts it by about 90%. But as others have said, the default US plug doesn't ship with a ground pin (though the extended cord does IIRC).
No way, that's why it's "fixed" sometimes, thanks
Finally. Someone else has mentioned this, I thought it was just me who I experiences the sensation of there being stray current on MacBook frames.
Maybe you're holding it wrong? j/k
Seriously though, that does not sound safe at all.