[420official]

I just did this to my MacBook not because of the sharp edge but because the pitting turns a sharp edge into a sawblade. Something about the grounding on on the frame when plugged in mixed with my sweaty hands leads to damage along this sharp edge on every MacBook I've ever owned.

See https://www.reddit.com/r/macbook/s/hbyVh5SJhw for another poor soul with the same caustic skin

[CGamesPlay]

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.

[userbinator]

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

[Doxin]

> 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.

[normie3000]

> 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?

[sitharus]

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.

[ranger207]

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

[numpad0]

Only Apple is insane enough to make actual laptop chassis with unpainted anodized aluminum. Others either do it in plastics and/or painted metal. And paints are kind of liquid plastics.

[RealityVoid]

It's not only mac's suffering from this problem. My old dell latitude with magnesium case had the same thing. I didn't fully understand why and some people thought I was mad for feeling it but it was there.

[normie3000]

Additional question: why do only some people notice?

[sitharus]

It’ll depend on how well grounded you are compared to how well grounded the laptop is, where it’s touching your body, and your sensitivity to electricity which varies.

[wazoox]

My aluminium body Lenovo IdeaPad has exactly the same problem.

[black_puppydog]

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

[robotbikes]

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.

[ebbi]

Is that what it is! On my pre-unibody MBP I used to run my finger across the body sometimes and it had this weird wavy feeling (honestly can't describe it well). I thought it was just a quirk of the aluminium itself!

[Jolter]

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.

[erincandescent]

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

[msephton]

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.

[SeasonalEnnui]

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.

[normie3000]

Disappointing. I understood Neo doesn't come with a power plug in UK; was yours the official one?

[msephton]

It was just me trying one in the Apple Store

[throwaway290]

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

[p_l]

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.

[throwaway290]

all my EU/UK macbook plugs I got from apple are always grounded, metal prong and metal side pins

so what I mean is maybe house electricity grid is not grounded.

[swiftcoder]

> all my EU/UK macbook plugs I got from apple are always grounded, metal prong and metal side pins

The short version, where you remove the extension with the 3-prong plug and attach the plug directly to the charger brick, is only available in 2-prong in the EU/US (the UK thankfully still gets all 3 prongs in this configuration)

[p_l]

UK plugs are always grounded because there is no ungrounded version.

But elsewhere you only get grounded plug if you buy extra extension cord for the apple power brick, otherwise it's only ungrounded.

[normie3000]

My experiences are all from third-prong countries.

[vinay427]

To add to this, I notice this more frequently in the UK and EU countries than in some other parts of the world (although it varies within each country quite a bit).

[Brian_K_White]

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.

[ajam1507]

Using a 3 prong extension cable on the charger will prevent this.

[imglorp]

How? The (US) charger's only got 2 pins so ground stays unconnected.

[pxx]

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...)

[jahnu]

Got a bunch of cheap ones from Ali Express and they worked fine.

[BobAliceInATree]

Apple sells a 3-pin extension cable

US Version: https://www.apple.com/shop/product/mw2n3ll/a/power-adapter-e...

[bombcar]

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.

[Tsiklon]

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

[15155]

There's zero chance that the DC ground in the laptop is tied to earth ground in the charger: they use LLC resonant converters and flyback converters (depending on vintage) - an earth ground tie would defeat the purpose of these isolated topologies.

[jahnu]

However it’s wired up the fact is the electric buzzing feeling goes away if you use a grounded extension cable instead of two pin.

[namibj]

No they isolate L and N not PE.

[CGamesPlay]

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).

[Barbing]

No way, that's why it's "fixed" sometimes, thanks

[rlonstein]

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.

[leptons]

Maybe you're holding it wrong? j/k

Seriously though, that does not sound safe at all.

[al_borland]

This comment is concerning.

> acidic sweat. once you got through the anodization the raw aluminum wears faster....

If one files off the sharp edges, won’t the sweat eat through everything faster, as that protective layer was filed off.

[crdrost]

Probably. But, the time when the laptop is taped off would be uniquely a good time to hit it with some polyurethane or something clear to protect it from that sort of damage? Just make sure you hit it with compressed air first so you aren't gluing the aluminum dust to the chassis?

[compass_copium]

Aluminum should oxidize essentially instantly.

[themafia]

True; however, this is an aluminium alloy. These typically have lower corrosion resistance and are most commonly anodized because of it. The applied layer is typically 3 to 5x thicker than that formed by pure aluminium oxidization.

[nikisweeting]

You're off by at least 3 orders of magnitude, anodization is like 1,000x~5,000x thicker (5~25µm) than the natural oxide coating (~5nm).

[lukevp]

Anodizing and oxidation are 2 totally different things.

[Brian_K_White]

anodizing is literally oxidizing

[nikisweeting]

Yes but anodization implies thickness around ~5–25 micrometers (µm) for aluminum. The natural oxide coating is ~2-5 nanometers (1,000–5,000× less thick).

[esskay]

Huh, I've had that pitting with every magic mouse I've owned, the sides of it end up looking like a cheese grater...apparently my fingers are acidic!

[roysting]

Have you ever had that looked into it maybe just ask AI? That does not seem healthy.

[Jolter]

It’s extremely common and nothing to worry about. As a brass instrument player, I sometimes come across someone whose instruments always deteriorate at 300% of the rate of others. Laquer peels, silver plating blackens, etc.

[roysting]

Thanks. That’s astonishing to me. As far s as I know I’ve never come in contact with people with acidic skin/excretions like that.

[dataviz1000]

I’ve been traveling around the world. It is 50 / 50 of the socket is properly grounded —-anywhere in the world. I get a tingling zap on the wrist when not properly grounded. The charger also gets hot and sparks.

[ddlsmurf]

but it's never going to be grounded, there isn't even a ground pin on the charger

[BobAliceInATree]

Apple sells a 3-pin extension cable

US Version: https://www.apple.com/shop/product/mw2n3ll/a/power-adapter-e...

[intelkishan]

Yeah they sell the 3-pong extension for various countries. I am currently using the Indian version of it.

[russelg]

If you swap in the extension cable head, that does indeed have a ground pin, at least in Australia anyway. The grounding comes from that metal ring that the connector uses as a guide. https://www.apple.com/au/shop/product/mw2n3x/a/power-adapter...

[ddlsmurf]

only two prongs of which make it through. Usually the regulation as I understand is that it's fine if you can prove the case can never get in contact with anything electric, for most laptops that's just being made of plastic.

[bragr]

As has been established in other threads here, the metal button thing the prongs slide onto is an earth connection.

[ddlsmurf]

Just take an apple charger and a multimeter, try to find a path to ground from the computer side, I'll wait. Plugs have regulations on how they can be built which are different from how they must be connected.

[masklinn]

> only two prongs of which make it through

The big recess above the pins is what encases the button of the charger and provides grounding if it includes metal strips. Assuming the charger itself has a metal button.

In the EU a grounded cable has been the default forever (I have a grounded cable from my 2010 MBP which I use as travel cable for my 2021 MBP)

[OJFord]

Which makes it non-compliant in the UK, and no doubt elsewhere too. I don't understand how Apple (hardly a small fly-by-night!) continues to get away with it.

[shawn_w]

>The charger also gets hot and sparks.

Some heat is normal, but the sparking seems concerning.

[leptons]

That should not happen with a well designed power supply. It sounds like Apple cut some corners "for design reasons", or some shortcut to make it cheaper to manufacture.

[Esophagus4]

So glad to know it wasn’t just me with sweaty hands and pitted aluminum that is razor sharp!

[greazy]

Oh wow I think I have a mild version of this.

Can it cause the plastic on the mouse to break down?

[bluGill]

Yes, it is fairly common with some plastics. better plastics won't but there are a lot of different plastics with differt formulas (and many can be mixed)

[BoredPositron]

You need to moisturize more.

[greazy]

Im an anxious person. I sweat from my hands due to anxiety and not dry hands.

[sanj]

I’ve noticed that this only occurs when I use a two-prong adapter for the power brick.

If I use the 3-prong, which is usually tied to a long cable, I don’t feel the buzz.

I assumed that the additional grounding helped.

[chubs]

Holy moly, that guy in the reddit post needs to see a dermatologist asap and figure out why their skin is emitting acid.

[CarVac]

https://en.wikipedia.org/wiki/Acid_mantle

[psd1]

It is within the range of physiology. Nobody has pH-neutral skin, and aluminium is reactive.