Comment by 420official
14 hours ago
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
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
> 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.
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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.
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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
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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.
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.
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No way, that's why it's "fixed" sometimes, thanks
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).
Maybe you're holding it wrong? j/k
Seriously though, that does not sound safe at all.
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!
Have you ever had that looked into it maybe just ask AI? That does not seem healthy.
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.
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.
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.
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?
Aluminum should oxidize essentially instantly.
Anodizing and oxidation are 2 totally different things.
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.
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.
but it's never going to be grounded, there isn't even a ground pin on the charger
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...
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Apple sells a 3-pin extension cable
US Version: https://www.apple.com/shop/product/mw2n3ll/a/power-adapter-e...
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>The charger also gets hot and sparks.
Some heat is normal, but the sparking seems concerning.
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.
So glad to know it wasn’t just me with sweaty hands and pitted aluminum that is razor sharp!
Holy moly, that guy in the reddit post needs to see a dermatologist asap and figure out why their skin is emitting acid.
It is within the range of physiology. Nobody has pH-neutral skin, and aluminium is reactive.
https://en.wikipedia.org/wiki/Acid_mantle
Oh wow I think I have a mild version of this.
Can it cause the plastic on the mouse to break down?
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)
You need to moisturize more.