3 ms·

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

by 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.

by kosma 10y ago

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.