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Comment by ilyt | Hacker News Reader

Interesting, most notebooks are not connected to ground. Maybe ground connection came from peripherals (USB Hub/monitor etc.) ?

> Again, the same pattern came up: the wrist-rest was only uncomfortable when running on AC power.

Guy's getting lightly electrocuted...

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That's due to a class-Y capacitor in the PSU used for EMI filtering. Honestly it's harmless and you'll even see this issue on a MBP if you don't use the three prong cord that has a ground. Normally it's so slight that you don't feel it but if you lightly rub your finger over the chassis you can sort of feel a texture to the surface that's not actually there. It's 60Hz but it feels like ridges on the surface and it disappears if you unplug it or plug it in using a grounded cord.

https://www.allaboutcircuits.com/technical-articles/safety-c...

I've felt that faux-texture phenomenon if I rub a finger on the stainless-steel surface of the dishwasher's door in the apartment I'm currently renting (living in a ~50-year-old flat I'm the Netherlands, though the dishwasher is almost brand-new). Would a similar cause of lack of grounding be at play here?

Until you get that looked into, I'd take extra care not to simultaneously touch the door with one hand and any possibly solid ground e.g. water pipe with the other.

Thanks for the suggestion. I realized something was amiss when I was placing a rinsed plate on the dishwasher and by accident touched the wet steel of the kitchen sink. I was lucky that it was only a small tingly shock. However, I've had trouble in convincing the landlady to fix it, since the contract stipulates that I need approval for any modifications.

Possibly, at least in my case the inside metallic parts in inside of dishwasher are directly (and by that I mean resistance is less than ohm) connected to ground.

Normally any leakage would be shorted to ground (and if too much and house has RCD, trigger protection), but if there is weak one, or none (some of the old houses even have only 2 wire install, with "ground" pin just connected to neutral)

No clue what electrical in the Netherlands is supposed to look like but it sounds like it's a floating ground if you're sure you're feeling the same effect. Grab a voltmeter and check and if you're seeing 60-70V AC then it's probably EMI filtering. It's completely safe and doesn't present any kind of shock risk other than the fact that it's an indication that the chassis is ungrounded which means you don't have the added safety of shorting out the circuit if a live wire came loose inside and energized the chassis.

Personally I miss the days when protective earth was protective earth and you didn't have to worry about engineers doing foolish things like using it for EMI filtering or any sort of current path, even if miniscule. The safest class Y capacitor is the one that doesn't exist.

Thanks for the suggestion, I'll see if I can get my hands on a voltmeter. I too miss the days when things were engineered for safety and durability.

It can be due to the cap in the laptop power supply, but here more likely case is as OP is guessing, the ground stopped being ground and the leak is somewhere else in power network. And that can be way more dangerous than just a tingle, disconnected ground means that even line directly connected to ground would not trigger any safety (especially if house is old and also don't have RCD).

I think it was a notebook with aluminium frame, which would make grounding appropriate.

I had a Dell XPS 15 with aluminium frame once and discovered that it was grounded when I was in a hotel abroad with no ground on the outlets and – my wrist-rest got uncomfortable.

I then quickly fudged some wire from the notebook to a radiator, though.

Guy's getting lightly electrocuted...

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lightly shocked, lightly electrocuted is like being lightly decapitated.

We actually have this issue in our 6 year old office, so not exactly old electrics. Running laptops off non-grounded plugs causes that typical "vibration" / buzzing feeling throughout the chassis of the laptop.

As in laptops that work fine in other place ? Sounds like electricians fucked something up...

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