User reports metallic taste in mouth when using laptop | Hacker News Reader

User reports metallic taste in mouth when using laptop

forums.macrumors.com

I’ve got an Intel Pro that would very slightly shock me when plugged in. It’d feel like the edge of the case had jabbed me a little, when it did it. I could imagine this being an electrical effect. User claims this has been while unplugged, though, so must be a different issue even if it is electrical.

Or maybe their laptop got exposed to some nasty levels of radiation.

Just posted a comment saying the exact same myself lmao

This is because your socket lacks grounding.

Your laptop's body is normally connected to ground and both power supply lines are also connected to it via two capaciators. No actual current is driven through it but it does have an effective voltage of ~110V on it unless it is actually grounded. You can feel that but it should be harmless.

This applies to most electric appliances.

Not the socket’s fault; it’s the charger. My MBP 90W charger doesn’t have a grounding pin. The 60W doesn’t have a grounding pin.

They have the hardware to be grounded (the metal T stub on which you attach the local plug), but they don’t come with the extended wire by default which has the grounding pin for the outlet.

In actuality, the reason you feel the tingle is because the case is effectively grounded to the neutral pin. The three phases are joined together at the transformer to create a cheap neutral, but because the load on all three phases are slightly out of phase, our body can feel the handful of mV being leaked.

I have an older (USB-A plug) tiny, official iPhone charger brick of that fold-out-two-blade sort which has become either terrifying or hilarious, depending on your temperament, by having whatever connects the two blades break. If you're not paying attention, it's easy to extend only one of the blades...

I've not attempted to charge with only the hot-wire blade extended, but I cannot imagine anything good would happen.

I really expected a 3rd party company to be producing 3-pronged versions of that adapter. In the UK the ground pin is a requirement as sockets will not fully open up the other two before the ground pin is inserted, and Apple's UK adapter has a metal ground pin, BUT still it's not connected to the 3rd internal prong of the charger. The extension cables that you can still buy separately, and that used to come free in 2012-2015 MacBooks have the 3rd prong, hence are grounded. WHY, APPLE?

> I’ve got an Intel Pro that would very slightly shock me when plugged in.

Oh, I remember this! Happened to me when traveling with my Intel-MacBook Pro to South Korea and perhaps some other countries.

That happens with the ungrounded two-prong power adapter connector (the one that comes in the box). If you have a three-prong power adapter extension cable, it won't do that.[^1] Apple used to include one of those in the box too, but they stopped around 2015 or 2016.

[^1]: https://www.apple.com/shop/product/MK122LL/A/power-adapter-e...

This is gold.

> I mean. My scientific mind would like to try ruling out variables. Stand over it without touching it for a while. Wear a gas mask. Stop chewing on it. See what works

I take the Amtrak pacific surfliner a lot and I've noticed that mac laptops will lightly shock me when they're plugged in. I think I've experienced this with 3 different computers over the past 6 years. Might be a useful data point, since I believe the train is an isolated power circuit independent from the power grid (the electricity is generated by the locomotive).

My M2 pro tries to ground itself through my arm on occasion when using it while it is charging so I wouldn’t put it passed apple

I’ve had this issue with all my MacBooks since 2010 with ungrounded chargers (because Apple don’t use grounded plugs for whatever reason although the contact exists on the charger).

Some years ago when I still had my 2009 Macbook Pro I noticed that if:

- The laptop was charging

- I was touching the laptop with one hand, and either (my memory is fuzzy on the details by now but it was one of these two circumstances):

- A friend was touching me on the side of the forehead with one hand and touching a crack on the wall with the other hand

- I was the one touching the crack on the wall with my other hand.

Again, I don’t remember which of these last two. BUT I remember the result: I would see banding with my eyes (very similar to what you see with cameras when their shutter doesn’t sync with AC power).

Now, our eyes don’t have shutters so I have no idea what was going on but I saw it.

Every Macbook or Macbook Pro I've had since ~2012 has had this issue. It doesn't present primarily as a "metallic taste", though. It's more of a barely perceptible tingle when my fingers touch the metal casing. It's especially noticeable when it's cold and when the ambient air is dry.

It only happens when I'm using the power brick with the two-prong "duckbill" plug; it doesn't happen with the old three-prong extension cable attached. From that, I assume it's a grounding issue.

I don't think those are related at all. One, the tingling is your body being used as ground. It's well documented and as you noticed, only happens when 2 things are true:

    * The battery is charging; and
    * The charger is ungrounded

If you read through the thread, OP says:

> only have tried battery so far.

https://forums.macrumors.com/threads/weird-taste-in-mouth-wh...

    If you feel liquid running down your neck, relax, lie on your back, and apply immediate  pressure to your temples. You are simply experiencing a rare reaction in which the Material Emancipation Grill may have emancipated the ear tubes inside your head.
      -- Portal

This could be "common mode noise" if the PSU is not grounded. There could be 100V on the chassis of the laptop. https://www.youtube.com/watch?v=wa1oLg7srOw

> When Apple writes that their new M3 MBA is the best laptop ever for AI, they should specify that AI stands for Artifical Intelligence, not Aluminium Ingestion, to rule out happenings like this.

Excellent.

Yes, I’ve experienced this with a MBP and Dell XPS (both Intel). It seemed worse when under load. I tried all sorts - cleaned the fans, re-applied thermal paste, Isopropyl scrubbed the case, replaced battery etc. The only thing that made a big difference was turning off WiFi on the laptop and connecting via Ethernet instead. Presumably something in the WiFi chip is off-gassing, or a dental filling is reacting to EMF in some way.

I'm just glad the person took it seriously and returned the laptop to be done with it.

There's always static electricity on MacBooks, especially in Europe!

I guess Apple switched to those new plutonium batteries:

https://www.independent.co.uk/tech/nuclear-battery-betavolt-...

...but only when sending an email more than 500 miles away?

Alternatively perhaps when above 3096 meters in altitude?

I've read the distance story (https://web.mit.edu/jemorris/humor/500-miles for the curious) but not the altitude one. Do you have a link handy?

James Ziegler and W Lanford first detected sea-level single-upset events in 1979 and in the decades following much of the research was done in Leadville, Colorado which has an altitude of 3096 meters. Unfortunately I can't find a link for the 1979 headscratcher at the moment. I will edit this comment if I do.

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