But I have seen laptop chargers with earth/ground, I guess it depends.
From the overall description it seems to me more likely that for some reasons only indirectly connected to the poor grounding the AC unit introduced some kind of spurious (or stray) voltage on the neutral.
> But I have seen laptop chargers with earth/ground, I guess it depends.
All the mac chargers I've had had a grounding pin.
Whether they're actually grounded depends whether you're using the wall-wart adapter or the cable: in europe at least the cable has a grounded plug, the wall wart is just a europlug.
> The MBPs I've had only came with an USB-C charger.
That's not exclusive, USB-C has ground pins.
> Those come with a Europlug, which doesn't have an earth connector.
Yes, but if you remove the europlug you should see that the charger has a metallic nub onto which the adapter clips. The 140W charger has one at least, and so did the old 85W chargers. Non-earthed chargers (e.g. iphone chargers) have a plastic nub instead.
As I wrote the europlug adapter is not earthed, but the cables (with a CEE 7/7 or whatever the standard is in your country) are earthed. I'd assume the UK wall wart adapter is also earthed but I've never seen one.
You can see the earthing on the charger side of the cable, because it has two metallic strips inside the recesses, to connect to the nub.
That's a circuit ground, not an earth ground. It's not for connecting the device to an earth pin.
> if you remove the europlug you should see that the charger has a metallic nub onto which the adapter clips.
I see. I looked at mine, a 61W adapter. Interesting that they chose to use a C7/C8 connection with a separate metallic nub, instead of a C5/C6 Mickey Mouse connection.
I actually measured that Dell USB-C chargers forward grounding to the outside metal of the USB-C plug, and the laptop actually uses that grounding for its chassis.
This confused me, because there's definitely no pin for an earth ground in an USB connector. So I decided to repeat your experiment and see which pin it uses.
Turns out, it's the cable's shield that carries the earth connection.
That's really cool, so the connection ground is in the cable, but the earth ground is the connector itself? Is that part of the spec or just something which sometimes happens?
I don't know if it's specced. I couldn't really find anything more than the pin diagrams on Wikipedia ( https://en.m.wikipedia.org/wiki/USB-C ). Those don't mention earth ground at all.
But since both Dell and Apple are doing it, I guess it's at least an optional thing they can do.
There’s a metallic ground pin but that doesn’t necessarily mean much, I’ve got an iphone adapter (from the world kit) which is the same and is ungrounded (because the old switchable power adapter has no ground nub).
You need to check the back of the plug, the nub of the charger (which is metallic) slides into a rail thing. With the cables, the rails have a metal strip to connect with the charger’s nub: https://discussions.apple.com/content/attachment/8ec896d8-54...
https://en.wikipedia.org/wiki/Appliance_classes#Class_II
But I have seen laptop chargers with earth/ground, I guess it depends.
From the overall description it seems to me more likely that for some reasons only indirectly connected to the poor grounding the AC unit introduced some kind of spurious (or stray) voltage on the neutral.
https://en.wikipedia.org/wiki/Stray_voltage