I found a USB Cellular data adapter in the trash and plugged it in to my MacBook Pro, which instantly shut down.
Rebooted, and the USB port did not work. Shut it down and left it for half an hour, and, yay, all working again.
Disassembled the adapter. Turned out to be a dummy used for display. No guts, just a steel bar across all four pins of the USB connector. Looked real from the outside.
It was a very, very stupid thing to do. Thank-you Apple for putting a self-resetting fuse in my MacBook Pro. Saved my idiot butt.
Re:Bad USB-C cable destroys laptop
by culturestate on Wednesday February 03, 2016 @07:26AM
(#11026066)
Plugging random USB devices into your computer is a bad idea, full stop -- miswired or not. "I found this in the trash and plugged it in" is the bane of CISOs everywhere.
This was an A-C cables, which means it was used to charge the laptop, not to power something from the laptop.
Current limiting doesn't magically protect powered devices from voltage reversal (-5V instead of +5V), so both the laptop and power delivery analyzer went poof.
They may have taken enough current to trip charger's current limiter, but then it was a bit too late.
The basic USB spec requires that all ports be protected with a small self-resetting polyfuse for exactly this reason. I don't know if the Type-C or USB 3.1 specs includes something similar - I would assume so but perhaps the additional current capabilities made that infeasible.
http://elinux.org/Polyfuses_explained
A standard USB polyfuse usually resets pretty fast (as soon as it cools down) but they could take up to a few days. It's also possible the manufacturer cheaped out and didn't include a polyfuse, of course.