Heatbed cable assembly problem
And... I should have searched before posting. https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/heatbed-cable-melted-down/#post-209430 had the same problem.
Additionally, I'm possibly a moron and it looks like I assembled it incorrectly in the same way as the poster above did. 🙂
lessons learned. Those screws need to be tightened down well. A little bit of loose and you'll get burning and too much heat. Glad you found out without any great damage.
Nasty one, I echo Dan's sentiments. Glad you found it in time.
Loose connections on cables can be very nasty if left for extended periods.
Saw it a few times at work with engineers who are a bit lazy, nearly set a huge M/C on fire with loose connections onto very heavy duty 24v lines.
And check them often, they can loosen.
Have these connections got star washers on them or is that just normal washers I see?
I know sometimes these are frowned upon, but certainly stop loosening