Hi
My rather new duet2 wifi rev 1.04b started to smoke when I was probing my bed. U3 burned a hole in itself just as others have shown in pictures.
I have used a 12V M12 inductive probe for 2-3 weeks, but yesterday I changed to a smaller 5V M8 inductive probe. (The 12V for the old probe was from an external step down converter.)
For the 5V probe, I used the 5V from the duet expansion connector. I would say that it did around 40 probe points, but then suddenly U3 started to smoke. My rail was 25.8V. No other active components were connected to the card more than the probe and the main PSU.
Anyone knows why? Have anyone checked the 5V AC power spectrum, with a 5V inductive probe connected and modulating the distance. My first thought when I found others with smoked U3, was regarding the phase margin of the closed loop of U3 when attaching a non-resistive load to 5V. But it is just a very wild guess.
I ordered the card directly from duet3d.com 16/04/2019.