@Phaedrux As far as I can tell, there are no scorch marks or chips with burn holes. The CPU does not get hot, nor does the wifi module nor the SD card slot. The only thing that heats up seems to be U11.

This Duet was purchased on September 10th from Spool3D

On the wiki link, I have the 3rd bullet on the voltage indication leds, that the red LEDs are lit even while everything is disconnected. Removing the SD card makes no difference, and trying the ERASE jumper as per the instructions results in no change.

Could you clarify what you meant by "Check for shorts on your hotend"? As in, with the everything disconnected, use the continuity meter to test the for shorts across the outputs for E0/E1/E0_Temp/E1_Temp? If so, I just did that and there are no shorts as far as I can tell with my meter.

Attached is a clearer picture, plugged into USB - unfortunately, I think that this is as good as my phone camera can get; are there any specific areas of the board you'd like a picture of? I can try to take a closer/clearer picture of those areas.

Hello,

I recently purchased a Duet 2, wired it up, and was printing fine with it for about a day, on and off, calibrating it while being in and out of the room. At one point I went and changed Z-steps in the config.g, hit the save and restart button, then left the room to eat.

On coming back, the Duet had not reconnected, and the blue LED on the network chip had stopped lighting up, along with the lights on the side. I was very confused so I hit the reset button, upon which it seems that the mosfets all closed and my PTC heater and bed turned on. Mildly spooky, but I turned off the power and unplugged everything, leaving only 24V power plugged in, after which it seemed to turn on (Vin and and 5v LEDs light up), but the LED indicators for the bed and E1 were on (I don't recall if the one for E0 was on). I accidentally touched U11 and it was very hot. Unplugged everything and plugged it in on USB and it wouldn't show up on Device Manager on Windows 10, but the 5V and VIN leds continued to light up.

Probing the rails it seems that 3.3V rail reads about 0.5V and the U11 chip continues to get very hot. Looking up possible reasons why this happened it seems like somehow the 24V and 3.3V rails shorted, but nothing was moving and the wires were fine/worked earlier in the day.

Any ideas on what to do/test?

Edit: Attached pictures of the front and back of the board as it is right now, everything unplugged, here https://imgur.com/a/Pxd7n8S