I have a rostock max v3 that i put a duet wifi in. It has worked great for about 300 hours and last night i was printing abs. Went good for about 2 hours and then the cooling fan kicked in for a bridge or something and smoke started coming off the board. Hit the power switch right away and had a look. Disconnected the cooling fan. (I use a berd-air with eswitch module) and tried the power. More smoke.
I disconnected everything and took out the board and the mosfet seems to be ok. The smoke seems to have been coming from the always on fan port. Cleaned it up a bit with IPA and desoldered the connection and it is quite damaged underneath.
i had 2 12v 0.1a 40mm fans connected in parallel to the always on fan port.
Does anyone have any ideas?