F3 fuse short on auto level

hi all, my f3 fuse popped (already confirmed) and possibly more during the auto level process. I know wire brush / metal to metal contact on the hot nozzle is a big nono, but im trying to figure out wtf happened to short it this time around. i should add that i recently swapped the rambo board from 1.3 to 1.4, and it turned on fine, flashed firmware, let me change filament, moves around and so on. i tried to run a test print and when the nozzle hit the first level point it blew. i’m triple checking my connections, but everything looks right and i cant seem to figure out what is triggering this. thanks!

Well that fuse is the 24 volt power that is used to power the heat cartridge in the hot end, and the bed probe points are ground. So it sounds like you have a short between the cartridge and the hot end body near the nozzle. The small metal plate that holds the cartridge in the hot end may have shifted and shorted to the wires right where they come out of the heat cartridge.


Thanks for your reply! That’s what I thought too - until I plugged a different extruder in and it shorted again. I’m thinking it’s somewhere on the board, but I’ve triple checked my connections and they all look correct!