A few days ago I managed to overshoot the config defined max temperature for my hot end- this caused things to shut down and I got a fault/warning in Pronterface, but now the small mosfet I had running the hotend and the LED above it are constantly powered. I read about this happening to a few different people, so it is nothing new. The small mosfet looks burned.
I noticed my more recent trouble toward the end of a 26 hour print. Both the input connector and the big mosfet connecter (2.5) for my heat bed were burned partially black. The print finished, but once the power to the bed was cut, it was gone forever. I can no longer get either 2.5 or 2.7 to power up- the LED stays off and I can measure no voltage. I am getting 12 volts to the input connector still. I re-read the setup instructions and noticed that I glazed over the fact that the mosfets require cooling if drawing more than 12 amps. I did the calculations and my current 12 volt, 270 Watt heater overshoots 12 amps by a bunch. Huge mistake on my part.
I have on the way from China a 110 volt silicone heater I had planned to run with a solid state relay, but with just one functional small mosfet, I can run either a hot end or a relay controlled heated bed, but not both.
There is visible discoloring on the board and a few components radiating up from those scorched connectors. Is it likely that a lot more than just the 2 big and one small mosfets need to be replaced (plus the burned connectors)? It seems like two different problems since the small mosfet is always on and the big mosfets are just dead. I successfully completed a print with PLA last night, so the board seems to function just fine other than the loss of the mosfets. Is it worth buying the replacement parts, or do I need a new board?