Replaced the Mainboard in our R2 which fixed the reading of the thermistors but now heating the bed only turns on the cooling fans. No power output to the bed (though the led turns on). Manual fan control does nothing. Bed wires are soldered to the board, and it heated up once then started this. (Maybe I shouldn't have messed with the firmware?) Hot end heats up fine. Have tried 1.2.4 and 1.2.6 firmware, R2-generic-image on the Pi. Help please and thank you.