melzi board overheating extruder

messed up my original extruder heater/thermal replaced it. now i am getting constant power to hot end as soon as printer turns on wont stop heating without trying to heat it.

power on melzi board also overheated and burned the connectors; no idea whats wrong.

most likely the mosfet driving the heater is bad sending constant voltage , and i think they are surface mounted making it tricky to replace you could start a new post how to replace

what exactly is the mosfit that would require replacing what would I buy? If the melzi boards fixable I can try I have soldering tools to do it with if thats whats required.

the mosfet on mine has an aluminum heat sink on it and is located beside a green screw terminal block that the hot end heater connects to and is surface mounted on the board. the heat sink will lift off showing the part as far as part number it may show it or a melzi schematic in simple terms its an electronic switch that cycles heater off and on in tech terms metal oxide field effect transistor

Ok thanks; hopefully that is what needed to be replaced was thinking of just selling the board.

Edited 1 time(s). Last edit at 12/07/2016 03:21AM by merchant1307.

That's what happened to my chinese Melzi board within weeks from new.
I dumped it and changed to Ramps 1.4.