Removing Heater Mosfet



  • My last post (dead thermistor) established that I had shot the E0 Mosfet on my Duet3d 2, I've since established that the thermistor is functioning fine,
    I would like to repair the board but am wary of removing the original Mosfet as I only have a basic soldering iron.

    Some questions

    1. Is there a way of piggy- backing the mosfet by cutting the two pins soldered to the board and mounting the new one on top, if so how?

    2. Is the heat sink effect of the board essential ?

    3. Would using an Arduino controled 12v hot end placed under the mosfet, provide enough heat to enable me to desolder it?

    4. if so, at what temperature should the backing block be?

    5. Any other ideas?



    1. No, its a three terminal device, i.e. the tab is also a "pin" (ed well, you could join the tabs, but you'd loose on the cooling in the next step)

    2. depends on the current, but most likely yes.

    3. no idea (ed hotbed would be better suited maybe?)

    4. pre-heating is normally around 100C, never more than 150C and then only for a brief moment if needed.

    5. use an external mosfet module instead , or use E1 output instead?



  • Soldering/Desoldering mosfets is relatively easy due to the low pin count and doesn't require too much equipment (my favorite soldering iron for this kind of jobs is only $13 on Aliexpress).

    a. Can you post a picture of your 'basic soldering iron' and tips you have?

    b. Do yo have experience soldering components on PCBs?

    One option you have is finding somebody that is comfortable doing similar soldering work. E.g. a phone repair shop or a maker with more experience.

    BTW, if you want to practice, you may want to get one of these https://www.aliexpress.com/item/4000065156619.html



  • @zapta Thanks for your reply. My soldering iron is a single point 30w basic (Chinese?) iron, but your suggestion to find an experienced started me thinking and I managed to contact a professional electronics engineer friend who has offered to do the work, I think that is the safest approachIron.jpg



  • @CrazyJane, I am glad that you have a solution that may work.

    The soldering iron you have has conic tip which is not great for PCB soldering (compared to let's say a chisel shape).

    If you want to get good soldering irons for a reasonable price I would recommend the chinese temperature control ones such as https://www.aliexpress.com/item/4000129151281.html or https://www.aliexpress.com/item/32978285416.html. They accept 900M style tips (many available on Aliexpress) and have useful feature such as very fast heating, temperature stabilization, auto sleep, and some even have auto wakeup.



  • @zapta Thanks for your interest, much appreciated,


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