Flux issue?

  • Hello all! I was moving an axes and had the 4 lead screw gantry jam. This caused some of the steppers to jump steps. Now, I get a stepper drive shorted to ground on driver 2. I checked the wiring for shorts and found none. I am still getting the error when the motor is unplugged. Upon inspection, one of the driver MOSFETs and some other components where covered in a thick off white substance. Flux. Cleaning gently with a q tip and 91% isopropal I was able to get most of it off, but I think some is under the bottom most driver 2 mosfet IC on the HC6 0.6 V board. I have a photo attached of the after cleaning. You can see some corrosion on the electrolytic cap as well as some flux on the SMT (c215) cap, and the MOSFET (Q19).

    Thanks for taking the time to read this!


  • that flux is everywhere, under the chips too, it's normal and expected, it is no-clean flux so you do not need to clean it, it does not conduct electricity.. (even most of the flux solutions that are not "no-clean" do not have to be cleaned)

    "stepper shorted" usually means driver (or in case of duet 3 that comes with external fets, the fet) is dead. this is not supposed to happen on jam but if any of the motors had a lose wire that can blow the fets on the output (attaching/detaching motors while driver is enabled)

  • Hmm, Ok. What do you think caused the corrosion on the cap's Solder joint then?


  • Looks more like a bad solder paste disposal in that area. Clearly the Q19 transistor soldering looks significantly different from the others. Maybe some dirt between the PCB and the mask having the final effect of too much deposited solder paste?

  • @Catalin_RO

    Thanks for looking! That might be it.

  • administrators

    Flux isn't normally white. My guess is that one of the mosfets failed and the white gunk came out of it. Do you have a photo of the board before you cleaned the white gunk off?

  • unfortunately I do not.


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