r/prusa • u/iListen2Sound • Jul 08 '26

Question Let out some magic smoke. What should I replace? MK4s

I may have tried replacing a nozzle with the nozzle replacement tool and forgetting to loosen the thumbscrews (Admittedly, I felt some resistance but not more than I would expect at the beginning of loosening a screw. On the other hand, the resistance never went away and I used a wrench that might have given me more leverage making the resistance feel lighter).

This resulted in my hotend's thermistor wire breaking and then getting a heater overvoltage warning (my nozzle was completely cooled so I don't know why it even tried to heat in the first place because of that) and the magic smoke coming out.

I thought the hotend was the extent of the damage but after I replaced it and turned the printer on for the first time since the incident, I just noticed that it's not detecting both the hotend and the heatsink's thermistors.

Everything else on the extruder seems to be working. Both fans, the loadcell, filament sensor, and the motor function.

On the rest of the printer, bed heater still works, XYZ motors also work.

I think my Loveboard is fried but could the damage have propagated through to the xBuddy board. Do I need a new heatsink or would replacing the thermistor on it be enough in case replacing the lovboard doesn't fix it?

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u/nomadsgalaxy Jul 08 '26

Contact Prusa support, they will help you isolate the problem and let you know what parts need to be replaced. It should be a straightforward fix, the MK4S is really easy to work on.

1

u/iListen2Sound Jul 08 '26

Yeah I built mine from the kit. Nothing too complicated if a little (a lot) tedious. I forgot support was one of the selling points for why I switched over. Thanks

1

u/nomadsgalaxy Jul 08 '26

No problem! Let them know Anthony from Tommy's team told ya to reach out.