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Don't fry your PCB! Check your wires. UM3, S3 and S5


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Posted · Don't fry your PCB! Check your wires. UM3, S3 and S5

Hi everyone,


Our S5 died recently, and it's taken a while, but I figured out why. Save yourself the hassle now, check two things.


Check the heat shrink on the print head capacitive sensor. Replace if worn.




Check your nozzle heater wires aren't sticking down. And if they are, check if the insulation is burnt/worn. Bend the wires up out the way.




The issue itself if best shown with Ultimaker 3 CAD files, see below. Obviously the tab is bent on the machine, but if the wire sticks down, it hits the tab. The wire is hot, the heat shrink wears away, 24V from the heater fries the PCB on your print head. Auto levelling fails, no way to turn it off, machine is out of action. 





I suspect this is a known issue, you can see below the tab direction and the inclusion of heat shrink is a design modification. Picture below taken from UM own website on diagnosing levelling sensor issues.





Our 18 month old, lightly used S5 now needs a new print head PCB, I had to diagnose this myself as UM support just wanted me to send in the whole print head. Of course, this is out of warranty, so an unwelcome time and monetary cost. 


Save yourself the hassle, stop this before it eventually wears out the janky insulation. 


Please let me know if you've suffered the same failure. On our machine it was the U8 chip that let out the magic smoke.







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Posted · Don't fry your PCB! Check your wires. UM3, S3 and S5

Hello, I think I have the same problem.    Could you tell me what the normal voltagecheck is on the bed calibration sensor.   This could be a good indicator if this is the problem.   🙂

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