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  • Thermomix TM31 motor RPM jumping

    Thermomix TM31 motor RPM jumping 1 fixbear updated 1 month, 1 week ago 2 Members · 5 Posts
  • Thermomix TM31 motor RPM jumping 2

    okwestern

    Member
    January 12, 2020 at 9:25 am

    My Thermomix TM31 have started jumping up and down in RPM. I set it to say 7 and it idles up in speed, then falls gradually, then jazzes up to 7 again, falling. Often when i run it to high rpm it makes noise, as it is slightly crushing/vibrating, but the motor spins freely and nice, without any noise when manually turned. Bearings seems fine. I figured the noise comes from the motor rpm jumping up and down?

    I desoldered the potentiometer and cleaned it in isopropanol. It looks semi closed, but the isopropanol is so thin and volatile, I guess some of it made it onto the wiper. I also measured it from 0 at one end to 24.4k at the other (I thought it was supposed to be 22k?). I don’t know if leftover carbon residue inside will make the rpm jump, or if there is something else? 

    Any thoughts about this?

  • Thermomix TM31 motor RPM jumping 2

    fixbear

    Member
    January 12, 2020 at 2:16 pm

    Is this a DC motor?  If so check the brushes.  If it has ball bearings,  De-power and manually turn it feeling for a rough bearing or friction change.  Mechanical friction can also be in what it drives.

  • Thermomix TM31 motor RPM jumping 2

    okwestern

    Member
    January 12, 2020 at 4:15 pm

    It’s brushless. And the bearings are good. I’ve manually turned it and it is like butter.

    • Thermomix TM31 motor RPM jumping 2

      fixbear

      Member
      January 13, 2020 at 12:11 pm

      Just wondering if you connected a ohm meter to the pot and watched it as you turn the dial. Any variation of a smooth transition from the min to the max means trouble.

    • Thermomix TM31 motor RPM jumping 2

      fixbear

      Member
      January 13, 2020 at 12:19 pm

      Also does the motor have a hall effect sensing on it. I’ve seen where metallic dust particles have accumulated on the pick up and caused intermittent speed errors.  And of course wiring and connectors.

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