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Thermomix TM31 motor RPM jumping
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?
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4 Replies
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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.
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It’s brushless. And the bearings are good. I’ve manually turned it and it is like butter.
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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.
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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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