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Thread: MM20/SP500 bandsaw, motor dead?

  1. #1
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    MM20/SP500 bandsaw, motor dead?

    I went to start the MM20 today and it was non-functional.

    Single phase 240v setup.

    I started investigating the point of failure and have discovered that:

    -The switch appears to be functional. Each motor lead shows 120v but the motor does not hum when the switch is pressed.

    -The capacitors are good according to my multimeter. For posterity I swapped them to new capacitors and they’re also good.

    I’m now wondering if there is an internal overload that requires taking the motor apart to access but I’m unsure.

    The motor is a 100L frame euro motor made by Motek.

    Resistance across the leads is 0.7 ohms. This seems low compared to other motors I have.

    Resistance to ground from the motor leads both show OL which I believe is s good sign.
    Bumbling forward into the unknown.

  2. #2
    Presuming you've checked both door switches?

  3. #3
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    I’ve got 120v at each lead inside the motor when I push the start button so I’m assuming they are good.

  4. #4
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    If it has a switch like this. Or similar you can find a replacement at https://controlparts.com/
    My went out a couple years ago.
    Good Luck
    Attached Images Attached Images
    Aj

  5. #5
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    I have 120v on all circuits when I press the start button. The button holds and provides 120v to the motor and coils…..yet….nothing happens.

    I’m at a loss as to why it doesn’t hum or try to start or smoke or something, just dead.

  6. #6
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    That’s sure is weird.
    I’m trying to remember my diagnosis before I spoke to a tech.
    His recommendation was remove switch from housing leave all the wires hooked up. Turn it upside down and give it some taps.
    I was able to start my saw. In fact I ran it style swich upside down for a long until I found a replacement.
    I since learned those single phase switches are notorious for failing.
    Good Luck
    Aj

  7. #7
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    All the single phase equipment on this machine is going flying into orbit soon.

  8. #8
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    Are you testing voltage with an electronic meter? You might be seeing phantom voltage from a basically failed connection-- eg voltage but minuscule current capacity. An old-fashioned solenoid type circuit tester is a better choice to ensure what you are seeing is real.

    Switch is still the most likely culprit. If it really has voltage then a trip to the motor shop for testing is probably in order.

  9. #9
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    When I shut the switch off the 120v goes to zero, as it should.

  10. #10
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    Is there a centrifugal start switch in the motor?

  11. #11
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    Spoke with SCM, there are no internal overloads, so he thinks if the motor doesn’t do anything with power supplied that it is dead.

  12. #12
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    Richard, I’m not sure.

  13. #13
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    May be a good idea to have a local motor shop look at it...since all the switches appear to be cooperating and the capacitor(s) are good, probably something in the windings...maybe something came loose internally. Maybe see if Sam Blasco has any ideas, too.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  14. #14
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    Spoke to Sam, he thought it might be the switches.

    Both local motor shops are a booked for a month.

    Between cost of replacement switches, downtime and cost of repair, I decided just to replace it. The single phase motors are a giant headache.

    I bought a Lafert 5.5hp motor and sourcing a hitachi vfd for it.

  15. #15
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    I would test the centrifugal switch like somebody else mentioned. If the centrifugal switch is stuck open then the motor will not be able to generate enough electromagnetic force to overcome inertia to start rotating. If that is the case then it might start with no load if you manually give it a spin but it would be safer to check the centrifugal switch for continuity. The centrifugal switch should be closed during the motor start phase so you should find continuity. If not, then the centrifugal switch is bad or needs to be cleaned out.

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