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Discussion in 'Sensors and Actuators' started by Ray Beam, May 15, 2016.

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  1. Ray Beam

    Ray Beam

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    May 15, 2016
    I'm trying to troubleshoot an small motor in a sewing machine that after starting will slow down to a halt. Checked electrical contacts, brushes and cables and they all seen ok. The hand crank in the machine turns but it seems to have a sertain amount of resistance. Any other suggestion on further troubleshooting?
     
  2. BobK

    BobK

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    Jan 5, 2010
    The first thing I would try is lubricating it. There should be a small hole(s) in the motor casing for this.

    Bob
     
    shrtrnd likes this.
  3. Minder

    Minder

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    Apr 24, 2015
    Many of the older Universal motor S.M.'s had a variable resistance foot pedal, check or by pass it to test whether the motor or not.
    M.
     
  4. Alec_t

    Alec_t

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    Jul 7, 2015
    I'm with Bob. Running dry involves high friction which creates heat which causes expansion which increases friction which increases heat ......
     
  5. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Your symptom sure seems like the issue with my mom's sewing machine. BobK's on the right track with this.
    When the machine slows down, it's usually mechanical, not electrical. (Though Alec_t has seen this before).
    Good luck. Check the gearing (if there is any), or if rubber belt is ok. Sometimes the gearing on my mom's would
    get gummed up from grime.
     
  6. Bluejets

    Bluejets

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    Oct 5, 2014
    I'm surprised it is not emitting piles of smoke. In the absence of that then I'd go with Minders solution and check the carbon stack control.
     
  7. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    I am with everyone else on this. Sewing machines, like fine old watches, need periodic cleaning and lubricating, including the (usually) oilite bearings in the motor. Find the owner's manual for instructions on how.
     
  8. Ray Beam

    Ray Beam

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    0
    May 15, 2016
    Thanks you fellows for your recommendations and hints. The problem seems to be friction, the motor brushes are new, a new belt installed and all electrical components passed the test and after flushing the frame with a solvent the unit ran for twice the time it did before slowing down. The next will be to disassemble the main gear and further clean the insides if that is possible. Thanks again for your help.
     
  9. hevans1944

    hevans1944 Hop - AC8NS

    4,547
    2,122
    Jun 21, 2012
    Back in the day, we would dip the whole machine in solvent... after removing all the parts that could be damaged by solvent of course: motor, rubberized belts, spools of thread (don't forget to remove and clean the bobbin under the bottom plate). If you use solvent, test it on non-essential areas of any plastic parts to make sure they don't dissolve. Try to find the owner's manual or a service manual for tips on where to lubricate and what to use for lubricant. Might be some grease as well as oil requirements.

    You might even consider pressure-washing the machine at a coin-operated car wash, followed immediately afterward by thorough drying with soft cloths and in an oven at low temperature, re-lubricating after it cools off. I once visited a Government test equipment storage depot looking for equipment we could "borrow" under an existing Government contract. They had dozens of Tektronix oscilloscope with the covers and vacuum tubes removed that were in a line for passage through a commercial dish washer and dryer. The 'scopes came out spic and span clean. I don't know if they replaced the tubes that were removed or installed new ones, but the final result (after testing and alignment) was a "like new" oscilloscope that performed to original Tektronix specifications. Of course all these 'scopes were obsolete (that's why they had been turned in to the depot), so I ended up saying, "Thank you, but no thank you." I went back to Dayton without a 'scope, but discovered that electronics, even complicated and expensive electronics, could be washed and cleaned with detergent and water then rinsed and warm-air dried. I wonder how a modern lap-top computer would take to that? I have an open motherboard sitting next to this keyboard, and both look like they could use a bath... but if it ain't broke, I ain't gonna fix it. Maybe blow some air from a can on it once in a while though.
     
    Last edited: May 17, 2016
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