Athearn SD-70 Can Motor Issue

gatrhumpy Nov 25, 2019

  1. gatrhumpy

    gatrhumpy TrainBoard Member

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    I have an N Scale Athearn SD-70 that has a Mashima motor in it. Randomly, the locomotive will stop, with the lights and sound still on and running (I installed a DCC sound decoder in it). The sound or lights do not go out; the locomotive just stops.

    With the power still applied, I remove the shell, and use a rubber eraser from a pencil to move the flywheels, and the motor seems like it wants to go but it seems like torque is not there to move the gears. I remove the locomotive from the track and move the flywheels, and the gears turn freely. There is no debris or lint holding up the gears in each truck.

    I thought that Mashima motors were good. What's going on? Anyone know how to oil the bearings or internal parts of the motor without actually removing the motor from the frame? The motor is getting power (as proven by the fact that the motor will spin about 1/20th of a full revolution when I use a rubber eraser to turn the flywheel and that I can hear the electrical growl each time I do that), so that tells me it's not a problem with the decoder OR power electrical pickup.
     
  2. bill pearce

    bill pearce TrainBoard Member

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    Perhaps a portion of one of the winding is open or shorted?
     
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  3. Doug Gosha

    Doug Gosha TrainBoard Member

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    Is it new, well used, mildly used? In any event, defects happen or parts wear out or fail.

    Doug
     
  4. gatrhumpy

    gatrhumpy TrainBoard Member

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    Not a short because like I said I can turn the flywheels with a rubber eraser and then I can hear the motor wake up about say 0 degrees and 180 degrees on the rotational axis. I don't hear a shorting "sound."

    I got it to run for about 35 minutes after I posted the original post and it ran fine without stopping. Not sure what's going on.

    The SD-70 is gently used, perhaps with about 10 hours of run time total.
     
  5. acptulsa

    acptulsa TrainBoard Member

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    Sounds like it's getting power, but not enough. Got a meter you can use to test motor feed output from the DCC?
     
  6. bill pearce

    bill pearce TrainBoard Member

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    If it turns but less that a ful lturn, it's almost gotta be an open winding.
     
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  7. catfan

    catfan TrainBoard Member

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    What generation of Athearn SD-70 are we looking at? 5 pole or 3 pole motor?
     
  8. Hardcoaler

    Hardcoaler TrainBoard Member

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    My vote is with Bill. If the motor stops with a pole contacting a brush and the pole has its feed wire broken or intermittently making contact, the motor won't turn. By helping it turn away from that pole toward the next one by turning the armature with a pencil eraser, the motor will start and run. With the motor running and flywheels spinning, the presence of a dead or intermittent pole will hardly be noticed if at all, especially with a 5-Poler.
     
  9. catfan

    catfan TrainBoard Member

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  10. Hardcoaler

    Hardcoaler TrainBoard Member

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    Good heavens regarding all of the internal variations with this model! o_O Reads as if Athearn finally got it right in the end.
     

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