Problems with a GP40-2

SVRailroader Dec 2, 2018

  1. SVRailroader

    SVRailroader TrainBoard Member

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    One of my engines, an Atlas GP40-2, recently developed an interesting problem. When I apply power in DCC, the engine will move; however, after a few seconds (up to about 10), it will then stop. Usually it will resume moving if I adjust the throttle again, although sometimes it takes a second. The lights always remain on if activated. Sometimes I can keep it moving with constant throttle adjustments, but it will still try to slow down on occasion.

    I've had this engine for a while now; probably at least eight years. For most of that time, and still now, it has been equipped with a personally installed TCS AMD4 decoder. This problem only came up a couple months ago, and since I've been building a layout I haven't touched it in most of that time. The problem also seems to be happening in DC mode. My DCC system is a Digitrax Zephyr Xtra. Does anyone have any ideas what might be the problem or solution?
     
  2. MK

    MK TrainBoard Member

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    Are the wheels clean? After 8 years of running (I don't know how much run time it has seen) the nickel plating of the wheels may have worn off exposing the brass. Brass tarnishes and picks up dirt quite easily.

    The only other thing I can think of is the motor contacts to the decoder have shifted and now the contact is not so good.
     
  3. gatrhumpy

    gatrhumpy TrainBoard Member

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    Check continuity between the track and pickup tabs on the decoder. There might be a problem. Also clean the wheels and track to see if that makes a difference.
     
  4. Dogwood

    Dogwood TrainBoard Member

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    Clean all contacts! Even the decoder. Is the gearbox hardened with old grease?
     
  5. SVRailroader

    SVRailroader TrainBoard Member

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    I went and cleaned the wheels and contact strips. The problem continues.

    This time I timed the problem. At about 2/3 throttle, the engine moved for about eight seconds, then stopped for eight. Without me touching the throttle, it then resumed moving for 8, and stopped for 16 seconds. Then another 8 seconds motion and 16 seconds stopped. The lights remained on the whole time.

    I’m starting to think it’s a decoder issue, but I don’t know what might cause that.
     
  6. MK

    MK TrainBoard Member

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    Try resetting the decoder. Write a 2 into CV8. Take it off power, then try again on the main track.
     
    mtntrainman likes this.
  7. tehachapifan

    tehachapifan TrainBoard Member

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    My guess would be the motor contacts are making spotty contact with the pads on the bottom of the decoder....assuming you didn't solder jumpers there.
     
  8. Dogwood

    Dogwood TrainBoard Member

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    Do you've two throttle? When using two hand controllers (DT400 or other), the locomotive can only be placed on one of the two throttle. In this case, delete the address from one of the controls.
    Would be synonymous conceivable.
     
    mtntrainman likes this.
  9. SVRailroader

    SVRailroader TrainBoard Member

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    Looks like Dogwood has the right solution, though it took a moment because I don’t normally use extra throttles. However, the Zephyr is equipped with jump ports to allow the use of DC throttles as DCC controllers. I hadn’t deselected the engine from those throttles last time I used them. Which explains the 8/16 pattern; 8 seconds per throttle with the address. Once I switched the unconnected jump packs to an unused address, all was fixed. So let’s hope I don’t go buy an engine 3000 for a bit.
     
    mtntrainman likes this.
  10. Dogwood

    Dogwood TrainBoard Member

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    I'm using a DIGITRAX Zephyr with the DIGITRAX DT400. Therefore, this scenario seemed familiar to me. But, nice to hear that you now have a positive solution.
    Happy railroading
     
    mtntrainman likes this.
  11. Dogwood

    Dogwood TrainBoard Member

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    And one more hint:

    Delete all temporary loco adresses in your system. Read the discription of your DIGITRAX control. Option switches-clearing system
    Then the memory is empty.
     
    mtntrainman likes this.

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