Decoder installed - now the shell won't go back on!

Many Trains Sep 3, 2021

  1. Many Trains

    Many Trains TrainBoard Member

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    This might be a DCC question, but since it's n-scale, I'll put it here.

    I installed a drop in decoder (NCE N12A2) in an Atlas GP7. Motor runs fine, very happy in fact - a nice change as the drops in don't always work so well getting those stupid motor tabs to make good contact with the decoder. So all seems well, a quick install, runs great.

    Uh oh - now the shell won't go on. I can BARELY squeeze the thing on, and it won't go all the way down. It looks like there is a slight bulge in the middle now - the area on the shell above where the fuel tank would be.

    The motor frame does not look like it could possibly go together any tighter. There are no gaps between the decoder board and the frame. Nothing obvious that I can see.

    Any suggestions?

    Interestingly, this has happened to me before, and always with the GP7/9 models. I've not been able to solve this.
     
  2. MK

    MK TrainBoard Member

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    There is a black motor "frame" that the motor is held in. There are 8 little tabs on the corners, 4 on each side. Make sure those tabs are in on each metal half frames. If they are not aligned right, the two frames won't come in close enough to each other and your shell won't go on.

    If you can posts some pictures they may give us some hints on to what's going on.
     
  3. Many Trains

    Many Trains TrainBoard Member

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    I only see 4 tabs, two on each side at the top. They are all in, none sticking out.
     
  4. JMaurer1

    JMaurer1 TrainBoard Member

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    Two words: bigger hammer :)
     
    mtntrainman and Many Trains like this.
  5. JBrown

    JBrown TrainBoard Member

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    Should be two at the bottom on both sides...
     
  6. Many Trains

    Many Trains TrainBoard Member

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    I see them now. I took the fuel tank off and found them. Similar to the ones at the top, they are also not sticking out.
     
  7. Many Trains

    Many Trains TrainBoard Member

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    Believe me, I am tempted! There are times when it's so frustrating, smashing it to pieces seems like a better plan than trying to fix it. :(
     
  8. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

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    Did you put the little contact clips onto the decoder that are on the standard light board (that go into the slots where the boards make contact with the frame)? Sometimes, decoders are just a bit thicker, so won't slide all the way in if the clips are on.
     
  9. JBrown

    JBrown TrainBoard Member

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    Photo's would help.
     
    SP-Wolf likes this.
  10. Many Trains

    Many Trains TrainBoard Member

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    No - no contact clips. I haven't actually seen a decoder with these in quite a while.

    I tried two different decoders to see if that would make a difference, one of them an older NCE (that still has the bulb for a light instead of LED) and the other a TCS decoder. Neither would allow the shell on.

    I then tried the older NCE decoder in a different GP7 frame and viola, it worked! I tried the first decoder (the new NCE that i used to start all this) in a different frame and got the same result, the shell will not go on.

    I'll see if I can get some photos.
     
  11. acptulsa

    acptulsa TrainBoard Member

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    You're going at it backwards. Try putting the locomotive inside something electronic.

    [​IMG]

    Go old school enough and it'll fit easily.

    Hey, trains in vacuum tubes work for Elon Musk.
     
    digimar52, Shortround and freddy_fo like this.
  12. Sumner

    Sumner TrainBoard Member

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    Are you positive they aren't holding the two frame half's slightly apart at the bottom since that is where the shell binds?

    Sumner
     
  13. NtheBasement

    NtheBasement TrainBoard Member

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    Sounds like its not the decoder but test that: see if you can get the shell back on with no decoder.
     
  14. urodoji

    urodoji TrainBoard Member

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    Check that the corners of the decoder aren't hanging up inside the shell, or interfering with the light castings.
     

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