DCC loco unexpectedly stops and will not respond.

Bill Watts Apr 19, 2020

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  1. Bill Watts

    Bill Watts TrainBoard Member

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    I recently fitted a Lenz standard Plus V2 decoder to a Lima Deltic model. All went well until yesterday when it refused to move at all.

    I am running a DCC++ system based on an Arduino Mega 2560 clone and motor board, using JMRI as the control interface.

    I have put an oscilloscope on the track and the signals appear to be present, I have a peak to peak voltage of approximately 14 v square wave at about 8kHz. pulse modulation can be seen taking place when commands are sent to the track.

    Normal idle current in the circuit with a stationary loco is 40mA, but now the current has dropped to 30mA.

    The carriages I have with lighting are all illuminated normally so power seems to be getting to the track.

    I removed the decoder and bridged the track pickups directly to the motor connections and ran the track on DC and the motor operated as expected in both directions with no problem.

    With the decoder in place and on the programming track When I try to access the CVs I get the error message "No acknowledge from locomotive (308)" and read data returns "Unknown"

    I have changed out the Mega 2560 for a brand new unit, and likewise for the motor board. This has had no effect on the problem.

    As I am building all this from scratch I have no other loco fitted with a decoder to compare results.

    It looks to me like the decoder has failed, I have read that it is possible that the decoder can "lock up" and needs to be reset, and I have the data for that reset process, but JMRI will not allow me to access the CV responsible.

    So the questions are:-

    How exactly do I send a reset code to the decoder from JMRI?

    Is it likely that the decoder has failed?

    Have I missed something obvious?



    Thanks for your assistance in advance
     
  2. wvgca

    wvgca TrainBoard Member

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    308 is usually as error code for the shield board, but you say you changed that ??
    it -may- be possible that the single decoder you have has died, but it's pretty unlikely ..
    more often it's a small change uploaded to the arduino, that's doesn't work properly
     
  3. RCMan

    RCMan TrainBoard Member

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    Try another good running Engine with a decoder on the track, if it works your other decoder is bad or changed the ID#, try factory reset of the decoder then to verify
     
  4. Bill Watts

    Bill Watts TrainBoard Member

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    RC man, as I mentioned in post, I don't have another DCC fitted loco.
     
  5. Bill Watts

    Bill Watts TrainBoard Member

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    WVGCA, no program changes have been made to the Arduino code. It has been soak testing for a week. I think it may be the decoder then
     
  6. Pieter

    Pieter TrainBoard Member

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    CV8 is a non-programmable CV, but will accept a 8 or a 4 (depending on the manufacture specs) for a factory reset. Maybe check your wiring on engine if you spliced it in ( no NEM socket). The black or red wire could have come undone, or wheel whipper could have bend slightly out of place and breaking contact.
     
  7. Bill Watts

    Bill Watts TrainBoard Member

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    Cracked it, thank you all for your assistance. The NEM socket was faulty. It was stopping the plug from going all the way in. Just lucky it had run at all in the first place!
     
  8. acptulsa

    acptulsa TrainBoard Member

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    Am I the only one who thinks of DCC as a way to turn a perfectly good iron horse into a stubborn donkey?
     
  9. Bill Watts

    Bill Watts TrainBoard Member

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    Glass half full?:) I prefer to think of it as a challenge!
     
  10. acptulsa

    acptulsa TrainBoard Member

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    LOL

    My actual problem is I enjoy the challenge of power dispatching (controlling trains by routing power to them) more. I like it. But for some reason, the more of these threads I see, the more tempted I am to gloat. :oops:
     

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