Rapido N Scale TurboTrain Shorting on Reverse Module

Donstaff Jul 20, 2021

  1. Donstaff

    Donstaff TrainBoard Member

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    I have a Rapido N scale TurboTrain with DCC that shorts if it triggers the MRC A520 reversing module section of the wye on my layout. This only happens when the train must trigger the module. If the module is already aligned with the proper polarity, the Turbo goes through with no problem. Also, none of my other DCC locomotives, single or in consist, have problems with the reversing section. Is this because the TurboTrain has an engine with a decoder on each end? And if that is the case, would I have the same problem with a helper on the tail end. Is there a work-around?
     
  2. CSX Robert

    CSX Robert TrainBoard Member

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    Is the train longer than your reverse section? I believe the TurboTrain has electrical connections between all of the cars, and if so it cannot cross the two ends of the reversing section at the same time.
     
  3. Donstaff

    Donstaff TrainBoard Member

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    That is what I believe to be the case too. So, bottom line, you can't use the Rapido TurboTrain on a reverse loop unless a. The loop is already set up not to require triggering, or b. You manually trigger the reversing module so as to set the polarity up not to require a polarity switch?

    How about the DCC Specialist PSX-AR? How would it handle the situation?
     
  4. CSX Robert

    CSX Robert TrainBoard Member

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    You did not answer the question about whether or not the train is longer than the reversing section. If it is, then it will be bridging the track at both ends at the same time, causing a short that no reverser can resolve, not even a manual toggle switch. In that case, the only solution is to either shorten the train or re-work your reversing section to make it longer.
     
  5. acptulsa

    acptulsa TrainBoard Member

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    There's a decoder at each end? It's a hardware problem. Disconnect the wire connecting the two ends, and m.u. them instead.

    I believe my solution would even fix this, unless some of the power pick up wheels at each end are on the reversing section at the same time. But I don't think that's a problem, because he said it only shorts when it triggers reverse.
     
    Last edited: Jul 21, 2021
  6. Donstaff

    Donstaff TrainBoard Member

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    Actually, there IS NOT a decoder at each end. There is a locomotive at each end with three lighted cars in-between. The decoder is is smack dab in the center car of the five-car train. The five-car train is SHORTER than the reversing section. And finally, all five cars plug together.
     

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  7. acptulsa

    acptulsa TrainBoard Member

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    Model Rectifier says this about those:

    This unit was not primarily
    designed for use with standard locomotives, and will cause a non decoder
    equipped loco to travel in reverse after passing an insulated gap. When
    this happens, simply change the direction of the loco using the DCC
    command station.


    If one side of an insulated gap is making a DC locomotive go forward and the other side is making it go backwards, seems to me there'll be a short. All mine have at least four electrified axles. The MRC, which is an electro-mechanical relay, seems to be treating the turbo like a D-single-C unit for some reason. It isn't recognizing the decoder.
     
    Last edited: Jul 21, 2021
  8. Donstaff

    Donstaff TrainBoard Member

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    Here is the manual for the Rapido TurboTrain.
     

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  9. CSX Robert

    CSX Robert TrainBoard Member

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    According to the attached file, there IS a decoder in each end car, While it never explicitly states so, there are sections that make it clear that there is. That being said, to the auto-reverser it really doesn't matter, it should appear just a like a really long engine lash-up. Having two sound lcoomotives and lighted passenger cars, the TurboTrain would likely have a significantly higher current draw than a single locomotive, so it is possible that the AD520 is having trouble with that, although it is supposed to be rated for 5 amps. Could you run a lashup of several other locomotives through the reversing section and see if it has any issues? Also a picture or diagram of your track and autoreverser setup might be helpful.
     
    Last edited: Jul 21, 2021
  10. Donstaff

    Donstaff TrainBoard Member

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    Here's a drawing of the layout reversing section.
     

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  11. CSX Robert

    CSX Robert TrainBoard Member

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    Ok, your reversing section has three boundaries, lets call them top left, bottom left, and right. Does the train cause a short at all three boundaries? Which boundaries and traveling in which direction (left to right or right to left) for each boundary does the train short? Also, what turnouts are you using for that wye?

    As an aside, why have the right side boundary to the reversing section? You could have the entire right side of the layout as the reversing section. You asked before about having a helper on the end of the train - as is you could have problems if the train were long enough to cross a left side boundary and the right side boundary at the same time. You could also have problems without a helper with a train with metal wheels. Having the entire right side of the layout as the reversing section would eliminate that potential problem.

    Aside #2: I'm realy not a fan of auto-reversers. Yes, they generally work and they are the goto for many DCC users when they have a reversing section. What I don't like about them is they detect a problem(a short) and fix it, I would much prefer to prevent the problem to begin with when possible. This layout is a good example of why an auto-reverser is often not needed. If you make the entire right side of the layout the reversing section, then anytime you traverse the wye going to or from that part of the layout, the phase for that part has to match the leg of the wye you are traversing. Since you have to throw the turnout on the right of the wye to also match that leg, you could just switch the phase of that section of the layout whenever you throw the turnout. A DPDT toggle might do, if you throw it fast enough, or you could use a latching relay. Depending on what you use to throw the turnout, there are methods to do both at the same time so it's just one thing you have to "throw."
     
  12. acptulsa

    acptulsa TrainBoard Member

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    It's a point-to-loop. When the train is stopped at the terminal end, he has all week to decide which leg of the wye to take, and align the polarity.
     
  13. CSX Robert

    CSX Robert TrainBoard Member

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    I wasn't clear on my point about "throwing it fast enough." The main concern is if you have sound equipped locos on the reversing side of the layout you may not want to interrupt power to them because it can cause the sound to reset.
     
  14. Donstaff

    Donstaff TrainBoard Member

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    GARAGE LAYOUT WITH LOGGING LOOP 10_25_2020 (FLUSH WITH BACK WALL).png Thanks CSX Robert and acptuisa. Lots of good information and advice there.
    FIRST, I should let you know that the drawing that I included shows the layout as it is currently, but does not show the second loop that is in progress on the right side. That second, under construction loop, is shown in this attached picture.
    SECOND, I plan to replace the existing MRC AD520 with a DCC Specialist PSX-ARSC reversing module. There will be a second PSX-ARSC controlling the second loop, which, again, is still under construction.
    THIRD, the insulated rail liners on the right side of my first drawing were put in to make it possible to break the second reversing loop, the yard, the middle (wye), and the left side into separate blocks by adding two DCC Specialists PSX-1 block controls.
    FINALLY, my thought with use of the PSX-ARSC units wired for auto-reversers was that it would allow me to (a.) Occasionally, run an un-attended train, and (b.) choose whether to go through the loops left-to-right or right-to-left during switching operations.
    I still have not yet tried running a consist through the reversing loop.
     
  15. acptulsa

    acptulsa TrainBoard Member

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    That could conceivably eliminate the problem. MRC says, in the event the locomotive is going forward until it hits the reversing section, then backs up (which should produce a short), When this happens, simply change the direction of the loco using the DCC command station. If you try that and it works, then replacing the AD-520 should fix the problem.
     
  16. CSX Robert

    CSX Robert TrainBoard Member

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    Ok, that does complicate thigns. I can still see how to wire that without auto-reversers, but you mention running a train un-attended. That would require additional sensors and circuitry that would not be needed with the PSX-ARSC's ability to throw turnouts.

    The reason I was wanting to know which boundaries and in which directions the problems are occuring, as well as the type of turnouts, is I'm wondering if you could be getting intermittent shorts on one of the turnouts. If so, they could be brief enough to not be causing any issue normally, but having the TurboTrain bridging a reversing section boundary and the turnout at the same causes issues.
     
  17. acptulsa

    acptulsa TrainBoard Member

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    I have mixed feelings about that. I'm not seeing how that happens only when the reverser triggers, but just because I haven't figured that part out doesn't mean much. Usually intermittent problems only really effect units without flywheels, which this has, although they're really small.

    But there's one reason I see real promise in this idea. Most trains put pressure on the inside rail of a curve, but when a train has pusher power, it can press on the outside rail and bring to light issues other trains don't trigger.
     
  18. Donstaff

    Donstaff TrainBoard Member

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    NOTE: I'm re-posting my previous comment that had the accompanying drawing which included the loop that is under construction. In the original submission, my first two commends were not included. I'm also including the drawing again for convenience.

    Thanks CSX Robert and acptuisa. Lots of good information and advice there.
    FIRST, I should let you know that the drawing that I included shows the layout as it is currently, but does not show the second loop that is in progress on the right side. That second, under construction loop, is shown in this attached picture.
    SECOND, I plan to replace the existing MRC AD520 with a DCC Specialist PSX-ARSC reversing module. There will be a second PSX-ARSC controlling the second loop, which, again, is still under construction.
    THIRD, the insulated rail liners on the right side of my first drawing were put in to make it possible to break the second reversing loop, the yard, the middle (wye), and the left side into separate blocks by adding two DCC Specialists PSX-1 block controls.
    FINALLY, my thought with use of the PSX-ARSC units wired for auto-reversers was that it would allow me to (a.) Occasionally, run an un-attended train, and (b.) choose whether to go through the loops left-to-right or right-to-left during switching operations.
    I still have not yet tried running a consist through the reversing loop.
     

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  19. BigJake

    BigJake TrainBoard Member

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    Okay, I've only skimmed the following posts, but this picture appears to expose the problem.

    The drop you added is apparently shorting out the AR section only when the AR device attempts to reverse the section's polarity relative to the command station. This indicates a short between the command station (or non-reversing booster, circuit breaker, etc.) bus and the AR bus.

    This would happen if that new drop is sourced by either the command station or a non-reversing circuit breaker, booster, etc.

    Ensure that the new drop is powered from the AR device outputs (just like any other drops in that reversing section between insulated gaps).

    Hope this helps...
     
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  20. Donstaff

    Donstaff TrainBoard Member

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    The drop that is marked as "drop that was added before problem started" (re: Train Board Image 070319.png) connects only to the reversing section yellow wires from the MRC AD520, as do all of the connections between the four insulated rail joiners to the left of the wye and the two insulated rail joiners on the right end of the bridge that accesses the yard. The reversing section containing the wye connects to nothing but the yellow AD520 leads. The red AS520 leads connect to the power bus.
     

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