I have a modest sized shelf layout (9'X20' room, 3' shelf at perimeter) that I ran with an MRC Command 2000 DCC system. The layout is wired with 14 ga bus wire, broken into 5 isolated blocks, each able to be turned off and on with a toggle switch mounted to the layout's facia. Everything ran quite well with the Command 2000. Now I have a Prodigy Express connected to the layout (I'm borrowing it from another's layout) I have the main outputs of the Prodigy connected to my bus wires, but nothing connected to the program outputs (I'm trying out the Prodigy, not programming any decoders). It appears that at two particular locations on the layout, when a large locomotive (an Athearn Genesis Challenger) crosses that point, it sets off the "SVDA" message on the handset (indicating a short). The frustrating part is that it doesn't happen all the time, and there appears to be no real reason why it happens sometimes and not other times. I can say that the common part of both locations appears to be that the locomotive crosses a turnout and then isolated rail joiners immediately after the turnout (into the next block) at both locations. I have plenty of other locations where the locomotive crosses either isolated rail joiners or a turnout with no issue, but not both. The odd part is that this problem also seems to occur (sometimes) with a pair of Athearn RTR 35' Hoper cars (with metal wheelsets) coupled together (ironically, it doesn't happen to each of them separately). I cannot get it to replicate this problem consistenly either, but it's in the same locations. I'll also add that all of my track is Atlas code 83. The switches are either snap switches, #4, or #6 turnouts. All other track is flex track. Additionaly, I don't use any type of circuit breaker, but the Prodigy is wired directly to the bus wire, which is connected to each of the 5 switches serving the 5 block areas. I'm entertaining purchasing a Prodigy (Either Advance2 or Express) and want to make sure I don't spend hundreds of dollars for problems that I can't find or fix. Thanks for your help.
Thanks for asking. My layout generally has 24" or larger curves, and I have used the smaller switches mostly for yards and small sidings to tighten up their length to get more straight track for rail car storage. My layout (when it has scenery) will be set in the 1980's. I currently run nothing longer than 54' hopper cars, and I currently have only 4-axle diesel (GP) locomotives (I do plan to use 6-axle locomotives as well). The Challenger is not mine, but it is also here temporarily (It's kind of a long story, so I won't get into it on the forum). I will say this about the Challenger though - Athearn's literature indicates that (believe it or not) it can run on as tight as 18" radius. Its owner doesn't do that, but it does run on 24" radius quite well. This whole discussion raises another question: I've entertained switching to metal wheel sets on all of my rolling stock. In light of this issue, is that a bad idea and should I use all plastic?
This is just a guess.
Looking at what has changed - it is likely the Prodigy Express is detecting momentary shorts quicker than the Command 2000. You didn't say whether the Challenger ran without problem before, but I'm assuming it did.
Momentary shorts at insulated frogs are known to happen occasionally with Peco Insulfrog turnouts. Back before Pecos were in common use, the same thing would happen on occasion with Atlas turnouts, particularly #6's. I'm not sure the problem carried over to the code 83 and later versions of the Atlas turnouts.
What happens is a metal wheel spans the 2 rails that form the frog point, where they first become "live". The 2 rails are of opposite polarity, and are quite close to each other. This only happens momentarily, as the momentum of the train carries the wheel past the point where it can short. In your case, I suspect the Commander did not trip before the short disappeared, but the Prodidgy Express does register the momentary short circuit.
My suspicions are reinforced by your statements that it only happens at 2 turnouts, and only with particular wheels, and then not all the time.
To test/temporaily fix, coat the first 1/2" of live rail beyond each frog point with nail polish. Only do this to the 2 offending turnouts. Allow to dry and test. If I'm wrong, remove the nail polish, and no harm is done. If I'm right, you will have to recoat the nail polish occasionally or remove some of the rail head on the inside of the frog point so that the wheels can't short across the 2 rails. I would also check the wheel gauging with an NMRA gauge - chances are the offending wheels will also be slightly wide in gauge.
HTH
Fred W
Jeff But it's a dry heat!
I have the Prodigy Express and ran into the same problem with a Spectrum Light Mountain going over Atlas TruTrack turn-outs. These turn-outs are just Code 83 Snap Track.
There is a section on the MRC web-site that explains that the Express is sensitive to slight shorts as it is only 1.6 amps. I sent mine in for an up-grade that they offer to increase it to 2.5 amps at a cost of $25. In fact it came back with a 3.5 amp power supply.
I also changed to Kato UniTrack and since then, no problems. I changed the track as I wasn't very impressed with the quality of the Atlas track and realized that without good track, running trains could be very frustrating.
I like the Express unit as it is easy to use, is a handheld, and find it more than adequate on my small layout. Not to mention that the price was very good.
Do not give up on the express I beleive it is doing its job. I have the Express & the Advavce Squared & love them, they are so easy to use. I to had a similar problem on some turn out's. I put fingernail polish on the frog but still had trouble. Upon looking closely when the short happened I discovereed that the problem was oppisite the frog. Comeing from the rail side to the frog one set of wheel's got to the frog side & one set hit the oposeing rail before the frog. I put fingernail polish on the side of one rail & solved the problem.
Larry
mrgstrain wrote: Do not give up on the express I beleive it is doing its job. I have the Express & the Advavce Squared & love them, they are so easy to use. I to had a similar problem on some turn out's. I put fingernail polish on the frog but still had trouble. Upon looking closely when the short happened I discovereed that the problem was oppisite the frog. Comeing from the rail side to the frog one set of wheel's got to the frog side & one set hit the oposeing rail before the frog. I put fingernail polish on the side of one rail & solved the problem.Larry
This is true, I hope I did not imply otherwise. The problem is not that the PE is sensing the short, it is the fact that there is a short. The PE is a fairly low power system, and is from the evidence is more sensitive to shorts than some systems, but it is not the problem.
I had the same problem when I first got my PE. For some reason when I tried to cross over my parallel tracks I would get the "SVDA" code. I was using old (Approx 10 15 years) Atlas Turnouts. I replacedc the TO's where there was a problem with new Atlas TO's and there was no more prblem. I'm no expert, but Once you change over to DCC you may want to get rid of the blocks. It may cause more shorts.
Smitty
smitty311 wrote: I had the same problem when I first got my PE. For some reason when I tried to cross over my parallel tracks I would get the "SVDA" code. I was using old (Approx 10 15 years) Atlas Turnouts. I replacedc the TO's where there was a problem with new Atlas TO's and there was no more prblem. I'm no expert, but Once you change over to DCC you may want to get rid of the blocks. It may cause more shorts.Smitty
No need to get rid of blocks, blocks don't cause shorts. In a DC system you can get away with quick shorts, and everything keeps working. Because of the nature of DCC it is less tolerant of shorts, so shorts that were tolerable, or perhaps not even none about, in DC become a problem. And, as is seen in this instance, different DCC systems can be more or less tolerant.