Just wanted to update this thread. At first, I was leaning toward the Digitrax AR-1 but when I realized it too has a mechanical switch, I decided to spend a few bucks more and get the PSX-AR. I received it in the mail today, along with the latest issue of MR. I opened the box immediately and was relieved that the hook up seemed to be fairly simple. Just two wires in and two wires out, just like the MRC AR. The only difference was it didn't come pre-wired. No big deal. I've got plenty of spare wire and selected 18 gauge for connecting to the bus wires. It took just a few minutes to unhook the MRC and swap in the PSX-AR. I ran my first test, anxiously watching as the first engine approached the insulating gaps. It barfed!!! I was beside myself. I went around all the reverse loop wiring looking for problem with the wiring and could find nothing. Then I took another look at the loco. It was a F7 A/B lashup and the B unit was over the turnout frog just as the A unit hit the insulating gaps. It was then I noticed the B unit was not on rails properly and apparently shorted out when the derailed wheels hit the frog. I corrected that problem and PRESTO!!! Ran it back and forth over both ends of the loop. Worked perfectly every time. What a relief to be able to operate both loops flawlessly.
I am still puzzled by the MRC because it continued to work perfectly on the upper loop but got continually worse performance on the lower loop until it had reached a point where it was failing almost every time. I have no idea why that would be. If the problem was in the unit itself, you would think it would fail on both loops, not just the one. On the other hand, if the bad loop was wired incorrectly, why did installing the PSX-AR fix it. Since the MRC is apparently toast, I am going to cut open the vinyl covering and see if I can see anything wrong with it. In any case, it's great to be able to operate the whole layout again.
Well, I think I've got it worked out. I replaced the long feeder wires running to the reverser with heavier bus wires (14 gauge) and then soddered shorter feeder wires to the the bus at various points around the loop. At first, I noticed only a slight improvement. The shutdowns were less frequent, but still happening too often to be acceptable. Then I notice a loose sodder connection between the feeder wire and the rail near the throat of the problem reverse loop. I resoddered the wire and everything started to work just like it was supposed to. I made dozens of entries and exits in the problem loop and alternated that with entries and exits to the good loop so I would get lots of polarity changes. I only got two shutdowns and those both occurred when I exited the problem loop in the opposite direction from how trains will enter the loop during operations. I was also running the loco over the gaps faster than I would have in normal operations so that my have contributed to the shutdown.
Now I can't be sure if the problem was the lack of a bus wire for the loop or the loose connection to the rail. It doesn't really matter since both have been remedied. I suppose it is possible that when I soddered the feeder wire to the bus, I worked it loose from the rail, but I'll never know that for sure. In any case, I believe I've fixed the problem and in the process have increased my understanding of the electronics involved in the auto reversers.
Thanks to all who helped me work through this problem.
John
Take a look at: Allan Gartner's Turnout DCC Page and especially Tony's Train Exchange on Long Reverse Loops in DCC
Alan
Co-owner of the proposed CT River Valley RR (HO scale) http://home.comcast.net/~docinct/CTRiverValleyRR/
Vail and Southwestern RR jecorbett The other possibility I thought of is that the feeder wires from the problem loop to the auto reverser are longer than the ones from the good loop. Could this cause a lack of signal strength which could also prevent the reverser from doing its job. I think my feeder wires are either 20 or 22 gauge. It's been a while since they were installed so I can't remember for sure. My bus wires are 14 gauge. This is what I tried to suggest yesterday. Do the feeder wires go all the way back to the reverser? Or do you run a sub bus from the reverser, and then drop several sets of feeders to the rails? How long are these feeders? The reverse loops should be wired pretty much the same way as the main, with a bus and feeders, with the bus being fed from the output of the reverser. If you ran the feeders all the way to the reverser, and the distance is more than a few feet, I think you may have discovered your problem.
jecorbett The other possibility I thought of is that the feeder wires from the problem loop to the auto reverser are longer than the ones from the good loop. Could this cause a lack of signal strength which could also prevent the reverser from doing its job. I think my feeder wires are either 20 or 22 gauge. It's been a while since they were installed so I can't remember for sure. My bus wires are 14 gauge.
This is what I tried to suggest yesterday. Do the feeder wires go all the way back to the reverser? Or do you run a sub bus from the reverser, and then drop several sets of feeders to the rails? How long are these feeders? The reverse loops should be wired pretty much the same way as the main, with a bus and feeders, with the bus being fed from the output of the reverser. If you ran the feeders all the way to the reverser, and the distance is more than a few feet, I think you may have discovered your problem.
Okay, I must have misunderstood what you had suggested earlier. The feeder wires do go from several points on the loops to a Miniatronics terminal strip that is connected to the reverser. The feeders at the throat of the problem loop are the furthest ones from the terminal strip. I'd estimate 6 feet or more while the throat of the good loop is just a couple feet from the terminals strip. If I understand what you are suggesting, I should have the same heavy gauge bus wires around the loops that I have for the main line and I should attach short feeders to the bus from the various points around the loop. Sounds like a plan. I'll give this a shot and see how it goes. Thanks for the suggestion.
Jeff But it's a dry heat!
cacole Just today, I went to help a friend with his HO scale layout because his EasyDCC was continually reporting a short circuit even though no changes at all had been made to his layout. By crawling underneath and tracing the track buss wiring one terminal block at a time, disconnecting wires and then reconnecting them when it never eliminated the short, I eventually found that one of his Digitrax AR-1 modules had, for reasons unknown, suddenly shorted out. Don't know if it is a stuck relay or what, but every time it is connected it causes a short. He's going to change to a DCC Specialties On Guard solid-state auto-reverse module. No mechanical relay to go bad. So yes, Digitrax AR-1 auto reverse modules can go bad for no apparent reason, and this may be what has happened to yours.
Just today, I went to help a friend with his HO scale layout because his EasyDCC was continually reporting a short circuit even though no changes at all had been made to his layout.
By crawling underneath and tracing the track buss wiring one terminal block at a time, disconnecting wires and then reconnecting them when it never eliminated the short, I eventually found that one of his Digitrax AR-1 modules had, for reasons unknown, suddenly shorted out.
Don't know if it is a stuck relay or what, but every time it is connected it causes a short. He's going to change to a DCC Specialties On Guard solid-state auto-reverse module. No mechanical relay to go bad.
So yes, Digitrax AR-1 auto reverse modules can go bad for no apparent reason, and this may be what has happened to yours.
I won't rule out that the auto reverser has gone bad, but that would make more sense if it happened on both loops instead of just the one.
After watching my Huskers give away a game for the third time this season, I was too upset to go straight to bed so I decided to spend some late night time in the train room to try and make me forget (it didn't work).
Here is what I learned during the latest session. The problem has gone back to being sporadic. Sometimes it happens, sometimes it doesn't. Secondly, whether I get the shut down or not has nothing to do with which way I have the feeders running from the the reverser to the bus wires. It depends on which direction the last locomotive to enter or exit the good loop was traveling. Logically, my railroad runs east/west. The loop that doesn't have the problems is on the west end, so when a train enters that loop, it is traveling in a westbound direction and the auto reverser sets the both reversing sections to match westbound polarity on the main section. That means if I the next loco enters the east end loop, the direction of travel will be eastbound which does not match the polarity of loop which is still set for westbound, and if the auto reverser doesn't do its job, the loco will be bridging two sections with opposing polarity. However, if I have just exited a loco from the west end loop, it will be traveling in an eastbound direction and the both reversing sections will be set to match the polarity of an eastbound train. That allows me to enter the east end loop without a problem but instead I get the short when the loco tries to pass from the loop onto the westbound main with the loop set for easbound polarity, unless the reverser does its job and instantly flips the reversing section polarity to match the westbound direction of the main. The problem is, sometimes it does, and sometimes it doesn't, but why is that only a problem on one of the two loops. I can think of two possible reasons and maybe someone who is a little more electrically saavy than me can tell me if either makes sense. If the track on the problem loop were not as clear as on the other loop, could it be that the auto reverser is not getting a strong enough signal from it to allow it to reverse the polarity before the DCC system detects a short? The other possibility I thought of is that the feeder wires from the problem loop to the auto reverser are longer than the ones from the good loop. Could this cause a lack of signal strength which could also prevent the reverser from doing its job. I think my feeder wires are either 20 or 22 gauge. It's been a while since they were installed so I can't remember for sure. My bus wires are 14 gauge.
Well that's where things stand now. It's now past 1:00 am so I'm going to try to get some sleep. It's going to be tough though. I'll keep seeing that kickoff going out of bounds setting Texas up for the game winning field goal.
jecorbettI am curious about the suggestion to stagger the insulated rail joiners about 1/8 inch. What could this do for me if I try it?
I am curious about the suggestion to stagger the insulated rail joiners about 1/8 inch. What could this do for me if I try it?
If the gaps are exactly opposite so that metal wheels on both sides of the engine cross the gaps at almost exactly the same instant, the autoreverser can get confused by detecting the 2nd short before it can flip the polarity from the 1st short. The staggering prevents the 2nd wheel from crossing the gap before the polarity has been flipped. But you don't want the staggering long enough that a 2nd wheel in the truck could be hitting the gap at the same as the 1st wheel on the opposite side, either. Hence the 1/8" recommendation, as that is shorter than the wheelbase of any 2 adjoining wheel sets.
Fred W
This is starting to remind me of my days as a programmer of main frame computers. You are trying to debug a problem that seems illogical and you start to swear it is a computer problem even though your experience tells you it is never a computer problem. It is a programming problem. The computer never makes a mistake. It always does exactly what it is told to do. The problem is always a programming problem. It is usually something you never even considered. Something where you assumed something that turned out to be an invalid assumption. At this point, I am thinking of getting a seperate reverser for the problem loop. That will at least tell me whether it is a problem with the reverser or some other problem. Please keep the suggestions coming. You never know when you are going to hit on the real problem.
Perhaps I was wrong. It does sound like it is not reversing when the engine hits the transition joint. I must now agree with the poster who said the reverser needs the sensitivity adjusted if that is possible with your particular reverser. Another possibility is that the reverser is failing but that would seem to not be the case if it still works on the other loop.
I presume that you have nothing new on the layout that interferes with it.
Dave
Lackawanna Route of the Phoebe Snow
I had a brief break between the Cincinnati-Pitt game (WOW what a game, Cincy 45, Pitt 44) and the SEC championship game, the game of the year. I gave the track a thorough cleaning and then ran a loco over the insulated gap between the main section and the reversing section at a creeping speed. I can tell you that the loco exiting the reversing section onto the main section cause a short the instant the front wheels hit the main section. I'm talking about the front wheels of the front truck causing the short. The back wheels of the front truck never reached the main section. The insulated rail joiners are at the point end of the turnout which form both the entrance and exit to reversing loops. The short occurs the instant those front wheels cross the insulated rail joiners from the one section to the other.
I am curious about the suggestion to stagger the insulated rail joiners about 1/8 inch. I'm willing to try about anything at this point but this will involve ripping up some ballasted track and laying it over again with the gaps moved. What could this do for me if I try it?
Both loops are controlled by the same reverser. The short does not occur when the reverser is tripped at the other end of the layout. Therefore the polarity reversing on the offending loop is not causing the short. The short must be occurring when the joint is bridged by the engine at the offending point.
You have not supplied a diagram. Can we assume that the loop is between two legs of a switch? If so, look for a problem at the frog or points of that switch. Check to see if the back side of the metal wheel of the engine is shorting somewhere in the switch.
Some great ideas so far. At least I have some things to try and gets me off the dead end I am at now. At worst, I can eliminate some possible reasons for the problem and maybe one of these will turn out to be the problem. PhoebeVet, you seem to have a firm grasp of the problem and you are thinking along the same lines as I am. David, your mention of dirty track really grabbed my attention. Dirty track is a distinct possibility since I haven't run the railroad for a while. Although this wouldn't explain why the problem area changed when I reversed the feeder wires from the bus to the reverser, if both sections were dirty, the one section would be OK if it matched the main section polarity and the one that needed to reverse might not manage to change the polarity until after the Lenz system shut down. It's worth a try. Crandall, I don't think the problem is with the engine because I have been running 4 different locos, two of which are multiple F-units, and I get the same problem with all of them. Good suggestions from all anyway. They all gave me a new way to look at the problem and that is a big help.
At least now, I have several ideas to try out. However, since this is Championship Saturday, I am as big a college football fan as I am a railroad buff, and I have followed the Huskers since the early 1960s and this is the first center ring game we've played in a long time, I will be in front of the TV all day and all night. The Huskers aren't going to play for the national championship but we could have say in who does. I give us a puncher's chance. Right now Cincinnati and Pittsburgh are playing a very entertaining game and since I don't really care who wins this one, I can sit back and enjoy. Tonight, I'll be on pins and needles. I live and die with Husker football.
If I understand your description you have 4 transition locations in 2 loops controlled by a single reverser and you have not changed anything since it used to work. If it now shorts at only one transition location, always the same location and regardless of direction of travel then the problem HAS to be at that transition location. Something is causing the reversal of polarity at that location to cause a short.
Check the polarity through the switch. Run the engine or a lighted car very slowly through the transition location in both directions and see exactly where the wheels are when it shorts. Does the short occur when it reverses, or shortly thereafter?
The reverser must be OK or it would short at all 4 transition locations.
John, I can only come up with two possibilities: engine is getting old and some conditions cause bare metal that shouldn't to come into contact with other bare metal and you get the short, or the reverser is toast.
Care to guess which way I'm leaning?
-Crandell
Is anything bridging any of the gaps, other than the one point where you are having the problem? The auto-reverser is going to flip the polarity on both loops, the way you have it wired, so the other 3 gaps must be clear, not just the gap at the other end of the active loop.
Since you said it's a "long dogbone" layout, I assume you've got a set of bus lines for the auto-reverse circuits running to each end. Try disconnecting the end that's not having problems, and see if that fixes it.
Finally, check all your wiring. If you've got a single feeder from the main line accidentally connected to a track in the auto-reverse zone, you would see a problem like this. From the intermittent nature of this problem, I'd imagine that one siding has such a wiring error. That siding is fed by a power-routing turnout, which is not making good contact. With the turnout in one position, all is well, but if it's thrown the other way, then the quality of the point contact decides whether your circuit will work or not.
It takes an iron man to play with a toy iron horse.
Does this reverse module have a sensitivity adjustment of any type? I'm not sure, but some auto reversers used mechanical relays and could be adjusted with a potentiometer.
If all else fails. change to an all electronic module such as the PS-REV from Tony's Train Exchange.
One thing that Tony recommends with the PS-REV is that the insulated rail joints at both ends of the reversing section be staggered by about 1/8 inch. Doing this may solve your problem with the MRC module.
I've gotten some good help here the last couple weeks on several problems and hope I can again with my latest problem. First a little background. I went through an extended period where the layout was not operating due to some major scenery projects that shut down the main line. Just the past couple weeks I have begun to run trains again and as seems to happen over time, gremlins have found their way onto the layout.
My latest problem involves my MRC auto reverser. I run a DCC system (Lenz 100 if that matters). My layout is a large dogbone with hidden staging yards in the loops. I bought an MRC auto reverser to handle the polarity issue of reversing sections. I use the auto reverser to control both loops and my guru at the LHS told me he thought that would work as long as I didn't have trains entering and exiting the loops simultaneously. Since I am a lone wolf operator, I didn't think that would be an issue and initially it wasn't. I was able to move trains in and out of the loops at both ends of the layout without any concern for polarity. Just the last couple of days, a problem has popped up that has me perplexed. When trains entered the loop at one end of the layout, a short was detected and the Lenz system shut down as it is supposed to do. Initially, it was happening sporadically but now it happens almost every time, but it happens on only one of the loops, not both. My trains always pass through the loops in a counter clockwise direction, so it would happen at the same point everytime. Just to see what would happen, I reversed the wires connecting the auto-reverser to the bus lines. Trains were able to enter the loop but then I got the short when they tried to exit.
If I understand the way the auto-reverser works, polarity on the mainline remains constant, then when a loco passes from the main section to the reversing section and the auto reverser detects conflicting polarity, it instantly changes the polarity to the reversing section so it matches the main section. What seems to me is that the polarity on the one loop is set one way but is not getting flipped quickly enough to prevent a system shutdown. This would explain why reversing the feed wires from the bus to the auto reverser changed the problem spot from the loop entrance to the exit point. I tried backing a loco into the loop so it would go around the loop in a clockwise direction. It shorted when it crossed what is normally the loop exit but was its entrance point when backing into the loop. In other words, it shorted at the same point no matter which direction the loco was moving.
My suspiscion is that the auto reverser might be faulty, but if that were the case, why would it work on one loop but not the other. On the other hand, if I had a bad connection between the auto reverser and the reversing loop, wouldn't that prevent trains from even running on the loop at all.
Any ideas? I'm stumped. Thanks in advance for anyone who has anything to offer.