All Power Districts are Shorting Out/Pulsing Even With Track Gaps

Model Railroader Electronics and DCC
1

Hi. I’ve tried to make this request for help as concise as my limited technical/electrical knowledge will allow. My buddy will come over tomorrow (Tues.) to help and bring some spare gear/cables to swap out. So I may not be able to respond with any conviction until then.

He did think it might be the Command Station that’s malfunctioning but all lights seem correct. He pulled some wires from the C.S. hookups and thinks he isolated it but we’ll confirm that when he swaps out with his gear.

Here goes. Thanks for your help!

I have a Super Chief Digitrax system using DT400R throttle.

I have been running without issues for a long time but suddenly, I’m experiencing short circuit indicators on my PSX s and it shuts down BOTH the main and yard. They are on separate busses and power districts are in place via gaps in the tracks.

I’ve trouble shot the layout wiring (and don’t think that’s the issue anyway-all recent, new installation but in use for months to 2 yrs. depending on the section. The only NEW addition was an AR PSX board for a wye. The wye is hand thrown for now so no switch motor involved.

Here are the behaviors I and fellow troubleshooters have seen:

.01 I have three separate power districts. The main yard and the mainline are separately bused (bussed) but there is an additional industrial yard that is only fed via a feeder from the mainlline as we’re about to install that buss. Everything previously seemed to get enough current prior to these problems:

l. For a couple of hours of troubleshooting, the whole layout would shut down and show a short on the PSXs. It would re-set and come back on after about 4 min. or so. AFTER about 2 hrs. the system (track power) would shout down (show a short) and NOT come back on after the 4 min. That’s when we ceased and desisted.

It does not seem to be a thermal issue with the command station. Nothing is hot or even warm and this has not been a past issue.</

2

How long after you wired up the reverser for the wye did these problems start? Since that’s the most recent addition, it’s the most likely suspect as well.

Check not only the wires going to the track, but also the wires going to the PSX’s. Since you have a system-wide failure, it’s more likely to be early in the wiring chain.

3

Thanks Mr. B. The railroad ran for about a week just fine after the AR install but it was the lst thing I checked. It seems to be hooked up correctly and it’s definitely not caused by running a train across the gaps. Although they ARE parallel instead of staggered only one loco can turn on that arm and nothing crosses both sides at the same time. So far it’s nothing that can be determined visually…

4

Start pulling back bit by bit. Disconnect the track wires out of the DCS100. See if it comes up normally with no short. If that’s OK hook up the first PSX, disconnect the wires to the track. Gradually add stuff back until it dies - you found the location of the problem.

–Randy

5

Thanks Randy. So are you saying that IF the short is in the DCS 100 that’ll be obvious by it’s malfunctioning (improper Led messages/alarm beeps) BEFORE and signals go through the (now absent) track wires from the 100? I understand the isolating each PSX to see what happens next part.

I think my buddy may have done that as he was removing and replacing wires. He’d just driven about 250 miles when he was nice enough to swing by so I didn’t ask too many questions yet. Tomorrow though.

I’ll get back and post when and if…

Thank you.

Jim

6

When adding to an electrical system be it dc or dcc. The last added is normally the thing causing the new problem. With that said, I have seen a single strand of wire cause a short. It sounds like you have a short causing the sound you hear coming from you Logo’s. The system is protecting itself and when it can’t do so it does a full system shutdown.

I would disconnect the auto reverser to test the system. If things run normally check the wiring of the auto reverser. If the system still shorts out I would disconnect one power district at a time and recheck the system. When you take the section that is shorting out of the system, the system will run as normal. Then you can troubleshot that section.

Have you seen this page? Short Protection. While this does not stop shorts from happening it does give the short something to do other then feedback into the control unit. On a side note; The more current you draw on the power unit the brighter the bulb will glow. If you install one in each power feed the section with the short will glow brightly. While the others will not glow as bright or some times not at all.

7

Thanks Johnny Reb. I’ll go through the processes both you and Randy have described. I’ll let you guys know what we find.

Randy the part that I was confused about… did you mean that the track wires going in and out of the 100 could be shorting the 100/command station rather than the other way around? If that’s the case I think I get what you were saying now.

I appreciate the help. To be continued…

8

Capt. G,

Think about it for a second. Your answer is almost surely embedded in your question.

You have been running without issues for a long time but, suddenly, you are experiencing short circuit indicators on your PSX and it shuts down both the main and yard although they are on separate busses and power districts are in place via gaps in the tracks. The only new addition was an AR PSX board for a wye.

It’s gotta be the PSX, not your command station which was performing flawlessly until you installed the PSX. At least in my mind, the only question is: did you screw up the wiring or is the PSX faulty?

I own several Digitrax AR-1s but not any PSXs. However, I have read about problems with the PSX and compatibility issues with certain Digitrax DCC equipment. So if you are convinced that your wiring is flawless, which apparently it was until you added in the PSX, then the problem is in the PSX. However, if I were a betting man, you screwed up the wiring.

Let us know what you find out.

Rich

9

It’s highly likely that it’s the new addition - is the autoreverser connected directly to the main bus or downstream of one of the breakers? The PSX-AR does NOT work downstream of a PSX regardless of what Tony says. There’s no need for it to be protected by a breaker anyway, it has one built in.

What I meant by disconnecting at the command station is that this will test if the problem is internal to the DCS100 or elsewhere in the wiring. If the shorting keeps happenign with no output wires connected to the DCS100 then there’s an internal problem and it needs a vacation to Florida.

My bet is going to be that one of the gaps in the wye closed up so it’s not completely gapped allt eh way around. That would explain why it worked for a while then finally died.

–Randy

10

Another possibility that has not been mentioned by anyone – a shorted wheelset in a piece of rolling stock or a locomotive with an internal short circuit.

Remove ALL locomotives and rolling stock from the layout. If no short, then it’s definitely one of them. Replace them one at a time until the short returns, and that one is the defective item.

We have had an old, uninsulated wheelset show up on a piece of rolling stock. A boxcar or other piece of rolling stock with a metal bottom, metal trucks, and metal wheelsets can also create a short circuit.

11

Heading into the train room. My buddy hasn’t called yet… Thanks Randy for getting back to me and clarifying. I can see that someday I’ll have gone through enough tribulations to just know what to look for and do, but in the meanwhile you folks are truly appreciated for your time and advice. I’ll let you all know what’s found out.

Jim

12

Maybe have the solution(s). Before I got to pulling wires from the command station, I went around and pulled everything off of all tracks. We had done this yesterday but it didn’t kick the system back on.

We knew the “new” loco was shorting out the system even after running great for 2 days. Every time it was placed on a track it killed the system. What I just now discovered is that my Big Boy ALSO is shorting out the system. One of the traction tires “hit the road” on it’s own.

I can now get the entire railroad back online if I leave those locos off the tracks. SOMETIMES when I reboot the system the Big Boy cooperates, sometimes it pulses and clicks. Other times it just kills the system.

I’m not sure why, yesterday, the PSXs didn’t come back online until 4 min. or so and then…never but at this point I’m not sure if the Big Boy was on the track or it just was unhappy after the new loco shorted things out.

SO: My big question (of the moment[;)] is"

Why are ALL of the properly gapped power districts shutting down (the entire system)?

Why isn’t the “sick” loco only shutting down it’s OWN district?

I’ll continue troubleshooting with the locos as opposed to the PSX, AR and Command Station for now.

I do need to understand the gaps/power districts not isolating the problem when they always did before yesterday.

The quarter test works fine now. All power/districts come back up after the usual couple of seconds (PSXs).

I WILL try isolating the command station for practice trouble shooting for the future too, but for now I THINK I’ve found the problem?

Thanks Cacole for the suggestion to pull EVERYTHING off the layout and start fresh yet again. I was pretty certain we’d done that yesterday as we kept troubleshooting lists but we also got pretty “punch drunk” by the end.

Let me know if there’s anything else to try other than just running everything I’ve got for awhile and see if problems return or not. At l

13

Just simply start by only hooking up one of the original sections. If the breaker doesn’t trip then ONLY hook up the new section in question. If it trips that’s the problem area.

Chances are the reverser is the issue.

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Probably because one of the rails isn’t properly gapped or something is miswired - - - from the autoreverser, maybe?

If the layout is properly wired and the rails are properly gapped, only the power district involved in the short should shut down.

Rich

15

Ok thank you. I’ll move on to the AR and Command Station and PSX checks next if things don’t continue to cooperate. I’ll let you guys know, It might take a couple of days if things SEEM to be ok now.

From auto repairs, I’ve always checked the last thing done lst. (the AR) but the guy who wired it in thinks it was indeed done correctly and so do I as it worked fine (with finger flipping of the turnout points) and I could turn locos without issue for about a week. That should tell me it’s working properly (even without a tortoise installed) yes?

I’m going to take a breath of fresh air and peek at the sun while things seem to be working again.

16

The lack of a traction tire should not cause a short circuit. We have several locomotives at our HO scale club that originally had traction tires and they all run without them. The short is from something other than the traction tire.

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That’s what I thought but wanted to check. NEW diagnosis: The new locomotive IS NOT the cause of the shorts. Probably neither is the Big Boy…

When I lst turn on the system with the new loco (the Powerhouse/BLI Mikado) it was causing the entire layout to shut down (even with the gapped tracks) when it was likely just one of us shorting out as we placed the loco on the powered up track. Normally the PSXs would come back on pretty instantly.

With the current “mysterious situation” the system has to be cold started/rebooted.

I try to always turn off track power with the throttle before placing or removing locos to preserve decoders but I don’t think we both did, yesterday. We thought the loco was the CAUSE rather than a symptom of a wiring problem. So…it’s now onto the wiring connections at the AR and command station.

My buddy hasn’t been able to make it today afterall so I’ll tackle that tonight or in the a.m.

The loco’s decoder did switch back to default address 03 but that’s probably from the track power on replacing.

Frustrating, but I’m learning my troubleshooting skills with DCC and chasing the “ghosts”.

Thanks.

18

These gaps- are you using insulated rail joiners at the gaps, or gluing plastic into the gaps? If you’re just cutting the rail and not putting some kind of insulating barrier between the rail ends at the gaps, I wouldn’t consider them reliable gaps.

Without some kind of insulating barrier in the gaps, all it takes is a few degrees of temperature swing to close up the gaps electrically. Or someone running a bright boy over the rail and sliding the ends together.

You don’t want to cut corners when putting in rail gaps.

19

Sorry, I meant to say in paragraph 2 above that the track power would not come on until I removed the new loco from the tracks. Once it came on, I could replace and run that loco just fine.

20

Some years ago, in my DCC infancy, I was getting random shutdowns in power districts. I have two PS fours and two AR ones (they were PSRevs back then).

I was running an older set of A-B-B-A Stewart f-7s and I would get a short (actually an overload) and I could not find a problem with the individual locomotives.

Then I read the directions for the PS four and remembered the jumpers for the current trip setting (JP4) and the response time delay. As shipped the PS four is set to trip at 3.8 amps. I then soldered short jumper wires to pins 1-2 & 3-4 at JP-4 to raise trip current to 7.2 amps (running an 8 amp Super Chief)

Problem solved. I kept the response time to 10 milisec. These Stewarts were Kato drive, no sound but they must have been drawing enough (heavy train, old, sticky lube?) to trip at the 3.8 amp setting.

Also cold inrush of lots of lighted passenger cars and capacitors across some decoders will increase the startup current to the point of looking like a short to the PS four.

Might not be your particular problem but something to consider[:)] Good Luck… Ed