It could be some of the

It could be some of the bonding solution bridged a gap some where and is causing the short. I would leave the PM42 disconnected as well as the DB150. With the power off take an OHM meter and check all the gaps to see if one is bad. Check both sides of rail A and B. Check the throw bar on the turn outs.I would even check between rail A and B.  Hope this helps.  Joe

Yikes! Sounds like you have a

Yikes! Sounds like you have a nasty little problem here.

When you said you measured a short, how were you doing that? Ohmmeter? A short detector with a beeper?

Had you taken the locos and cars off the layout first?

Have you tried running the DB150 with just the PM42 but no layout connections?

Did the layout run successfully after the ballast was glued in place?

If not (the short was found during the first post-ballast ops attempt), what did you use to glue the ballast?

Have you stuck the probes for an ohm meter into the ballast an inch or two apart from each other (not touching each other or the rails) to see if the ballast itself became conductive?

When the short occurred was the train on a turnout or on standard (straight or curved) track?

Good luck with thi

To answer your questions, I

To answer your questions, I used a meter with an audible beep to detect the short. I've taken all the locos and cars off the layout. And yes, it ran successfully after the ballast was glued in place. I haven't tried sticking the meter probes into the ballast...I'll give that a shot.  But because it ran after the ballast was glued, I can't imagine that this is the problem. The short occurred when the train was on a curved mainline section, about 5 feet past where the new ballast was glued in place.  Really don't know what to do next, short of the tedious task of cutting the feeder wires. Any other ideas would be most appreciated.  Thanks for the help!

Perry

Do you spike your hand-laid track?

If so, can you account for all your "escaped" spikes? Do you use circuit board ties anywhere and are all the gaps still clean?

Audible shorts

You *may* be able to hear the short circuit as a "chirp" happening about once a second if you listen carefully.

Get the house quiet and put your ear down near (not on) the track.

Somebody didn't wedge a screw into a turnout someplace where it bridges a gap did they?

Charlie

Fallen debris? Crossed wire? Cats? Dogs? Metal wheels?

I would look for fallen metal debris that may be bridging a gap or a rail.  I know this is very frustrating!  (Been There done that! That's why i now have districts!!!!!!!!) also look UNDER the layout in the area you last worked on to start and work from there to look for a crossed wire or something out of place.  (Cats and dogs do crazy things!) Even if you dont have pets, look under the layout!  Also metal wheels can cause a short when a car stops on a frog. Methodically go through everything.  Believe me it WILL be something stupid! 

P.S.   Check for a bad switch or auto reverser in your reversing sections.  Also a closed gap will do this. 

Mike, most of the track was

Mike, most of the track was laid with a Kadee spiker, but there are some sections with regular spikes. I don't use circuit board ties anywhere, and I have checked all the gaps, and they are totally clean. I even vacuumed the entire layout to possibly pick up any un-seen metal shavings (or spikes), but that didn't help. BUT... I just tonight started cutting the power buss wires to try to isolate the short, and I got lucky. The second section I cut through eliminated the short. The buss wires connect to a branch line section of the layout, and with that isolated, the rest of the layout works fine (the double track mainline, yard, turntable, all sidings and reversing sections). The branch line is still a section with about 80 feet of track, but at least I don't have to go through the entire layout. BIG relief.

Charlie, the audible short idea is interesting. However, when I connect DCC power, the DB150 constantly beeps with the "short alert," so it may be hard to hear above that. But I'll give that a try. Question: If I keep the DB150 powered on with the short alert signal going continually, is there any possibility I will damage the unit? Unless I am missing something, I don't see any other way to do this.

To answer your last question, there is no screw or anything bridging any gap. I checked every inch of rail, and there is nothing visibly wrong...so it must be something under the layout. But that makes no sense, as there was nothing that would have cause anything to move. There are some exposed, un-insulated feeder wires, but they are far enough apart from each other that there is no way they could move and touch each other. But I guess I'll find out once I start looking. Part of the branch line section where the short is located is where I recently added the ballast, so I'm wondering if it's related to that. But as I said in a pervious post, everything was working for about a half hour the day after I applied the bonding agent to the ballast, so not sure how that could be related.

Thanks for all your help, guys.

Perry

What happens if you disconnect the feeders to the

newly ballasted section of the branchline?  You could perhaps try jumpers as a temporary replacement if necessary as a test.  Are all the uninsulated feeders in the ballasted section or are there more elsewhere?

Good job on isolating the

Good job on isolating the short to the branchline!

A few more questions:

Did the short come and go depending on the position of the switch connecting the branch line to the main?

What about the position of any switches on the branch?

Was the branch line where your train was when the DB150 first started complaining about trackwork shorts?

Charlie

short isolation with a meter

Use the ohmmeter as a relative measurement rather than an absolute device.

If you have a meter that will show an indication of less than around 10 milliohms, moving the probes over the affected area in a systematic  way will show the resistance changing as the probes move.  At some point the resistance will stop going down and start to increase.  The short is near the point where the resistance is lowest.  It's a lot easier than cutting feeders.

As an aside, the resistance of my 40 foot code 83 railroad measures out to about 3 ohms with no feeders attached and one end shorted to give you an idea of the resistances involved.  Probe, connrector and switch contact resistance is in the 10 milliohm range per contact.

Terry

Mike, there are uninsulated

Mike, there are uninsulated feeders all over the layout (I used the thin gauge, uninsulated, pre-tinned wire from radio shack, which of course made soldering to the rails much easier). I was careful to stagger the A/B rail feeders along he buss wires so they are not near each other, which is why I cannot imagine that this is the issue under the branch.

Charlie, the short is unrelated to the position of any turnout, including the one connecting the branch to the main. The train was not on the branch line when the short appeared; however it was about 5 feet beyond another section on the mainline that I also had ballasted a day earlier.

Terry, thanks for the tip about using the ohm meter. I'll give that a try.

Perry

Is is possible that some of

Is is possible that some of the gaps in a turnout have closed back up on the frog causing the short?

Makes me wonder if a nail or

Makes me wonder if a nail or something got mixed in with the ballast or was under the rails. As the glue dried, it floated up and contacted the botton of the rails.

Scenery involvement?

What do you use as your scenery base, Perry?

A few years ago, a buddy of mine who handlays all of his track with a Kadee spiker added a couple of inches to some of his sidings in a town. In the process he extended the track onto an area that was formerly just hardshell scenery supported by aluminum screen.

A couple of weeks after doing this, things expanded and contracted a bit, and the spikes made contact with the screen that was under the new bits of track, shorting the wiring around that part of his layout.

Found It!!!

Well, it did turn out to be something stupid, as Nelson predicted in an earlier post…but was in a hard to reach and hard to see area under the layout. Recently I worked on a new area of scenery that consists of a rock wall constructed using suspended ceiling tiles (if any of you are not familiar with this method, the tiles are scored and broken by hand…and when stacked up and painted make a wonderful representation of stratified rock). This rock wall extended upward to meet the underside of the roadbed supporting a section of the branch line (the branch on which I had isolated the short).

Apparently when I was stacking the tiles and pushing them into place, I unknowingly caused one of the naked feeder wires to break from the solder joint at the buss wire; however I still had continuity because of the rail joiner.  This particular feeder was longer than most (about 10 inches or so), but normally had no way of contacting the next opposite rail’s feeder wire along the route.  But when broken free, it was now long enough to reach.  And of course it was touching the next “staggered” feeder in the route, causing the short.

What is so perplexing about this is that I built this scenery section about two weeks ago, and never had a problem running locos until a few days ago. Did the wire move on its own?  I can barely reach it when under the layout, so nothing can even get to it.  Maybe it had to do with a temperature variation that caused something to move (or maybe the ballasting I did the day before somehow caused a delayed movement). In any case, problem solved…and again I got lucky because this happened to be at one end of the branch, which is where I started looking.

Thanks again for all your input! It never ceases to amaze me how helpful everyone is who is a part of this hobby!  Next project: Divide my layout into power districts!!!

Perry

Did your feeder perhaps have a cold solder joint?

I'm wondering if your scenery work applied pressure to it until it finally (belatedly) broke free, allowing the feeder to flex in the direction of its neighbor and make contact.  That would make the time of the short's onset somewhat random; that it did not create an immediate short but later while running a train elsewhere on the layout made for a great red herring! 

What type of splice do you use when attaching feeders to the buss?  I'm curious how the two could have been pulled completely apart.  Do you use tap splices?

Personally I think I'd take another look at doorbell wire, at least it's insulated.  How many feeder ends could you have tinned in the time it's taken to find and fix this? 

Mike, good point regarding

Mike, good point regarding the time trade-off of tinning vs. trouble shooting.  In hind site I probably should have just used insulated wire. As far as how I attached the feeders to the buss...I used a wire stripper to separate a small section if the 14 gauge solid buss wire insulation, wrap the thin feeder wires around the bare core several times, and then solder it.  I doesn't look like a cold solder joint here; just a broken wire.  My guess is that I may have weakened it at the joint when wrapping it just enough so that whatever happened this week caused it to fail...but this is only a guess.

Your idea of the scenery work applying pressure to the wire causing it to eventually break makes more sense than my guess that something moved due to temperature. Funny how sometime I can do everything possible to be so careful, yet end up doing something stupid like this! But  I'm sure I'm not alone in that

By the way, how did you attach the image to your post?  That's something that would be nice to know for future discussions.

Thanks again, Mike....

Perry

If you count that as stupid...

...then I'm personally guilty of things that surpass even the moronic! 

As for posting the image, the steps I used from WinXP/Firefox were:

1) Google "tap splice" to find a decent image;

2) Right click on image, then "Save as" to my desktop (so I could find it easily);

3) From the Post input box, click on the "Image" button (second to left from Flash icon);

4) From the "Image Properties" popup select the Upload tab;

5) Under "Send it to the server" label, click on the "Browse" button and go to the desktop and select the copied image file;

6) Click it on the "Send it to the Server" button;

7) Click on OK--then play with your post until you figure out how to position the image just where you want it.

Voilà!

Modular Wiring

This is why I like modular wiring even on a fixed layout. With connectors or terminal blocks scattered around the layout, isolating problems is an un-snap. For Power and DCC buses I use Anderson Powerpole connectors which are the recommended replacements for the old Cinch connectors on modules. They are low resistance, high reliability and high current only costing about $2 a set in low volumes. OH! - They come in 10 colors for color coding your wiring. If you have not already soldered the bus wires back together, or even if you have, you might want to consider adding some disconnects to prevent future migraines.

Great suggestion on the

Great suggestion on the modular wiring, Ken...Thanks!

Okay, just to try the image upload thing...here is the section where the short occurred after I built the rock face. Obviously this is just the scenic base, and hasn't been detailed yet at all. The short was about 6 inches before the turnout entrance (you can barely see the turnout just before the tunnel entrance from this view).
 

Perry, One part of your

Perry,

One part of your problem I do not think is resolved yet.  You commented on how difficult the problem was to isolate. Part of the reason is that your DB150 is indicating the short and not your PM42 channels.  Properly set up, the PM42 should trip BEFORE the DB150.  Had this been occurring, you would have at least known which quarter of the layout to look at. 

Correcting this problem is not as easy as it may seem.  The obvious first step is to check and see what the setting for OPSW 18 in the DB150 is set for.  You want it "C". for 1/2 second response.  This allows time for the PM42 to detect the short and remove power from the shorted district.  Change the setting and run the "quarter test" by shorting each PM42 district.  This sometimes is all that is needed.  If the DB150 still beeps and shuts down, you have other issues.

The PM42 has both response time settings and current capacity settings.  You want to use the fastest, lowest current settings that permit you to operate.  Those settings depend upon your locos, whether you have sound, lighted cars, etc.  I have found that the design of the PM42 is not the best for controlling modern sound equipped fleets of loco's.  This is due to the high inrush current of starting up a district with several sound locos on it.  On several of my club members layouts, we could not get the PM42 settings between the fast response time needed to keep from tripping the DB150 and the current capacity needed to start the sound locos.  The PM42's had to be replaced with PSX boards.  PSX boards have several soft start features that will help a weak booster start sound loads.

Lastly, the distance from the PM42 to the power district being controlled can be a factor.  Long runs of even 14 ga wire can cause issues of voltage drop.  The PM42 is looking at voltage drop as a short indicator and may be confused by the drop in your wiring.  If the runs are very long, try this easy test before changing to heavier gauge wire:  Parallel another 14 ga wire temporarily with each of the first pair between the PM42 and the start of the first feeders.  Do the quarter test and see if the PM42 cuts out correctly.  If so, replace the original runs with # 12 or # 10.  You do not have to replace the bus in the district, just the long run between the PM42 and the first feeder.

Hope this helps.

Morris

Try another train

You mention the short happening when the train entered a curve near the new ballast.  Try another train.  Sometimes an engine or car might have a clearance problem when trucks swivel that shorts metal wheels against a metal floor, frame, etc.   The new ballast might be just coincidental. 

Another Weird Short

This reminds me of a problem our modular group had last year.  We use a short section of PC board at the track ends to provide alignment when the modules are connected.  We gap the PC board to prevent shorts.  On one particular module we had used it for a number of shows, but just before the NTS in Grand Rapids last year, we did some touch up of ballast on the end where the PC board was. 

After we set up at the show we found a short in one line.  We were able to isolate it to this module by unplugging modules (one advantage of modules).  We started trying to find the problem on the module, not thinking about the last minute ballast, as the module had bee completed months before.  After an hour or more, of cutting feeds, gapping rails, etc we had isolated the problem to a six inch piece of track between the end of the module and a switch.  Out of desperation one of out members grabbed a metal pick and ran it through the gap in the PC board.  Problem solved.  We are not sure whether it was a sliver of PC board material or possibly a conductive particle in the ballast, but something was in there causing the short!

Bottom line, I understand your pain!

Ghosts

That wire didn't move on it's own...the ghost did it.

I live in a 300 year old house and any time we have one of those strange experiences we always suspect the ghost did it.

A model RR is even more susceptible to ghostly happenings.

Dave Mason

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