OK, I've drawn up a schematic of the layout and confirmed the (-) and (+) wires are where the drawing shows.  

I think I will do exactly what one of you suggested, i.e., cutting the buss wire and temporarily connecting the DCC command station to that part of the wiring to see if that is where the problem lies.  I can wire-nut it back together once done.  

Thankfully I didn't wire all the layout, with about a third left to be done.  So I will break up what is wired into halves and see what is to be seen.

I will run a vacuum over the track to be sure there are no lengths of solder or other metal stuff hidden away.  I'll report back what I find.  

Thanks to all who responded.  I was pretty done-in yesterday and I could not come up with a plan of attack.  What you've all suggested has been helpful.

I can post an electronic copy of the pdf but I don't know how.  Some guidance would be appreciated.

Scott Groff

One thing you could do is start by cutting the rails to isolate the layout into 2 or 4 sections, then power those sections separately.  This will further narrow down where the short is with out cutting feeders... then at least you have a fighting chance.

As Seanm suggested cut your rails at a point that is electrically in half, then power each half separately. The half that doesn't have a short leave alone. The other half that has a short cut in half. Keep repeating this process until you isolate the problem area. I have used this procedure to find problems in burglar alarms and it works great. After you find the short you may want to keep the sections in "blocks" with toggle switches or with separate block powering to allow for easier future troubleshooting.

What I've done is to prop my Zephyr up so I can see the display to determine when a short disappears.  I started on the end of the layout where the crossing was located.  Take notice of the tense.  

When I cut that section off, I got shorts where it wasn't possible; along the same section of track.  Black and red wires where in the same relative locations connected to the appropriate buss wires.  

I then isolated the Peco crossing and found there to be a defect.  There was continuity between all the south rails and two of the north rails.  So I've eliminated that device and am now cutting off another section of the layout to track down re shorts.

Scott

Dear Scott,

Without the track schematic, we're "flying blind" alongside you...

if you've got issues attaching or posting the PDF schematic, email it to

loggingloco1 at yahoo dot com dot au
(convert the bold text into appropriate characters)

and we'll get it post up on the list for you... :-)

Happy Modelling,
Aim to Improve,
Prof Klyzlr

I found two problems with the layout, after disconnecting all the soldered feeders one by one.  The first problem was a defective Peco crossing that had a dead short in it.  That has since been removed and this schematic reflects that.  

Of the twenty or so feeder wire sets I connected the day I found there was a short, the very last one I did was the problem set. 

The second problem was a modified Peco switch where the two PC ties had not been completely isolated.  The cut groove was there, just not deep enough.  

I am reusing the HO Peco switches for this new On30 layout.  I removed every other tie in the switches, and in a bunch of Atlas flex track.  While I was cutting switch ties, I modified the Pecos by removing the original throw bar and head block ties, replacing them with PC ties.  I also narrowed the switch points to NMRA standards, as well as the guard rail clearances.  Lastly, I made all the Insulfrog and Electrofrog switches into insulated frogs that can be power switches using a Hex Frog Juicer.  Hopefully, these mods will eliminate the frog point shorts.  I put this part in only because you might be wondering where did PC ties enter into the picture with Peco switches.

So far, no more shorts although the wiring is not complete yet. I've since followed your suggestion and broken up the layout into three segments, electrically isolated and controlled by a DPDT on-off switch.

Scott Groff

Dear Scott,

I didn't see any schematic with your post, so the "...and this schematic reflects that" comment has me a little puzzled. However, it's great to hear that you got to the bottom of the issues!!! :-) 

That there was more-than-one issue causing a "compound fault" only goes to support some of the poster's suggestions that "check as you go" (and in the case of the crossing and turnouts, even before any wire is introduced) really is the way to "doing it one time, and being confident you don't have to look back..."  :-)

The shorted-crossing sounds like an odd one,
but is always a possibility with re-used track. (errant solder blob from previous wiring, etc).

The not-fully-insulated PCB ties are a "oldie-but-a-goodie" gotcha,
(why can I hear Maxwell Smart in the background?)

and always worth a laugh _after_ they've been found, repaired, and resolved...
(Inevitably the laugh being the un-verbalised feeling of
"...I'm _not_ going crazy, there _was_ a logical explanation for the short condition...")

"For now", everything is operating and the fun can resume. The adding of Isolation Points in the wiring will definitely repay in future of any issues rear their ugly head,

although Murphy is likely to figure that now there's a way of fault conditions more easily,
it's time to leave town... :-)
(one can only hope...)

Happy Modelling,
Aim to Improve,
Prof Klyzlr

  That's good to hear. I can sympathize, I spent an hour soldering feeders under my shelf layout this afternoon and now my neck hurts :>)  Seemed a lot easier last time I did it but so does everything else....DaveBranum

Someone on this forum offered to post the schematic if I'd email it to him, and I did that but haven't seen it yet.  I couldn't see any way to attach the scanned drawing when I was first asked to include it.

Scott  

  When you go to the post new comment screen look along the tool bar with all the little symbols and find the one that says "image" when you hover over it.  If you click it you get  screen with a tab marked "upload" as one of the choices. Click the upload and then browse your files till you find the drawing then click send it to server. It will load then show you a preview of what it looks like, you might have to type in a smaller size in the width or height box, IIRC neither can be over about 700....DaveBranum