Engine

Is there a DCC equipped engine on the tracks?

Track continuity

A reading on your multimeter when touching the probes to each rail means there's a short circuit (the circuit is closed).  If there are no locos or cars on the section of track, and the transformer is disconnected, getting a reading on the multimeter is no good (also assuming the power bus isn't connected back to a DCC circuit breaker).  When there is no reading on the multimeter, you have an open circuit (which is good).  Is this district managed from a circuit breaker or booster?  You mentioned the locomotive runs fine when the district is connected to a DC transformer.  Is the whole layout going to be DC, or DCC?  If you're planning to run DCC, have you tried connecting your command station to the section and running a DCC-equipped locomotive?

One more thing, if you are running DCC and you have your layout broken out into power districts using circuit breakers, do not test the districts with a DC power pack connected to the circuit breaker.  You'll fry it.  I always test by disconnecting the outbound wires from my circuit breaker, and then connecting to the DC power pack.

Jonathan

@Dave1905, I'm going to have

@Dave1905,

I'm going to have to ck on that. I think I may have a little switcher engine on there that I believe might have a decoder.

I have also run a couple of larger diesels locos that I know do NOT have decoders. And i have run one steam engine that has no decoders.

BTW, I have NOT hooked up any DCC yet

No DCC yet

I have NOT connected up any DCC yet!
 

i do plan on having the entire layout run under DCC, but I am trying to be very cautious and only test under straight DC to begin with.

Back feed

BTW I did think that perhaps because I had the DC transformer hooked to the one end of the bus wire(s) that it might be providing that electrical link between the two tracks (even while it was NOT turned on). So I disconnected one wire, and still experienced the apparent continuity between the 2 rails?....no transformer

No Locos

Make sure ALL of the locomotives are off the track.  A DC locomotive will definitely read a very low resistance that may look like zero on your meter.

No loco, no cars, no power supply, no tools, you have

A short circuit.  Are you wiring?  Are you using a buzzer or other short indicating device as you go?

Is your whole layout one big electrical zone, or is it broken into sections.  IS only one section shorted?

Have you left a metal tool on the track in some corner?

There's lots of ways to inadvertently short a bus.  Let us know which you have discovered.

Blair

Test with DCC

It sounds like you've got a short, but test with DCC. A true dead short will stop DC from working as well, but some issues like momentary shorts will sometimes be tolerated by DC power packs, but not by a PSX breaker using DCC.

  "For testing purposes I

Hi Brian, Can you clarify. Did you run DC engines on this track with no problem ,then later found that the ohm test shows continuity between the rails?  Are engines or any other cars on the track during the ohm test? Did you add new feeders recently that might have one cross wired, or maybe left a metal tool or track gauge on the rails? ......DaveB

coil

Hi,

it is good to know, that coil is just a wire. It mean, for DC voltmeter it mean short.

You have coils in DC motors, you have coil in transformer, etc.

Once you want to measure something by DC multimeter, you have to disconnect all electronic parts (including locos).

Capacitance or inductance

Hi,

congratulations on running your first train!

Long, long ago I had a case when plugging an extension cord into a household outlet resulted in the circuit breaker "giving up". The solution to that problem was to replace the extension cord with a shorter one that was not on a spool. Same load, no breaker. It turned out there was just enough capacitance and inductance in that spool to overload the breaker.

Applying that info to your question - please make sure to disconnect any "extras" before testing for continuity. Those "extras" include your DC power pack, locos and wagons on the track, but also the spool of wire that may be attached to the end of your bus wire... Similarly, make sure there is no other track connected to the section that you're measuring (you're checking a single power district, right?).

Finally, even without any "extras," the power bus and track do have a bit of capacitance. Please allow for your multimeter to take a second before you get a stable reading. I've had a multimeter's short detection beep shortly when touching a large enough circuit. It should stabilize in less than a second, unless you have large capacitors in there somewhere. A loco with "current-keeper" would qualify as a "large capacitor" (your multimeter will not like that).

What about your turnouts - does switching them make a difference?

With my layout being a small DC layout, I'm currently wiring two "collector" boards into the layout. Everything which requires power is being plugged into those boards - so that I can disconnect track/turnouts/... easily to find an error as well as exchange connectors if I have mixed up some wires... With a DCC layout, it may be useful to have screw terminals in strategic locations so that you can isolate a section in order to find an error. Obviously you'll need to have isolation gaps in the rail, too.

Have fun!

PS: To anyone who said that DCC is simpler than DC - in some ways it is simpler, but in other ways it is not. It's just - you can do more with DCC than with DC if you're willing to try

PPS: sorry, the "PS" is not meant to cause any irritation.

Test Set-up This Morning

So here is the test set-up I used this morning. I used two different multimeters trying to see if that made any difference?

I also selected 4 different locos for the test,...all of which I am pretty sure are DC only. The one questionable one might be the Atlas switcher.

I specifically left the DC power pack unpluged and NOT attached to the bus wire at either end of this portion of tracks.

This time I measured infinity ohms across the two rails of any track WHEN any of the locos were NOT on the track. When any of the locos were on any of the tracks I got the zero ohms measurement. I surmise that the wiring in the locos themselves were giving me this 'shorting problem' that I thought I was experiencing when I first posted this thread.
 

Furthermore I hope I can believe as a result of this test that all of my feeder wires are correctly wired for this portion of the layout,...since I did not experience any zero ohm measurements??

So either

you still had a DC or DCC loco on the tracks and were measuring the resistance of the loco motor(low ohms), or you had your multimeter in Volts mode, with no power pack attached, with or without a loco, and reading 0 Volts.  That's very common, and one of the drawbacks of a multimeter.  Jumping back and forth between measuring ohms and measuring volts(as one often has to in the electronics world), sooner or later you try to measure one physical property, while set for the other.  It happens.

Glad you're not digging further, looking for cross-wired feeders.

Blair

Back Side of the Circuit

I think one of my very early problems with understanding electrical circuits is I just failed to recognize the 'backside' of the circuit.    hope I expressed that correctly?

Can't tell,

no idea what the backside of an electrical circuit is.  So whatever.  You're past it, so move on.

Blair

Some extra testing

Hi,

congrats for solving your problem

Some extra testing is always good, so you should consider the "scare" to be good motivation Have you tried to flip all the switches with the multimeter still attached?

Have fun!

PS: Blair, yes, been there done that... I recently exchanged two old multimeters for one new one (couldn't find a replacement 15V AA special battery) and I'm delighted to have the new multimeter actually display the unit being measured in the display. Just one extra reminder It doesn't hurt that the new one has auto-ranging, can measure capacitance, ...

Have you tried to flip all

I have not tried that experiment,...perhaps I should?

I do know I tried running one of those DC engines over ALL of the tracks, so I assumed that confirmed it correct,...no shorts??

Yesterday I was getting to a

Yesterday I was getting to a point on the lower level of my layout that I was going to run a train around the entire perimeter,...hallelujah !!

Oops, I discovered I have another short in that freight yard section I was so proudly proclaiming fixed, ..or at least it must be a short, as I took all cars and engines off the tracks, and still measured zero resistance across the 2 rails,..everywhere in that section.

I looked again at the 3 new feeder connections I had made to the buss wire on that side, and saw nothing wrong? I will attack the problem again today. I just LOVE electrical problems
 

i was so looking to run a train around the entire perimeter.

Finding shorts

  I find the easiest way to avoid them is to check for shorts any time I add new track or wiring. If I work on the layout for an hour or two I always turn on the DCC and run a train across the new work before quitting for the day. If I worked on the layout all day I'd probably check it every couple of hours. This method make the amount of wiring or track possibly installed wrong to be much less. The only time I've found a problem on my present layout is when two spikes at the edge of a turnout frog gap were touching and bridging the gap. Since I'd only added two turnouts and some feeders that day it was possible to find it without too much effort....DaveB 

Found my Problem

I decided to attack the short problem in the reverse order that I have installed new connections that day. I got lucky, the very last thing I had hooked to the buss wire for that side of the layout was some sections of track and a turnout that feeds steam engines to the turntable. Here is that turnout and its short feeder tracks,..
 

As soon as I disconnected the feeder wires on either side of this Peco electrafrog turnout, my shorting problem for the whole district disappeared. I still do not understand exactly why this turnout shorted out this side of my layout, but I didn't want to dwell on the reason,...just cut another insulation slot in both diverging rails rather than just those connected to the frog.

The GREAT NEWS is that I hooked up those 2 power districts to separate DC power packs, and was able to run some trains around the entire layout, including across my entrance-way bridges. THAT WAS A FIRST for my layout !! Running trains around the perimeter !!

I next moved onto soldering the track joiners and feeder wires for the peninsula trackage. Tomorrow I should be able to run trains in the peninsula area,...GREAT feeling as its been a long time coming  !!

Check after adding each feeder to your bus

Past experience with electronics has taught me that going through and wiring up a whole bunch of connections before checking any of them is a recipe for aggravation.  That's why so many people recommend using a buzzer to tell you if you've created a short, but it's really only a few seconds longer to use a multimeter. Keep one side clipped to the opposite rail from the one you are working on, and then check the meter to see if the resistance drops; if it does, you've crossed the wires.

Good luck.

Janet N.

No Crossed Wires

That is one of the things I am not understanding here. I didn't cross any wires, but the electrofrog Peco managed to create a short when thrown in one direction.

JanetN,   You likely have a good idea there to hook up a meter and check it as each new feeder is installed.

I vote for the buzzer,

because it tells you you've created a problem instantly, without any action, even if I'm on my back on my creeper under the lower staging yard; no need to find the multimeter, touch anything, or look away from my work.  Just touch the feeder to the buss you're about to connect to, and in the process of fastening it you'll KNOW it's a mistake.  It's really simple.  When wiring any buss, I disconnect the two buss wires from the system (usually, the output of the PM42/PSX/PSX-AR, but sometimes just a sub-element of that), attach the buzzer, and go to it.  I know I'm wiring the right feeders, because they're colour coded, and I know I'm wiring them right because the buzzer is silent.  Every now and then, I deliberately cross the feeders to check that the buzzer's alligator clips haven't disconnected from the buss wires.  It's that easy, for the vast majority of my buss wiring tasks.

Blair

Buzzing Meter

I suppose you are speaking of a buzzing multimeter? Where do I find a reasonable priced one??

I think I just saw one being used on a 2 speaker installation video posted on this forum. The fellow was using it to check his wiring between loco and tender, and wiring of the tender.