I am building my own turnouts, gapping and wiring according to what I found on Allan Gartners site, Wiring For Dcc. This worked fine on my other layout. As I build the turnouts, I test for shorts and then run a loco. This morning i installed a turnout, tested and all was fine. Installed another turnout and had a short. Removed the wires and still had a short. Removed the turnout and still had a short. Removed the other turnout, still shorted. Brushed the track to make sure there was nothing across the rails. Still shorted. Tried a different loco. No difference.
So, I hooked up my dc power supply. The short was gone. For about a minute. With dc hooked up, the loco will try to run, then the overload light will come on very dim and slowly get brighter. I am at a total loss as to where the short could be or what it could be. Here is a picture of my yard, the green turnouts have not been installed yet, the red is where the short happened. No other track on the layout that is wired in.
Anybody have any ideas :?:
I got my first train when I was three,
put a hundred thousand miles on my knees.
Unfortunately, when you have eliminated all but the obvious, you have your cause.
Since the layout did not short before the work, and still shorts after the new work is removed, something has to have changed. Back when Kadee coupler height gauges were made of metal, I accidentally left one at the end of a spur where I had been testing cars. It took me 3 hours to find that short circuit. Chances are you either have uninsulated wires of opposite polarity touching somewhere, or there is something bridging the rails somewhere.
A short circuit is a short circuit in DC, AC, and DCC. The short circuit doesn't care about your power source. Switching power sources merely proved that the DCC system is identifying short circuits correctly.
If you use stranded wire (you didn't say which you use), it could be a very short piece of a single strand bridging 2 rails of a turnout. At adjacent screw terminals, a strand of a wire can go astray and touch the other terminal, even though all but the one strand are correctly connected. Of course, solid wire has its flaws, too. It can be easily nicked and eventually broken, causing a difficult to find open circuit down the road. But I digress. Another possibility are bus wires accidentally touching where you have joined feeder wires. You didn't say how you were attaching feeders to power bus wires.
Recommended trouble-shooting sequence:
1) Remove all cars and engines from the layout. A derailed car with metal wheels somewhere on the layout could be the cause.
2) Vacuum all the track. Sometimes brushing moves that invisible single strand, but doesn't get rid of it. Then check the track carefully with a bright work light.
3) A multimeter is advisable for this step. Set it to ohms and calibrate by touching the leads and making sure you read 0 ohms. Remove all power supplies by disconnecting their hookup wires. Measure resistance across the track. If it is still zero, then start removing feeders one at a time until your resistance measurement is infinite. The last feeder removed is the one that caused the problem.
4) If you are down to one pair of feeders left, and the track still has zero resistance, then it could be the feeders or uninsulated parts of the bus wires are touching somewhere. Remove the last set of feeders and now measure resistance between your bus wires. If you still have zero resistance, then the bus wires are touching somewhere.
In cases like this, there is something to be said for having the layout and power bus broken into isolated sections. Then the short can be isolated to a particular section, and finding it won't take as long.
Fred's post was excellent. One other thing to check - are your real gaps filled with something, or are they just gaps? And I assume you are using pc ties for the turnouts? all it takes some microscopic bit of conductive material in that gap and you have a short. I built a turnout, had a short, and it turned out that I hadn't sliced through the copper cladding quite all the way. I needed magnification to see it. If your rail gaps have nothing to hold them open, perhaps one rail got bumped and a gap was closed? I always put thin strips of styrene in my gaps.
-- Kevin
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Fred, thanks for the reply. I was hoping for an easier way, but I quess not.
Nachoman, I forgot to mention there is no track sections laid yet, just turnouts. So there are no gaps. And i know what you mean about the pc ties. It can be a bear trying to find the one that isn't gaped all the way.
Loren
I got my first train when I was three,
put a hundred thousand miles on my knees.
nomad Wrote:Fred, thanks for the reply. I was hoping for an easier way, but I quess not.
Nachoman, I forgot to mention there is no track sections laid yet, just turnouts. So there are no gaps. And i know what you mean about the pc ties. It can be a bear trying to find the one that isn't gaped all the way.
Loren
I assume then you have isolated the frogs?
-- Kevin
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Well, I found it. For some reason, the third turnout I tested had a short in the frog. I could find no wire, pc tie or anything else causing the short, but when I replaced the turnout, the short went away. There must have been a piece of wire under the turnout that decided to short out just then, even if I didn't see any when I pulled the turnout.
Thanks for the help everyone.
Loren
I got my first train when I was three,
put a hundred thousand miles on my knees.
The damn short is back! This one showed up the day after I ran a train testing track and having fun. I did nothing but come in the next morning and turned the power on. I have spent the last two days trying to find it. No luck. I now have every feeder removed from the rails and am rewiring the yard to begin with. So far no shorts. I think I need a few of these.
I got my first train when I was three,
put a hundred thousand miles on my knees.
After rewiring the layout I found the new short. When I laid one of the crossovers, I had one pc tie to long. When the weather warmed up the tie must have expanded enough to contact the rail on the other turnout. When I clipped the tie the short disappeared, so that must have been it.I must have sat and looked at that crossover for an hour before I saw the tie touching the rail.
Loren
I got my first train when I was three,
put a hundred thousand miles on my knees.
That's the way it always works! You go over it, and over it, and sleep on it, and come back, and finally it dawns on you. Shorts can be a bear! glad you got it solved!
-- Kevin
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I did nothing but come in the next morning and turned the power on. I have spent the last two days trying to find it. No luck. I now have every feeder removed from the rails and am rewiring the yard to begin with. So far no shorts. I think I need a few of these. 