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Short between the rails?

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  • Member since
    February 2001
  • From: Loveland, CO
  • 77 posts
Short between the rails?
Posted by cgrubb80 on Tuesday, August 10, 2010 10:05 PM

I have two main lines that are connected using two Peco electrode frog swtiches.  I have both rails isolated using insulated rail joiners.  If I try to run an engine from one main the other I short out the DCC unit.  I have previously cut the inter two rails of the switch so they would have cause a short.  I nearly burnt up the decoder in DC mode.  I melted the red wire and had to rerun it.  Thanks in advance.

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  • From: City of Québec,Canada
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Posted by Jacktal on Tuesday, August 10, 2010 10:59 PM

We've had a similar problem at the club's layout and we found out that a PL13 was faulty.I suggest you try disconnecting the switches and let the power routing function of the turnouts drive your locos through.If no short occurs,you likely have a defective PL13.If the problem occured upon installation of these switches,then you may have an error in your wiring.

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Posted by maxman on Tuesday, August 10, 2010 11:54 PM

cgrubb80
I have two main lines that are connected using two Peco electrode frog swtiches. 

Is this the only location where the two main lines are joined?  Do you have a voltmeter?

If you have a voltmeter set it to read AC volts.  Then read the voltage across each gap between the turnouts that form the crossover.  You should see no voltage reading across the gap with the turnouts set to the crossing over position because those rails should be the same phase if you have both main lines wired correctly.  If you read a voltage across the gap, then you have a phase difference which will cause the short.  Then you will need to swap one of the sets of power leads.  Note that this is a simplified answer since I don't know what the rest of the trackplan looks like.

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Posted by hobo9941 on Wednesday, August 11, 2010 12:55 AM

I once had a short problem that drove me nuts. I finally found a track spike between the rails in a turnout. No idea how it go there.

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Posted by MisterBeasley on Wednesday, August 11, 2010 6:33 AM

I'm guessing on this.  I think you have two basically independent loops, each of which operate just fine by themselves.  At one point, you have a crossover between them, and when you bridge the gap you get a short.

This indicates to me that the two loops are wired with opposite polarity, to use the DC term, or more properly phase in DCC.  Recommended practice is to color-code your track bus and feeder wires.  I have a continuous-running layout, so I wire all the outside rails of the loop with red wires, and all the inside rails with black wires.

My guess is that you have one loop wired the other way, so that when you cross between them there is a short.  If you have separate track bus lines for each loop, try reversing the wires where one of the track buses connects to the base station.  This will flip the phase on one of the loops and should fix the short if this is the problem.

It takes an iron man to play with a toy iron horse. 

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  • From: Orig: Tyler Texas. Lived in seven countries, now live in Sundown, Louisiana
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Posted by jeffrey-wimberly on Wednesday, August 11, 2010 2:09 PM

 I'm betting you have a wiring problem. Draw a diagram of your track plan with two lines for each track. Now go over one line (right rail) on the diagram with a colored pen. I use red and blue. Red for right and blue for left. If at any point the red line connects with the blue line that's your short. you would have to reverse the wires to one loop to correct the problem.

Running Bear, Sundown, Louisiana
          Joined June, 2004

Dr. Frankendiesel aka Scott Running Bear
Space Mouse for president!
15 year veteran fire fighter
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Running Bear Enterprises
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beatus homo qui invenit sapientiam


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Posted by Hamltnblue on Wednesday, August 11, 2010 3:15 PM

I agree it sounds like the 2 isolated sectoins are reversed polarity from each other.  When the loco bridges the insulated section it shorts out.

Springfield PA

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Posted by mfm37 on Wednesday, August 11, 2010 7:10 PM

 Sounds like the problem has already been described. You need to make sure that the polarity (phase) is the same on both loops. You also need to check and be sure the wiring is adequate. The breaker on DCC equipment should trip immediately when a short circuit occurs. This is what  keeps the red wire from being destroyed.

Martin Myers

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Posted by cgrubb80 on Wednesday, August 11, 2010 9:27 PM

MisterBeasley

I'm guessing on this.  I think you have two basically independent loops, each of which operate just fine by themselves.  At one point, you have a crossover between them, and when you bridge the gap you get a short.

This indicates to me that the two loops are wired with opposite polarity, to use the DC term, or more properly phase in DCC.  Recommended practice is to color-code your track bus and feeder wires.  I have a continuous-running layout, so I wire all the outside rails of the loop with red wires, and all the inside rails with black wires.

My guess is that you have one loop wired the other way, so that when you cross between them there is a short.  If you have separate track bus lines for each loop, try reversing the wires where one of the track buses connects to the base station.  This will flip the phase on one of the loops and should fix the short if this is the problem.

 Yes I have two loops.  One inside the other with two turnouts connecting them.  I used four wires for the buses as I had wired the layout for two power supplies before I decided to go to DCC.  Do I need to reverse the two inside wires to make the DC trains run in the opposite direction with one DC power supply?  I have a switch so I can run DCC and DC.  I burned the engine using DC last night.

Just a side note.  I tried making the making the two loops go in different directions and the same thing still happened. 

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Posted by floridaflyer on Thursday, August 12, 2010 2:50 PM

You are trying too many things at one time. As has been suggested, switch the DCC leads on one of the loops. then power up the DCC and see if the engine will pass through the turnouts. if the same short occurs then the turnout  is suspect.However you will have to trace the rails as JW suggests to insure that the polarity is correct as it may now be wrong because of the lead switch you just performed. Once you get the DCC side to run then approach the DC situation.

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Posted by maxman on Thursday, August 12, 2010 3:52 PM

If you go back and take a look at my first response to your question, I asked if you had a voltmeter.  If you don't, I suggest that you get an inexpensive one.  You can swap this or that wire until the cows come home, and you may get lucky and correct the problem.  But if you're unlucky you can end up doing to another engine what you did to the first one.

And I'm not certain what you mean by being able to switch between the DC and DCC power supplies.  There are methods out there that allow you to do this without damaging something.  But if there is a problem just getting two independent loops of track connected with a crossover, it might be time to step back and evaluate exactly what's happening.

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Posted by cgrubb80 on Saturday, August 14, 2010 7:46 AM

I found the short last night.  I did not have one of the rail insulated coming out of the turnout on the straight part.  I had the polarity correct all along.  The DCC engine now goes across the without the system shutting down.  It feels good to get this fixed.

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  • From: Orig: Tyler Texas. Lived in seven countries, now live in Sundown, Louisiana
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Posted by jeffrey-wimberly on Saturday, August 14, 2010 10:15 AM

 

cgrubb80
I found the short last night.  I did not have one of the rail insulated coming out of the turnout on the straight part.  I had the polarity correct all along.  The DCC engine now goes across the without the system shutting down.  It feels good to get this fixed.
And old man Murphy is fouled again.

Running Bear, Sundown, Louisiana
          Joined June, 2004

Dr. Frankendiesel aka Scott Running Bear
Space Mouse for president!
15 year veteran fire fighter
Collector of Apple //e's
Running Bear Enterprises
History Channel Club life member.
beatus homo qui invenit sapientiam


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