Very strange...
I suggest you get some ballast there instead of the dirt pronto!
Also, any chance it was a switch, that by being lifted, "changed it's mind"?
Anyway, happy you can run trains!
Greg
Visit my site: http://www.elmassian.com - lots of tips on locos, rolling stock and more.
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I guess I fixed it. I went out this afternoon armed with meters, plastic bags (to put under the track to isolate it from the ground), and a determination to find the problem. Put the meter on the track and all showed good. Got the train out and it ran like a champ. Go figure.
At this point the only solution I can think of is that there is dirt somewhere that has dried enough to eliminate the short. I may soak the track good with the hose and see if the problem reoccurs.
Thanks to everyone who contributed ideas, suggestions, questions, or silliness (I've had some of that in some of the forums). Your contributions are all greatly appreciated.
Tom (still scratching his head)
Life is simple - eat, drink, play with trains!
Go Big Red!
PA&ERR "If you think you are doing something stupid, you're probably right!"
Thanks for all the helpful suggestions, everyone.
When I tried to run the trains, there was a dead short. I had 16 volts to the track connector. The meter showed a complete short between the two rails. I tested the connector. It was good. After investigating, I found moist dirt touching the rails. As I cleaned out the dirt, the short starting dropping, first to about 15K ohms, and gradually decreasing as I cleaned more dirt from between the rails to finally about 500 ohms.
During this testing, there were no trains on the track and the power supply was not connected.
The rails are brass and all connections are soldered. The power supply is the one that came with the Bachman set. When tested, it showed an output of about 15 volts.
Tom
What brand of track and rail joiners are you using? If it is a brand of track with rail joiners instead of clamps, one or more of the rail joiners may have loosened or corroded, and simply lifting the track to place it on the blocks temporarily cured the problem. Is the soil wet? If the track is sitting in very wet soil, this could possibly cause a short between the rails through the soil.
You stated that when you went out to run trains - "nothing". I assume that means that the train did not move. A 500 ohm short would only cause a current draw of about 50 ma at 24 volts applied. My guess is that your train would probably have run even with that 500 ohm short.
Remove your trains, turn your power supply up full and measure the voltage at various points around your loop of track (at this point we're assuming that you're running straight DC power, not DCC). Even with a 500 ohm load the voltage anywhere on that loop should be pretty close to the voltage at the source (the power supply).
Good luck,
So….. what was the problem? What did you eventually find that was creating a short circuit? I mean, most garden railroaders have tracks "on the ground" so in your situation what was on the ground that conducted enough current between the rails to cause the short?
Thanks, Greg. I put the track up on blocks of wood so that nothing was touching the ground. As I removed the blocks of wood, I would retest the circuit. I kept removing the wood and retesting until I found the area that would cause the sort when placed in contact with the ground. I have checked the underside of the track and vacuumed away and debris.
Thanks all for your questions and suggestions. It helps me to clarify my thinking and add information that I may have overlooked.
Something is strange... the problem went away when you put the track on blocks? You mean up in the air? What were the blocks made of?
So this short is good enough that it trips the breaker on your power supply? What are you using for power?
Without knowing more, I would break the track into 2 halves, with the joiners completely out between the 2 halves, and then test... whichever half has the short, then break that in 2, etc. If you do it this way, you will find the short very quickly.
(Known as the radix search method in computers)...
Don't guess, just do it, will find the short in just a few tries.
Thanks, Walt. I did have the power supply disconnected.
fiatfan I tried to run the train the other night after about a two month absence. Nothing. Started testing with the meter and eventually found that the two rails are showing a short. I have a single loop of track. No turnouts or other wiring complications. A digital meter shows a short with about -500 ohms with the common lead on one rail. If I switch leads the meter shows open. With an analog meter I show about 500 ohms regardless of which lead is on which rail. The track has been in place for about one year. It's brass, code 332, with plastic ties. I have vacuumed the ballast out from around the area where the problem seems to be occurring. I narrowed the problem area down to this location by raising the track onto wood blocks and then removing the blocks one at a time until I found the location where the short reappeared. Some times if I move the track, the short will disappear, only to reappear a couple minutes later. I have put the meter on the track while raising the track and the meter still shows a short. If I remove the leads and retest a couple minutes later, the short is gone. I am completely stumped by this behavior. Any ideas or suggestions would be greatly appreciated. Tom
I tried to run the train the other night after about a two month absence. Nothing. Started testing with the meter and eventually found that the two rails are showing a short. I have a single loop of track. No turnouts or other wiring complications.
A digital meter shows a short with about -500 ohms with the common lead on one rail. If I switch leads the meter shows open. With an analog meter I show about 500 ohms regardless of which lead is on which rail.
The track has been in place for about one year. It's brass, code 332, with plastic ties. I have vacuumed the ballast out from around the area where the problem seems to be occurring. I narrowed the problem area down to this location by raising the track onto wood blocks and then removing the blocks one at a time until I found the location where the short reappeared.
Some times if I move the track, the short will disappear, only to reappear a couple minutes later. I have put the meter on the track while raising the track and the meter still shows a short. If I remove the leads and retest a couple minutes later, the short is gone.
I am completely stumped by this behavior. Any ideas or suggestions would be greatly appreciated.
Tom,
Did you have the power supply connected to the track while you were making your measurements? If so, disconnect it and try again.
Walt
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