# Dead Short in one track power loop when a good engine is placed on the track



## JaDaGing (May 25, 2008)

I need Help!
I have the Aristo Crest remote power control system on two separate loops, each with it's own receiver.
The lower loop is working great, however I have developed some quirk in the upper loop.
I can adjust the power with the remote and meter the same everywhere on the loop, but as soon as I place an engine on the track I loose that power.
I have disconnected all inter loop connections (they had split jaw insolated clamps)

I'm looking for any help in trouble shooting this issue....
I have tried a brand new receiver and removed sections of track, a couple switches and none of these have helped.

Any help will be appreciated.


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## Treeman (Jan 6, 2008)

Could the problem be in the engine.


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## Greg Elmassian (Jan 3, 2008)

I assume the same loco runs ok on the other loop? 

If so, swap power systems to make sure it's not a weakness in the power system. 

What is the "power system" in detail? power supply and TE or power supply and controller, ?? 

Greg


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## George Schreyer (Jan 16, 2009)

Is there high current on the bad loop? If not, suspect that your power loss is a high resistance in the wiring to that loop.


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## JaDaGing (May 25, 2008)

Thanks all for your questions...

The engines I have tried all run fine on other loops or tracks, so I don't believe it has anything to do with the engines.

I'm using Crest Train Engineer power supply and receiver and transmitter, they all work fine elsewhere on the layout.
I swapped the receiver on that loop for a brand new one with the same results.

I thought it might be a bad isolating rail clamp, but I removed an entire section of track between the two loops and it didn't help. 
There presently is to long cross over’s between opposing directions but they too have isolators that have been there for several years and don't appear to be damaged or the gap between the rails closed in any way.


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## JaDaGing (May 25, 2008)

George,

Can you explain that a little more?
I can meter track voltage around the loop that appears normal, once I drop an engine on the track I measure less than 2v
How do I check for High Resistance and is that something over time with outdoor RR we have to be concerned with?
Tx
Dan


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## krs (Feb 29, 2008)

Dan,

George wrote:

"Is there high current on the bad loop? If not, suspect that your power loss is* a high resistance in the wiring to that loop*."

From what I have read so far in this thread, the last comment by George (in bold above) seems a likely cause.


To get an idea where the high resistance is, place a know good loco at the point in the problem loop where the power wires from the controller connect.

If the voltage drops to the 2 volts or so, then the high resistance is between the controller and the connection to the track - probably a corroded connection.

If you don't see the voltage drop at that time, move the loco one track section at a time to pinpoint the high resistance which could also be a connection between the track sections.

Knut


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## Greg Elmassian (Jan 3, 2008)

The problem with a loop fed from one point is that power "comes" to any location from two directions. 

Think of the loop like a clock. Let's assume your power feed is at 6:00. 

Let's assume there is something wrong at 10:00... like a high resistance connection on one rail. 

Everything will work fine. Why? Because even with the break in one rail at 10:00, power will come from 6:00 and go to 7, 8, 9 ,10... and likewise power will go from 6, and go to 5 , 4, 3, 2, 1, 12, 11... 

Having a loop can make it hard to find the problem... (and usually it takes TWO problems to show up if you think about it) 

So, "break" the track apart, both rails somewhere, say 12:00... 

Now what happens? the track between 12 and 10 is dead... easy to find. 

Do the same here... first "break" the loop... then run the loco from the feed point to where it stops running... 

If it fails immediately, then you have a short somewhere... continue disconnecting track, say at 9 and 3... you will isolate it quickly if a short. 

If it's low voltage, then run the loco out the "ends", and maybe put on rollers... then you can measure voltage drops across rail joints with a voltmeter... note: the more current you draw, the more the voltmeter will show the problem. 

I have a set of resistors that provides an 8 amp load... I can find a "weak" connection in minutes. 

Regards, Greg


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## toddalin (Jan 4, 2008)

You could attach two jumper wires with alligator clips at the point where your power wire is attached to the loop of track. Put the other two ends of the jumpers on an engine's pickup shoes and try it out. If it works OK, the problem is in a track joint within the loop. If not, it's the wiring in between the loop and power output.


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## JaDaGing (May 25, 2008)

Thanks to all of you.... 
I will see what I can find after dinner.... 
I wasn't thinking about the power feeds to the track as being the possible problem. 
If that doesn't isolate it... 
I will check that out first and then continue to open gaps in the track until I can find the problem area.


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## JaDaGing (May 25, 2008)

Many Thanks to All.... 
I found the problem in one section's wire and it appears that the one receiver, that I thought was OK had some issues of it's own. 
Then I replaced both the wire and then the reciever, I have a fully operational layout.


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## Dan Pierce (Jan 2, 2008)

Also remember that when measuring track voltage with the Aristo 27 mhz trackside receiver that the mosfets are leaky. 

I always keep a 24 volt 33 ma lamp attached to my track. 
Eliminates the leakage as it gives a small load, and allows me to instantly know if I have a track problem, or engine problem. 
I do attach the light to the track away from the power feeds!!


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## toddalin (Jan 4, 2008)

Posted By Dan Pierce on 19 Mar 2011 10:19 AM 
Also remember that when measuring track voltage with the Aristo 27 mhz trackside receiver that the mosfets are leaky. 

I always keep a 24 volt 33 ma lamp attached to my track. 
Eliminates the leakage as it gives a small load, and allows me to instantly know if I have a track problem, or engine problem. 
I do attach the light to the track away from the power feeds!! 


I have a digital voltmeter on my control panel and when a train reaches the end of a point-to-point and stops past the diodes, the voltmeter floats up to the full voltage (~22 volts), even though it may only be 14 volts under load. IIRC, only one of my three TEs actually does this. Additionally, I have LED panel lights that tell the status of each of the 3 cabs and their direction. Sometimes, these will glow a bit when nothing is running.

As you have found, they need some load to register correctly. This spring I'll just put a Normally Off switch on the panel with a ~100 ohm resistor between the cabs and ground. Then, when the voltage is "floating" I can just push the button for an accurate reading regardless of what the trains are or are not doing.


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