I have a small layout with two loops of track joined together by 4 MTH 031 switches. I am using DCS and TMCC for control. If i run two trains at the same time the trains will run fine for about a minute and then the circuit blows. I have checked all power drops and they are fine. Does anyone have a clue why this happens? If i run only one train at a time it isnt a problem. Also if I run two on the same loop it isnt a problem eather. Any help would be great as usual.

Original Post

I was thinking lack of power, but upon rereading your post I see 2 trains run on one loop so that's probably not it. 

Check the non-derail sections of the switch (the two short rail pieces between the frog and end of the switch) to make sure that the ends are not touching the next track section.

When  you say two on the same loop are OK, is that true on either loop or only on one of them?  If so, wonder if the second loop (turned off when two on first loop) has a high-resistance short somewhere that puts an extra load on the power source when that loop is powered up.  Something tiny enough in the track, somewhere, drawing just enough current.  Tiny nail, staple, etc?  (From experience here)

I would say trying running 2 trains at the same time and let us know what your current draw is and at what voltage your inputting to track read on z4000 transformer! and what engines items number are the engines your using?

 at that time!


Last edited by Alan Mancus

You may be running near the limit with two trains, and after a minute as things warm up you exceed current limit and pop the breaker.  Get a bigger transformer.  G

I am using a PW 275 watt transformer. Do I need a Z4000? I will measure the voltage but i believe I have 18.5  volts going to the track. I have 4 power drops on the outer loop and two on the inner.

Last edited by RRAddict

Not voltage, amps. Voltage is more like "speed", amps is kinda like torque.

Drawing more amps you may have a voltage drop, but too many amps trips a breaker.  A 4a breaker can only pass 4a, be it 4a @ 12v or 4a @ 24v.

You can measure train, turnouts, and lamps alone and then add amps for total reading.

As you pass through turnouts, you may be firing two turnouts via anti-derail. (so e.g..  Turnout #1 uses 1amp, its lamp .25a #2 uses 1.2a, and .25a, Train one used 2.3a, caboose lamp .25a, Train #2 uses 3.5a.... 3.5+.25+.25+.25+1+1.2+2.3= 4.75a .... and mind you the engines might pull a couple of extra amps when first moving (split second; "peak amps" vs continuous)  Thermal breakers usually trip on a continuous average of heat so peaks if fast are ignored; modern ones trip right at peaks which can be a pita if you are close to max amo draw all the time.

Look close to see that no wheels sit narrow in gauge. If the backside rubs the wrong spot on a center rail, you may short.  Also check that no roller is hitting the top of two rails in the turnouts. Wide rollers or tilted vs level rollers can short on turnout rail tops. (Sometimes the boss where the roller axle is can hit too)

I also wonder if you have insulated the antiderail with fiber pins as(if) needed 

RRAddict posted:

If i run two trains at the same time the trains will run fine for about a minute and then the circuit blows. 

You mention using a PW ZW. Does it have the original breakers or modern replacements?

A PW ZW has no problem running 2 or more trains.  The internal breaker could be bad.  Does the layout run ok if both trains are on either loop?

RJR posted:

A PW ZW has no problem running 2 or more trains.  The internal breaker could be bad.  Does the layout run ok if both trains are on either loop?

Yes they run without a problem.

I still suspect the switches, but I don’t know why. I seem to remember reading something about insulating 1 of the rails when I had one for a spur on one of my Christmas layouts, but I can’t find where I read it. Does either train stop when you go through any or all of the switches?

In order to eliminate the switches as a possible cause, you could remove two at a time (I assume they are either in a 4 switch "X" crossover or twin two switch crossovers at different locations on the layout) and replace with straight sections and see if the issue persists.

I assume that each loop is on a separate handle?  If so, when both trains are running on one loop, do you have the other loop powered up?

Place the Lock-ons on the inner loop on opposite sides of the track (one inside, one outside) to provide a common for both outside rails.

Check the switch motors to ensure that they are properly seated. The switch instruction sheet describes how to properly remove/install them.

Finally, if someone hasn't updated the cord/plug of the transformer with a modern plug (wide blade, thin blade), try reversing the plug in the receptacle. 

If you're running two turnouts connected directly to one another I'm leaning towards @DoubleDAZ suggestion that your problem is with the turnout wiring.  IIRC Realtrax turnouts that are wired together require a jumper wire from the ground of one to the ground of the other ...possibly at the center area's frog.  When Realtrax first came out I had the similar experience of an arc and circuit break whenever a train crossed one switch to the other.  When I mentioned this to MTH (Jeff S?) at York 2001 his separate jumper wire suggestion solved the problem.

RRAddict posted:

So you are saying that i need to use a jumper from one switch to the next?

IF two of your turnouts are joined at the diverging (curved) ends (think crossover) and you're getting an arc and/or tripped breaker then IIRC yes.  I'm not certain since its been 18+yrs but I think the reason was that the Realtrax turnouts divergent ends non-derailing wiring did not have the common/ground bridged in the possibly isolated divergent ends.  The jumper was just a short basic wire connected to the outer copper tab on the underside of the straight section to the outer tab of the divergent section - you might also be able to run the jumper from the corresponding covered terminal screws of each turnout.  Can't remember if it mattered if you connected the outer rails on each of the same turnout or across from one to the other.  You can first test above the turnout w/ the jumper.

A while back @Bobby Ogage posted this related helpful pic

Thank you I am almost sure that thos is the problem. I will attemp this fix tomorrow. Should i do all 4 switches and I am guessing it is safe.

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