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MTH Passenger Car Wiring up in smoke

Carl_Wicks_177Carl_Wicks_177OGR Forum Member

    Good morning, I have looked for a lead on this issue with no success, I can find tidbits. Once again I can use your invaluable advise and hope everyone is having lots of fun with their trains...

   Last night one of my lighted MTH O Premier Amtrak Superliner Dining Car decided to go up in smoke. We bought a two car set new in the box 20-6539 last month and probably have about a total of six hours of use. The consist was made of four superliner cars and one Proto-1 F59PH Diesel. We currently run the MTH engines that have not been converted to CAB-2 in conventual mode.

  Our current layout has 48' of MTH Solid three rail RealTrax Powered by a 1966 Lionel ZW that has been internally upgraded with Whistle Diodes and a fast acting circuit breaker output is set to a constant 18VAC . We have Polyswitch 30V 8Amp quickset fuses on all of the power to track leads. The lionel ZW circuit breaker nor the Polyswitch tripped, I first noticed the smoke just as I was about to cycle the train into motion and cut the power immediately.

  When I opened the car I found that there are two sets of brass rails that house two incandescent lights on the bottom and four up top and gets power from the pickups from both trucks from a red and black wire. There are no obvious shorts or signs of contact that I can see. The red power wire has melted from one end of the car to the other, the black wire is intact with no signs of damage. It almost looks like heat damage from too much current? There is no damage or signs of heat on the brass strips or the trucks, just the melted red wire.

  We have started converting all of our trains to LED. We had not planned on doing anything to the Superliner's for the time being, they are new right? - Trash that plan now mind you. The question we have is what could have possibly caused the wire to melt so fast with such a small load (my assumption) and should I install separate fuses in the train cars themselves as we convert them to LED's? For the conversions we using JW&A 20110 LED Lighting Regulators.

  Thanking you in advance,

  Carl and Susanne

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gunrunnerjohngunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

The normal reason the power wire melts is a derailment puts one center track roller on an outside rail.  If you don't get enough current to trip your circuit protection, the wire gets hot.  I put a low value PTC between the pickups in my LED upgrades, typically a couple hundred milliamps trip voltage.  Here's one thread I posted where I mentioned it.

LED Lighting Upgrade for MTH Full Dome Car

S stan2004OGR Forum Member

This OGR post in the Electrical Reference section links to a suitable PTC resettable fuse as GRJ described.

ptc

The idea being that if you already have the passenger car opened up for bulb-to-LED conversion surgery anyway, why not invest in some inexpensive insurance.

I see though that the suggested PTC is essentially a discontinued component albeit DigiKey still has some stock.  If you're planning to upgrade a fleet of passenger cars, you should be able to buy a suitable PTC for say 25 cents a piece.  I'm a cheapskate and 67 cents each at qty 10 (plus shipping) seems a bit steep to me.  One of us can track down more economical options if relevant to you.

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Carl_Wicks_177Carl_Wicks_177OGR Forum Member

    Thank you! That is a wonderful idea, perfect solution!  Also thank you for the updated part number for them John. I placed a order for enough to do all of my powered cars and a few extra. Everything happened so quickly that I can't say for sure that I hadn't bumped the train during the day setting up and testing the elevated track that Susanne needs for her pasture, it is quite possible that the car had been derailed when I turned on the track power. It makes total sense with the power traveling directly from one truck to the other POOF!!! Good bye Red Wire. I hadn't thought of that at all.

  Another question or two,

  I have installed a 30V 8A Polyswitch fuses between the Cab2 and the MTH Track Loc-On's after reading several posts about them on this forum. I also updated my 15A circuit breaker in the 1966 Lionel ZW (and tested it). Neither tripped. Is this because I shut the power down so quickly, or is it that they are rated too high for the application?

 

PingmanPingmanOGR Forum Member
@gunrunnerjohn posted:

The normal reason the power wire melts is a derailment puts one center track roller on an outside rail.  If you don't get enough current to trip your circuit protection, the wire gets hot.  I put a low value PTC between the pickups in my LED upgrades, typically a couple hundred milliamps trip voltage.  Here's one thread I posted where I mentioned it.

LED Lighting Upgrade for MTH Full Dome Car

In the Full Dome car referenced, you use two PTC's.  I'm confused since it seems in the text above you use a single PTC.  Please clarify.

Thanks.

Carl_Wicks_177Carl_Wicks_177OGR Forum Member

     I am sure John will jump in and clarify this for us,

     It looks like what He is saying is " each powered pickup truck requires it's own PTC as close to the positive supply contact point inside of the car as possible. With the powered truck PTC's you would have added protection if there were a direct short between the positive internal truck crossover wires as well as the lighting circuit. "

   Thank you for the PTC and TVS - Some Commonly Used Sizes and Part Numbers (from other threads) list rtr12

gunrunnerjohngunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER
@Pingman posted:

In the Full Dome car referenced, you use two PTC's.  I'm confused since it seems in the text above you use a single PTC.  Please clarify.

Thanks.

I put one in the frame connections between the trucks as well since the chassis is plastic and there's no connection.  You'll notice the red and black wires between them, black for wheels, red for rollers.

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