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How did I do this?  My Hogwarts Express passenger car 99718 started smoking for no apparent reason (I suppose the dementors could have been at their nasty work).  I run DCS with old ZW power and 10 amp fuses between track and transformer.  Never blew the fuse.  I opened the car and found this! Anyone ever had this adventure, or does he-who-must-not-be-named have my number.

Hogwarts Fire 2

Hogwarts Fire1

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Last edited by Rich Melvin
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"Sounds like a partial derailment.  Ask me how I know."

I think that we need to ask you how a short circuit at the track, and therefore between the track and the transformer, would cause a device beyond the short to burn. The short circuit, by definition, is a short route of travel for the electricity that prevents all or most of the supply voltage from reaching the load.  In a track derailment, the load (lighting board) would receive less, not more, power that it would normally receive.

@MartyE posted:

This isn't new.  My PWC Southern F3s from circa 2000 had the same setup.

Oh, I know that Marty.  I've seen quite a few with similar setups, many K-Line cars did the same thing with the pickups.  I didn't say it was unique, it's just that for a brand new car you'd think they would have finally learned the lesson!

I would think this being a fire hazard, where is the Consumer Protection Agency when we need them?

A simple 10 cent PTC would solve this problem when you design the PCB, no more fire danger!

I also have this car out of a 2007 Harry Potter set that uses conventional (non-TMCC) control.  The train sits on a display shelf and is rarely run. But the two experiences cited above are concerning to me especially when the train set is sold or passed down upon my untimely demise.  I think I'll clip power to that board and just stick in a couple of old-fashioned bayonet sockets with LED bulbs. Thanks to @Kona Girl and @Al H. for alerting us to this issue.

@Windy City posted:

Is there a proactive “fix” for this?

The fix is surprisingly simple.  Open the car and splice a decent sized wire between the two pickup rollers on the trucks, and for good measure, put a low value PTC in series with the wire, I typically use one with a 500 milliamp rating for LED lighting.  Then you cut one of the wires going to the lighting board and leave the other wire.  This allows it gets power, but the trace never tries to carry all the current from a derailment short.  The PTC protects the new wire from ever carrying enough current to get hot and burn.

Here's an example, the PTC is the brown chip in the middle, the connection to the light strip is on the right hand side.

K-Line SP Passenger LED Lighting N3

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Last edited by gunrunnerjohn

The fix is surprisingly simple.  Open the car and splice a decent sized wire between the two pickup rollers on the trucks, and for good measure, put a low value PTC in series with the wire, I typically use one with a 500 milliamp rating for LED lighting.  Then you cut one of the wires going to the lighting board and leave the other wire.  This allows it gets power, but the trace never tries to carry all the current from a derailment short.  The PTC protects the new wire from ever carrying enough current to get hot and burn.

Here's an example, the PTC is the brown chip in the middle, the connection to the light strip is on the right hand side.

K-Line SP Passenger LED Lighting N3

@gunrunnerjohn

I saw you recommend using a 500 ma current rating for PTC'S to protect LED Lighting. What voltage rating PTC resetable fuse would you recommend for conventional running of passenger car LED Lighting. I'm never over 12 Volts max on the meter while running as I have a fairly small layout with O-36 curves, so no hi-balling speed for me!  I know you recommend a much higher voltage rating for TVS Diodes, should the PTC have a rating like the TVS? I'm planning on doing some LED Lighting in Lionel and MTH passenger cars in the future, and want to do it right the first time. I appreciate your input and knowledge. Thanks!

@Gary P posted:

@gunrunnerjohn

I saw you recommend using a 500 ma current rating for PTC'S to protect LED Lighting. What voltage rating PTC resetable fuse would you recommend for conventional running of passenger car LED Lighting. I'm never over 12 Volts max on the meter while running as I have a fairly small layout with O-36 curves, so no hi-balling speed for me!  I know you recommend a much higher voltage rating for TVS Diodes, should the PTC have a rating like the TVS? I'm planning on doing some LED Lighting in Lionel and MTH passenger cars in the future, and want to do it right the first time. I appreciate your input and knowledge. Thanks!

Use something with 30 to 50 volt max rating, that covers anything you'll see on the tracks.  The 500ma is to protect the wire, it just has to be enough above the actual current draw to not be heating itself during normal operation.

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