Fire in the Hole

Unless your problem was drawing more than ten amps for a while, the fuse would not open. If you wire in a fuse, inside the rail car, of the appropriate current rating for the lamp strip, and the lamps begin to emit the magic smoke, that fuse will open.

Must be those Slytherin kids at it again...

Actually, that's a classic case of a circuit frying to protect a fuse.  Only thing for it is to replace the strip.  @gunrunnerjohn makes a lovely board for constant lighting of LEDs for just such an application; drop him a note. 

Mitch

Was the car derailed? Have seen where you can do a lot of welding with a 10 amp fuse before it blows.

Sounds like a partial derailment.  A 10A slow blow fuse will allow the insulation on a small wire or circuit board trace to melt in a matter of seconds.  Ask me how I know.

With my PW ZWs I've started using AirPax Instant breakers to prevent this type of issue.

Just as an example, 26 awg is rated for 2 amps. It will melt before it ever gets to 10 amps to blow the fuse. The breakers that @SteveH cites trip instantly if I short a 26 awg wire.

"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.

I suspect that like some cars, the two pickup rollers may be wired through the lighting strip.  If one lands on an outside rail, you get smoke.

Yep, that's how it can happen.  Same sort of thing can happen to an end to end common wire if one of the outside wheels comes to rest on the middle rail.

This just happened to me today. Hogwarts Express passenger car went over a switch and shorted, but then burned for 20 minutes while we tried to pry it apart. We found that LED circuit actively burning inside the car. Had to remove it entirely.

All I can say is WOW!  You don't see that everyday!  That's what happens if they go cheap and connect the pickups through a wimpy little PCB trace!

You have to wonder why it kept burning, that doesn't inspire confidence!

@gunrunnerjohn posted:

All I can say is WOW!  You don't see that everyday!  That's what happens if they go cheap and connect the pickups through a wimpy little PCB trace!

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

@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!

Is there a proactive “fix” for this?

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.

This is fantastic.  I'll be taking this back to my O gauge group here and we will jump in.  Two more passenger cars to protect (and one to salvage).  My hands still smell like ozone.  Thanks so much for sharing this.