Fire in the Hole

@gunrunnerjohn posted:

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.

@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.

@gunrunnerjohn posted:

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.

@gunrunnerjohn

Thank you very much!

@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!

Would you think that was a factory installation, or an add on that someone performed? That seems even cheaper than me!!!

I have been adding little PTC’s on all cars with dual rollers. It’s a little extra work but it prevents burned, stinky wire (and LED PCB) replacements.

George

Can't speak for anyone else on this thread, but my car was straight out of the factory,  so yikes, right? Fortunately, gunrunnerjohn's easy and cheap fix works well.

Never had one go up in smoke with the PTC installed.

Hi all. It seems every time I come on the electrical forum, I learn about another device! Today it was a PTC. Lord knows how many I should know about that I don't!

@SouthCoastRocco posted:

Hi all. It seems every time I come on the electrical forum, I learn about another device! Today it was a PTC. Lord knows how many I should know about that I don't!

That's the good thing about this forum and model railroading, your always learning something new.