MTH- HOT HEADLIGHT MELTED CAB

This is the second time, on an MTH GP38 and now on an MTH SD40-2, that the headlight melted the cab. Both engines have only run for a short time in DCS. Looks like the headlight is part of the numberboard box. Anyone else experience this problem? 

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I've seen a number of melted things with the incandescent bulbs.  My fix is to swap out the bulbs for an LED with a 270 ohm resistor in series.  It drops the power dissipation to a fraction of the bulb's heat and totally solves this problem.  Not only that, but the LED's look much better as headlights.  I get a lot of units in with a request to upgrade to LED lighting, and nothing is melted on those.

gunrunnerjohn posted:

I've seen a number of melted things with the incandescent bulbs.  My fix is to swap out the bulbs for an LED with a 270 ohm resistor in series.  It drops the power dissipation to a fraction of the bulb's heat and totally solves this problem.  Not only that, but the LED's look much better as headlights.  I get a lot of units in with a request to upgrade to LED lighting, and nothing is melted on those.

Thanks John. Odd occurrence, never had anything like this happen before let alone two engines in a short time. 

 

Not with trains, but I have had cartons of the small wedge bulbs labeled wrong on the bulbs (should have been 12v, but were 6). Maybe they got a bad batch too.

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PAUL ROMANO posted:

I'll try and get l.e.d. headlights from MTH and then do some body work again. Glad its' black paint and easy to match.

You can't get the replacements from MTH, they don't do LED's for PS/2 stuff.  However, it's easy to "roll your own".  I typically use the existing headlight wiring and just cut one leg for the resistor and solder the 3mm LED on the ends of the wire in place of the bulb.

Most of the MTH passenger cars have a strip of aluminum tape stuck to the ceiling above the bulbs to reflect the heat . Strange the same is not done on the diesels. Looks like I'll be removing some shells and adding some. I really like the golden color of the incandescent headlight. Wish there was an LED that could match it. The cool blue white color of an LED  headlight just doesn't look right to me. John, do you have an outlet for an LED that looks better?

Dave

Dave, there IS an LED that matches the color of incandescent bulbs.   I have them in stock.  They're 2700K color temperature, and they look GREAT, not to mention they're far brighter than the incandescent bulb, they look like real headlights and in the correct color.  I get the flangeless LED's to replace the bulbs, they're the same diameter and no flange, so they fit where the bulbs do.

A while ago, I did a post on making an LED headlight.  The resistor value was worked out with Jason at MTH.  FWIW, none of the LED headlights I have made have failed.

LED Headlight replacement for MTH locomotives.

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Over the past years I have done many DCS upgrades.  Several people wanted bright white LEDs in headlights and backup lights.  My good friend Locolawyer is the guy I blame the most for this request.  Recently I have had members ask me to throw something on the forum instructing how it is done.  Very simple and very cheap to do.  On PS2 and PS32 boards the wires for the front headlight are light blue and purple.  Light blue coming from the number 5 pin on the 12 pin connector and the purple comes from the 2 pin on the 12 pin connector.  The rear lighting is a light green wire from pin 4 on the 12 pin connector and the purple from pin 2 on the 12 pin connector.  On front and back lighting, follow the purple wire to where your lights plug in.  The purple  is the hot wire and the corresponding wire that you need to put your resistor in on the light side of the plug.  Cut the wire and insert a 560 OHM 1/2 or 1/4 watt resistor.  Next cut the bulb off the wires and connect the longest lead from the LED to the other end of the resistor.  The long lead is plus.  Connect the other wire (negative) to the ground side and you now have LED headlight/backup lights.  I will outline this a bit better with a few pictures.

 

https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/41694216889764207/filePointer/41694216889764854/fodoid/41694216889764827/imageType/LARGE/inlineImage/true/led3%20014.JPG

 

The photo above shows left to right a section of 3/64 heat shrink, a section of 3/32 heat shrink, next a 3mm bright white LED.  This is Lionel p/n 6102045300, and a 560 OHM 1/2 watt resistor.

 

 

https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/41694216889764207/filePointer/41694216898654764/fodoid/41694216898654720/imageType/LARGE/inlineImage/true/lled4%20014.JPG

 

Above is the resistor I used.  You can buy what you need at many locations and they are very inexpensive.  No polarity is needed.

 

 

https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/41694216889764207/filePointer/41694216898654765/fodoid/41694216898654721/imageType/LARGE/inlineImage/true/led12%20019.JPG

 

 

Above is a front MTH conversion showing the light blue and purple wires used in the front headlight.  This is the original incandescent light from the upgrade kit.

 

 

https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/41694216889764207/filePointer/41694216898654766/fodoid/41694216898654722/imageType/LARGE/inlineImage/true/led4%20010.JPG

 

This shows the finished product without the shrink to show you the path of the purple wire to the resistor then to the LED.

 

 

 

 

https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/41694216889764207/filePointer/41694216898654768/fodoid/41694216898654728/imageType/LARGE/inlineImage/true/led9%20002.JPG

 

 

This photo shows the final product with heat shrink installed.

 

 

https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/41694216889764207/filePointer/41694216898654769/fodoid/41694216898654744/imageType/LARGE/inlineImage/true/led9%20013.JPG

 

 

This shows before and after.  You are out about 20 minutes of your time and about two bucks.  If you like the LED look, anyone can do it with no special skills.  The LED I used was from Lionel and the resistor from a local parts store.  You can use any manufacturer of the products.  I did some testing with these a long time ago with MTH R&D and the correct resistor we came up with was a 510 OHM.  You can go down to that if they are available to you.

 

 

https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/41694216889764207/filePointer/41694216901862971/fodoid/41694216901862966/imageType/LARGE/inlineImage/true/Locolawyer%20024.JPG

 

This is an MTH PS1 upgraded Hudson for Locolawyer.

 

 

https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/41694216889764207/filePointer/41694216901862972/fodoid/41694216901862967/imageType/LARGE/inlineImage/true/Locolawyer%20040.JPG

 

The rear of the Locolawyer Hudson.

 

 

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Marty, I'm not sure where they came up with the value of 560 for the resistor.  Obviously, you'll get plenty of light with that value, but the PWM drive to the bulb results in an effective voltage of about 6 volts.  Most common LED's have a peak forward current of 100ma or more, the roughly 20-22 volts on the PV that is PW modulated results in a peak current through the LED of less than 90ma using a 220 ohm resistor, well within the ratings of the LED.  I typically use a 270 ohm resistor for a little larger margin of error, the peak current ends up being less than 75ma, and the average current is around 14-15ma.

Can you turn the light on and off with DCS?  If not, the light control FET has shorted and your getting full DC voltage to the bulb.  That is what usually happens and than melts the shell and the bulb ultimately blows.  So check to ensure the FET is working first.  I have not really seen properly operating bulbs melt shells.   G

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GGG posted:

Can you turn the light on and off with DCS?  If not, the light control FET has shorted and your getting full DC voltage to the bulb.  That is what usually happens and than melts the shell and the bulb ultimately blows.  So check to ensure the FET is working first.  I have not really seen properly operating bulbs melt shells.   G

Thank you. I'll have to check that. The engine is at the NJ Hirailers club.

John, yes the 220 will work.   So will many others.   With Jason, time was spent to come up with that value I posted.  Bottom line, we have been doing this for years with not ONE issue.   

 

 

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GGG posted:

Can you turn the light on and off with DCS?  If not, the light control FET has shorted and your getting full DC voltage to the bulb.  That is what usually happens and than melts the shell and the bulb ultimately blows.  So check to ensure the FET is working first.  I have not really seen properly operating bulbs melt shells.   G

Thanks GGG. I thought it was the MUX board but obviously that's  not the case .    FET make more sense and I would think one  would want to get at the bottom of the problem  first.

GGG posted:

Can you turn the light on and off with DCS?  If not, the light control FET has shorted and your getting full DC voltage to the bulb.  That is what usually happens and than melts the shell and the bulb ultimately blows.  So check to ensure the FET is working first.  I have not really seen properly operating bulbs melt shells.   G

Good to know..my ps2 38's and 40-2's headlights respond to dcs command..show no signs of getting hot.

If it ain't broke,break it and make it better

Gregg posted:
GGG posted:

Can you turn the light on and off with DCS?  If not, the light control FET has shorted and your getting full DC voltage to the bulb.  That is what usually happens and than melts the shell and the bulb ultimately blows.  So check to ensure the FET is working first.  I have not really seen properly operating bulbs melt shells.   G

Thanks GGG. I thought it was the MUX board but obviously that's  not the case .    FET make more sense and I would think one  would want to get at the bottom of the problem  first.

It can be for steam engines with mux boards.  Not all engines have them though. G

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I just repaired a Premier Genesis with the headlight area deformed from the heat, and the lights were working fine, for whatever reason, the cab interior melted.  There was no issue with the lights, the voltages were all proper to the bulbs.  Sometimes the bulbs are too much for the plastic apparently.

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Somebody tell me why it's taking so long to have all LEDs in our equipment?

Anybody know why we don't have speakers in the boiler yet?

This is enough to dump O scale for me. We need a young new Mike Wolf to enter the market.

" on Sour mash and cheap wine " ??

Why go back to DCC when I have DCS!

Well, most of the new stuff is coming out with LED's.  MTH PS/3 is all LED, and the new Lionel stuff is also LED.  The passenger cars are getting LED's from the major manufacturers as well.

John, was there any rubber grommet that held the bulb in place? I would think bulbs mounted through a grommet would help insulate some of the heat from the plastic. What is also odd, is why do only some shells melt. Could it be a poor run of plastic pellets which melt at a lower temperature? Do all their plastic pellets come from the same manufacture?   Good question for Mike Wolf. He may not have any control over what brand of pellets are used or if it's recycled plastic getting into the mix.

Dave

Yes, there were rubber grommets in the holes, I took them out to put in the new cab interior that I installed.  The other piece of the cab interior had a bulb stuck right through the plastic to light the number board, and it's the one that melted the top of that piece.

If that plastic melted even with grommets, that plastic has a very low melting point. It would be interesting to know if all these Premier Genesis have this issue. Not being a plastic mix professional, I would guess that the more flexible, the lower the melting point, and the more brittle, the higher the melting point. The bigger problem we run into with harder plastic is the screw post that hold the chassis on will crack very easily. I'd much rather deal with taking precautions to prevent melting, then have to repair cracked screw post. 

Dave

Marty Fitzhenry posted:

John, yes the 220 will work.   So will many others.   With Jason, time was spent to come up with that value I posted.  Bottom line, we have been doing this for years with not ONE issue.   

There is one reasonable explanation for a higher value.  If the lighting FET does fail and put full PV voltage on it, a 560 ohm resistor would not put unreasonable currents through the LED, and you'd be less likely to have it burn out as well.

John,  agreed.  I am a big fan of LED lighting but not a fan of bright white LED's on a steam engine.  You did a post a while back talking about yellow looking LED's.    I have to admit that I was around at the end of steam and always remember looking down the track for the yellow headlight.    We are at a great place in the hobby today as LED lighting is available in all colors and shapes.  

 

 

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gunrunnerjohn posted:

I just repaired a Premier Genesis with the headlight area deformed from the heat, and the lights were working fine, for whatever reason, the cab interior melted.  There was no issue with the lights, the voltages were all proper to the bulbs.  Sometimes the bulbs are too much for the plastic apparently.

RU Sure this is not old damage?   I have repaired plenty of engines with shorted FETs where the bulb burned out and the plastic was deformed.  Installed new bulb, repaired FET and off it went.   If that was caused by a normal bulb, than every engine should have the same issue.  And the other ditch light should be deformed too. 

Problem with these post is it starts scaring every one.  Until we know of the original posters cause, all this other stuff is non factual.  The one or two off defect, is not indicative of the entire run.  G

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Marty Fitzhenry posted:

John,  agreed.  I am a big fan of LED lighting but not a fan of bright white LED's on a steam engine.  You did a post a while back talking about yellow looking LED's.    I have to admit that I was around at the end of steam and always remember looking down the track for the yellow headlight.    We are at a great place in the hobby today as LED lighting is available in all colors and shapes.  

Yep, I found some flangeless 3mm 2700K LED's, those work out perfectly for steamers.  They have a nice bright light and are the correct color temperature.

GGG posted:

RU Sure this is not old damage?   I have repaired plenty of engines with shorted FETs where the bulb burned out and the plastic was deformed. 

I can't be sure this wasn't old damage, though I was told the engine was one-owner since new and had not been worked on. Given the old battery when I opened it, I can assume it was a long time since it was worked on, if ever.

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