Legacy steam engine front green marker leds keep burning out

I don’t have an answer to your question, but I have to ask this. What is an “…H7 Big Boy...?”  The model number of “H7” was used by the C&O on their 2-8-8-2 articulated engines, and the Lionel 3595 model number is one of those engines. However, the Union Pacific never used that nomenclature to describe the Big Boys.

Adding a higher rated resistor in series with the LED should clear the problem.    There is probably too much voltage going to the LED.  

prrjim  Thanks, Q, I don't see any resistors in line to the markers but maybe there is one on the board itself that has gone bad, but maybe one could be added

Rich, I don't think in real life UP ever had that term to describe any of there big boys but in the Lionel or all other manufacturers model trains are miss marked all the time. I hope that may have answered your Q   

Can anyone tell me what voltage the green marker lights are powered with on my 3595 Lionel big boy, Thanks

Green markers were only used by real railroads on loco fronts on the leading sections of a multi-section train. Unless you are running two (or three or more) section trains, you would be more accurate disconnecting the green markers at the front.

Similarly, red markers marked the rear of trains. Lots of locos have red markers lit on the tender rear. This is appropriate for the rearmost helper loco behind a caboose, but not anywhere else in the train.

These extra lights are attractive, but not accurate to prototype.

@SteamPiston posted:

Can anyone tell me what voltage the green marker lights are powered with on my 3595 Lionel big boy, Thanks

Since this unit has the RCMC logic board, the LED class lights (they're not markers) are powered directly from the RCMC.  Unless the RCMC is broken, it's incapable of putting out too much current for those LED's.

I suggest you look closely at the wiring from the RCMC to the class lights.

You can still buy other harnesses with the 2mm ceramic LED parts and fix the lights when you find out what is killing them.

Go to https://www.lionelsupport.com/ and search for class LED and you'll see the in stock choices.

You can also buy the bare LED's, but I think it'll be easier to use the harnesses to splice together new class lights.

@Ken Wing posted:

Green markers were only used by real railroads on loco fronts on the leading sections of a multi-section train. Unless you are running two (or three or more) section trains, you would be more accurate disconnecting the green markers at the front.

Similarly, red markers marked the rear of trains. Lots of locos have red markers lit on the tender rear. This is appropriate for the rearmost helper loco behind a caboose, but not anywhere else in the train.

These extra lights are attractive, but not accurate to prototype.

The green lights on the font of an engine would be classification lights Ken, …to “classify” the state of the train, ie; numbered train,  another segment, or an extra. Markers “mark” the end of a train. ie; if a locomotive is running light, moving forward,  the rear markers would be illuminated red, indicating the end of the train.

Pat

@harmonyards appreciate the correction to my inaccurate terminology

John

thanks for the post checked the wiring it seams to be ok, but when i test the output on the track the output on the RCMC Board for the class lights that voltage seams to be the same as the track voltage so if track vs are 17 vs that is what is coming from output on board so i think you are right the RCMC Board is bad. i think i can still get a board so i will get one on order tomorrow with some class lights. Thanks for the help SteamPiston

I would put an resistor in line with LED.   I suggest a small 1/3 watt one.    Start with Maybe 2000 Ohm, and if there is no light, go to 1500, or 1000 etc. until you get a light  you like that is not too bright.   If it is very bright,  you probably want a higher resistance.

@SteamPiston posted:

thanks for the post checked the wiring it seams to be ok, but when i test the output on the track the output on the RCMC Board for the class lights that voltage seams to be the same as the track voltage so if track vs are 17 vs that is what is coming from output on board so i think you are right the RCMC Board is bad. i think i can still get a board so i will get one on order tomorrow with some class lights. Thanks for the help SteamPiston

I don't know how the RCMC is putting out 17 volts, even if the driver transistor goes bad!  The transistor only has 5VDC on it, and that's put through a 270 ohm resistor!  Before you spend the money on the RCMC, perhaps we should test it?  I think something else is amiss here.

This is the drive circuit for each of the LED outputs on the RCMC.  The LED connects between the DC ground and the output on the right after the 270 ohm resistor.

LEDs are current operated, and require a ballast resistor (or other means) to limit the current.  A small LED will require about 20mA, and dissipate about 50mW.

When lit up there will be a voltage drop across the LED, and generally it depends on the LED color (more accurately the semiconductor material composition)

For RED expect 1.5V, Green (and most other colors) expect 3.0V. This is called the “Forward Voltage” (Vf)

Too much current will overheat the LED and it will fail.

The difference between the supply voltage and the LED Forward Voltage appears across the ballast resistor, which must dissipate some heat.

If there are more than one LEDs in the circuit their Vf should be similar. So any easy check is to measure each LED with a voltmeter (in the modern world a “DMM” - digital multimeter)

As this is a production item it is more likely a manufacturing fault (bad wiring, wrong value or wrong marking on the ballast resistor) and not a design mistake.

As LEDs are popular in this hobby it may help to go deeper in their care and feeding. Let me know if anyone is interested!

Peter,

@Ford Anglia posted:

LEDs are current operated, and require a ballast resistor (or other means) to limit the current.  A small LED will require about 20mA, and dissipate about 50mW.

Uhh, I think we have that covered simply by looking at the circuit on the RCMC, the 5V being directly applied through the 270 ohm resistor will result in less than the 20ma maximum current spec for the class lights.  Add to that that the class lights are in parallel, and we way below their operating current.

John

Q Is this drawing of the circuit that is on the RCMC  board if so would you check the voltage in the plug where the led class lights plug in. that would be the red led wire to ground black wire in same plug to test voltage Thanks

You have the failing board, not me.   On my RCMC testset, I have direct-wire LED's on those outputs, they are working fine.  That being the case, clearly there isn't excess voltage/current on a properly working RCMC.

John

Thanks for all your help. and for all others that have helped also.

SteamPiston

@harmonyards posted:

The green lights on the font of an engine would be classification lights Ken, …to “classify” the state of the train, ie; numbered train,  another segment, or an extra. Markers “mark” the end of a train. ie; if a locomotive is running light, moving forward,  the rear markers would be illuminated red, indicating the end of the train.

Pat

Also flags could be used on engines not as fancy as the big boy. That’s why I used to love taking the Long Island railroad to work and home every day when I lived in New York City. At Christmas time, the LIRR would run extra Trains not on the schedule when these trains would come into Penn Station. They had white flags in the front denoting non schedule train.

@SteamPiston posted:

Is this drawing of the circuit that is on the RCMC  board if so would you check the voltage in the plug where the led class lights plug in. that would be the red led wire to ground black wire in same plug to test voltage Thanks

I can help. Although I don't have the RCMC hardware. With a multimeter (DMM preferred) you can measure the voltage on your unit. Firstly, with the LEDs connected, and secondly, with it unplugged.

When connected to the PCB the red connector pin (with respect to the common or ground or the black wire) will settle to the Vf of the LEDs. Expect around two volts (2.2 - 2.6V)

Attached is a data sheet for a similar 2mm green LED (we have no way to know what part number is used in production, and it doesn't matter. Most likely these are "open sourced" from Asia)

With the connector removed from the PCB the voltage will rise to that of the supply, as there is no load and no current flowing. This should be 5V +/- 5% (4.75 - 5.25V) If it is more voltage you have found the problem, shart looking for a short on the PCB that is feeding more than five volts into the LED circuit.

If it is within expected range, reset your DMM to the current (mA) range and measure the CURRENT available from the PCB to ground (you dont have to remove the LEDs, they will go out when you probe the circuit)

Expect to see less than 10mA. If it is more you can investigate if the 270R ballast resistor is shorted or mislabeled.

You can use your DMM to read ohms across the resistor - be sure to power down the PCB first.

Hope this helps! Please post your progress.

Peter,

@SteamPiston posted:

John

Thanks for all your help. and for all others that have helped also.

SteamPiston

Have you verified your LED’s are blown? Or are you assuming they’re blown? Many times I see a break in the connection somewhere that caused them to be out. Especially if a pair is shared to the same header connector. Sometimes the way they bend and crook them to fit in the class light, or marker light housings can make the connection break. Very rarely have I seen one blown out…….99% of the time it’s a connection issue, be it a bad solder joint, or broken wire.

Pat

Pat

I'm fairly sure that they are burned out, both leds have a black spot on them, i also use a coin battery #cr2032 3v to test them my new leds light fine on this battery but the ones on the engine will not i even took leds out of the wires to test with no luck. I'm going to do some more testing on the RCMC board today just to make sure of what John is saying and that i have not made a testing mistake probably me.... Thanks

@SteamPiston posted:

i also use a coin battery #cr2032 3v to test them my new leds light fine on this battery but the ones on the engine will not i even took leds out of the wires to test with no luck.

---

   

Connecting any LED to any battery (or bench power supply or DC adapter) WITHOUT A BALLAST resistor will burn it out. Don't do it!

Note that a weak battery or one with high internal resistance (such as a coin cell) may not destroy the LED, but the risk is very high.

Peter,

@Ford Anglia posted:

Connecting any LED to any battery (or bench power supply or DC adapter) WITHOUT A BALLAST resistor will burn it out. Don't do it!

Note that a weak battery or one with high internal resistance (such as a coin cell) may not destroy the LED, but the risk is very high.

Peter,

Well... that's not really true.  Countless little toys run on 3V coin batteries with a direct connection to the LED.  The ISR of the 2032 is around 20 ohms, so it works fine for LED testing.

@SteamPiston posted:

I'm fairly sure that they are burned out, both leds have a black spot on them

There should be a paint dot to mark the anode lead side.

All LEDs are polarized and will not work "backwards" Becareful, too much reverse voltage - typically 5V or more - will kill the LED.

This is clearly noted in the datasheet (attached)

Peter,

@gunrunnerjohn posted:

Well... that's not really true.  Countless little toys run on 3V coin batteries with a direct connection to the LED.  The ISR of the 2032 is around 20 ohms, so it works fine for LED testing.

I thought I mentioned that fact in my earlier post?

"Note that a weak battery or one with high internal resistance (such as a coin cell) may not destroy the LED, but the risk is very high."

Peter,

@Ford Anglia posted:

I thought I mentioned that fact in my earlier post?

"Note that a weak battery or one with high internal resistance (such as a coin cell) may not destroy the LED, but the risk is very high."

Peter,

Exactly my point, the risk really isn't high, it's routinely done with coin cells.

In any case, since he's lost more than one LED to the problem, I don't think we're going to make progress fooling around with the LED's.  I think the top suspect is a shorted wire to the frame myself, DC ground on the RCMC is not frame ground, so any short can start popping LED's.

John

Did you by chance look at what the broad #610-1402-301 did in the circuit, all the 4 wires coming from the RCMC go to that board the gray wire that is coming from the RCMC has track voltage to it, i'm just not sure if it is a voltage regulator board or not. Thanks

@gunrunnerjohn posted:

Exactly my point, the risk really isn't high, it's routinely done with coin cells.

In any case, since he's lost more than one LED to the problem, I don't think we're going to make progress fooling around with the LED's.  I think the top suspect is a shorted wire to the frame myself, DC ground on the RCMC is not frame ground, so any short can start popping LED's.

Okay Gun Runner, you take the lead here.

In the hobby world a lot of cringe-worthy bad advice is floating around. Would hate to see more LEDs damaged. We really don't know the starting point, or the history. Unfortunately, message boards are not as efficient as some knowledgeable person standing there in person with advice. Perhaps take this to PM? I'll stand down.

Peter,

@SteamPiston posted:

John

Did you by chance look at what the broad #610-1402-301 did in the circuit, all the 4 wires coming from the RCMC go to that board the gray wire that is coming from the RCMC has track voltage to it, i'm just not sure if it is a voltage regulator board or not. Thanks

The RCMC

@SteamPiston posted:

John

Did you by chance look at what the broad #610-1402-301 did in the circuit, all the 4 wires coming from the RCMC go to that board the gray wire that is coming from the RCMC has track voltage to it, i'm just not sure if it is a voltage regulator board or not. Thanks

There is no regulator on that board.  There is a diode and resistor, that feeds the number board LED's, you'll notice they come on with track power.  All the other LED's are driven directly from the RCMC lighting outputs, see diagram below.

John will u give me a call 1801-231-9199

Thanks for that explanation that helps me a ton takes a load of the mind.

Off topic because it's the opposite problem, but I wish Lionel would do something to reduce the blindingly bright classification lights that started appearing on their engines a few years ago. I don't know what they changed, but it's a goofy - and non-prototypical - look (just my opinion, of course). If they can burn that bright, it's hard to imagine what it would take to burn them out! 

@breezinup posted:

Off topic because it's the opposite problem, but I wish Lionel would do something to reduce the blindingly bright classification lights that started appearing on their engines a few years ago. I don't know what they changed, but it's a goofy - and non-prototypical - look (just my opinion, of course). If they can burn that bright, it's hard to imagine what it would take to burn them out! 

They know and Dave Olson said that is something they are addressing.

@MartyE posted:

They know and Dave Olson said that is something they are addressing.

I would think that a couple resistors would solve the problem, it isn't rocket science to make LED's dimmer.