# Marx LED headlamp conversion



## jimtone (Nov 11, 2014)

Is it possible to substitute the original lamp (1448/1449) with an LED lamp? Does this require additional wiring to convert? Can anyone verify what was the correct original lamp used in the Marx 1666 and 666 locomotives? Mine are not marked with a # but have the smaller globe which after searching I'm thinking 1448/1449 are the original style?


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## T-Man (May 16, 2008)

I can tell you a 12 volt screw bulb will work, So a replacement LED bulb fixed with a screw base and set for 12 volts will work. These types of LED replacements are made to work with AC. I would suggest just searching Marx images . I do not have any technical manual for Marx. The original lamps were probably 14 volt.

The train tender has Lionel 430-300 screw base lamps with a large globe.
One old 999 has the same style but listed as GE 428

Radio Shack has a number 52 screw base lamp with a small globe at 14.4 volts.

I believe all my simple LED headlamps on AC motors failed. I used one diode with a 470 ohm resistor. Later I went to four diodes and 1000 ohms resistors plus an added capacitor. You can check my LED threads.


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## gunrunnerjohn (Nov 10, 2010)

I believe if you use a diode, resistor, and a .47uf ceramic capacitor across the LED, you should get long life out of the LED. The issue is typically spikes that some through, the capacitor snubs them in conjunction with the current limiting resistor.


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## T-Man (May 16, 2008)

You can make that so simple, John. I would like to know if the " made to fit/replace LED would work for a headlight. Being tied to an AC motor would it last?


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## gunrunnerjohn (Nov 10, 2010)

I have no idea if the "made to fit" one would be good, I truthfully don't buy those. It's so simple to put a couple of parts together when I need an LED, that I just use discrete parts.

I think it's safe to say I have the LED Universe covered fairly well.


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## jimtone (Nov 11, 2014)

My only concerns for LED conversion is the original bulbs are not inexpensive and are easily blown. I have not heard anything simple concerning LED conversion on automobile signal lights as it requires additional grounding, capacitors or something of that nature. This is such a simple device making me guess it was the better way to go if it could be done. I'm thinking from John's description that this conversion is a bad idea if savings is the reason.


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## Kwikster (Feb 22, 2012)

jimtone said:


> My only concerns for LED conversion is the original bulbs are not inexpensive and are easily blown. I have not heard anything simple concerning LED conversion on automobile signal lights as it requires additional grounding, capacitors or something of that nature. This is such a simple device making me guess it was the better way to go if it could be done. I'm thinking from John's description that this conversion is a bad idea if savings is the reason.


The problem with the signal in an automobile is that the led's lower the current draw. The old school flasher units relied on heating of a bi-metallic strip to open and close contacts, which the led's lowered that current significantly. That conversion required a "load" to be added to replicate that draw. Electronic flashers do not have that problem. As for what you want to do, following GRJ's suggestions should work quite well for you. 

Carl


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## gunrunnerjohn (Nov 10, 2010)

The other problem with automotive lighting is that besides the bi-metallic flasher, many of the newer systems (but not new enough to support LEDs) depend on the current drawn by the incandescent bulb to sense if the bulb is blown. So, you get all sorts of oddball indication when you put an LED in place of a bulb for some systems. Since different manufacturers have different sensing systems, it's a crap-shoot if a given LED replacement will work in a specific make/model of automobile. I have a friend that was trying to replace incandescent bulbs on his BMW motorcycle with LED's, the fancy circuitry drove him crazy trying to get them to work properly.


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## DonR (Oct 18, 2012)

John

I sense that Jimtone fears complexity or expense to convert to an
LED for his Marx loco. I know it is very simple and inexpensive.

Don't you have the capability of posting a circuit drawing with the
LED, resistor and cap ratings that would show him how to do it.

Don


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## jimtone (Nov 11, 2014)

I'm not savvy about these things but willing to learn if it is a worthy project. I'm guessing it isn't worth the efforts since no ones done it from what I can see in searching??


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## DonR (Oct 18, 2012)

GRJ

Won't the LED go out when the voltage on the track gets below a
certain point? They don't just dim to dark as do incandescent bulbs.
I have 120 v LED floods on a dimmer, they'll reduce maybe 20 or 30%
with the dimmer then go out. 

Maybe a better solution to his burning out bulbs problem may be to
use a resistor or even a diode in one side of the bulb circuit to reduce the voltage
to the bulb.

Don


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## gunrunnerjohn (Nov 10, 2010)

I outlined how I'd do it, if that's not satisfactory, then I guess it isn't worth the effort.  I don't bother to try to replace a socketed incandescent, I just place the LED where I want it and secure it. Of course, I add the appropriate components as I suggested earlier in the thread.

Don, the headlight with the series resistor and diode will stay lit down to the low end of a typical PW transformer, that's around 5VAC. AAMOF, it'll be a lot brighter than the incandescent bulb at that voltage.


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## T-Man (May 16, 2008)

Marx does not offer much space. The easiest way is to buy the LED set up for a 12 to 14 lamp replacement. 

You use four diodes, one capacitor, one resistor, and the LED

The four diodes use the AC and rectifies it to DC, the capacitor helps with voltage spikes when the motor starts and stops. The resistor works ot Ohms law for the voltage difference.


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## gunrunnerjohn (Nov 10, 2010)

Why do you need four diodes? A single diode is plenty to light an LED.


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## T-Man (May 16, 2008)

John it does not last in the AC environment. I modified my 600MKT it worked for a while but the LED blew. Thinking back it did not have the capacitor so perhaps your wisdom prevails.


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## RonthePirate (Sep 9, 2015)

This interests me. I have some older pieces I would like to convert to LED's.
Could you just "pencil" me a diagram of how to wire in the diode? That's the part I'm hung up on.


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## T-Man (May 16, 2008)

The diode band ( silver ring on a 1n4001 diode)goes across the LED with the band facing the positive side. Because of AC voltage a bipolar capacitor also has to go across the LED conecctions. I uf should do it. 



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These do no show the capacitor. You need something between 750 and 1000 ohm resistor, 1/4 watt. Here you go Ron.










O f course with AC the wires connect to either rail.


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## RonthePirate (Sep 9, 2015)

Thanks, T-Man! Image saved.

Paying attention to that silver bar and the + and- of the LED.


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## T-Man (May 16, 2008)

Now with AC you can use a second LED and not use a diode. ( Well actually the second LED is a diode) 

The second LED is reverse wired, The neg side is soldered to the pos side of the first. 

Just when you thought it was simple.

Have you seen this?


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## T-Man (May 16, 2008)

For G scale you need the four diodes. Or the LED will only work in one direction.

If you click the top link in my signature, that will take you to a page of many of the old LED threads. Thinking of the MArx I would either epoxy the LED to the lamp socket or using wire insulation cover the LED leads drill two holes and epoxy the LED in the lamp socket and have it completely isolated, run two wires back where you have room. I would also rerun the center pickup from the socket to another point on the reverse unit.


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## gunrunnerjohn (Nov 10, 2010)

Correct, for dual-polarity DC, you need the bridge. If you want to suppress the spikes, you also need the capacitor. The capacitor will be most effective in suppressing spikes if it's after the resistor. The resistor is a much higher impedance than the cap to the spike, thus it's dropped across the resistor.


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## T-Man (May 16, 2008)

It is good to know but hard to imagine if you have multiple LEDs. I normally pair the resistor with the LED. It sounds practical for a headlamp replacement.


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## gunrunnerjohn (Nov 10, 2010)

If you have a filtered DC supply before it gets to any of the LED's, it's not an issue. It really doesn't matter where you drop the spikes, right?  For instance, if you have a 220uf capacitor at 60HZ, the capacitive reactance is around 12 ohms. If you have a series 150 ohm resistor before the capacitor, for instance, over 90% of the amplitude of any spike will be dropped by the resistor.


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## T-Man (May 16, 2008)

In the past I have had issues with LEDs in engines even in DC. This is the first time a pre resistor is mentioned. It makes sense, I have had luck with a Bridge because it helps with the voltage drop. My MKT is due for an upgrade. Thanks!


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## gunrunnerjohn (Nov 10, 2010)

The capacitor and bridge are normally pretty good at filtering out spikes, but if you're losing LED's, the resistor before the cap will soak up a bunch of the energy that would otherwise go to the LED.


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## 400E Blue Comet (Jul 11, 2014)

An LED lamp on a Marx train would certainly be useful, there wouldn't be much of a need to replace the bulb on an LED light Marx.


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