# DCC LED LIGHTS



## Cato12 (Mar 7, 2021)

I have a USA trains sd70 and I’m getting ready to install a esu loksound xl. I want to completely take out the original board and run all electronics off the esu board. As far as the led lights in the sd70 can I plug those straight into the board or do I need to had a resistor to the line? This will be my first install on a USA trains loco. Also will it be worth upgrading the smoke unit on it? If so which smoke unit should I purchase?


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## Greg Elmassian (Jan 3, 2008)

be sure they are indeed LEDs, USAT has the habit of mixing incandescents with LEDs in it's locos. They also have used 3.5 volt power supplies. You should check visually for resistors, and calculate new ones based on your DCC track voltage, which is normally higher than the DC design voltage.

I assume you have the fan driven smoke units, the ESU should be able to drive the fan and header independently, without the USAT supply board.

Here's a USAT smoke unit being directly driven from a decoder: (steam loco)






I have used Zimo and QSI decoders that drive the fan and heater directly. Have not wired up an ESU


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## Cato12 (Mar 7, 2021)

Greg Elmassian said:


> be sure they are indeed LEDs, USAT has the habit of mixing incandescents with LEDs in it's locos. They also have used 3.5 volt power supplies. You should check visually for resistors, and calculate new ones based on your DCC track voltage, which is normally higher than the DC design voltage.
> 
> I assume you have the fan driven smoke units, the ESU should be able to drive the fan and header independently, without the USAT supply board.
> 
> ...


There are no resistors. How would I check to if they are led or incandescent?


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## Treeman (Jan 6, 2008)

Cato12 said:


> There are no resistors. How would I check to if they are led or incandescent?


Reverse polarity, an LED will work one way only.


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## Greg Elmassian (Jan 3, 2008)

Unless you try the red/green "marker"/classification lights! 

By appearance, but as Mike pointed out, an ohmmeter will tell you (except those r/g LEDS)

The point is that you have to check... I can give you the tried and true, guaranteed method, but most people don't want to learn or take the time. Sorry to sound cynical, but the number of times people have asked this question, and then decided to "chance it" (and burned out lights) is overwhelming.

If you want to learn the method that works on any loco, read the bottom of this page:






F3 DCC install


Greg Elmassian web site on large scale trains and garden railroads, cigars, and computers




elmassian.com





Greg


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## Cato12 (Mar 7, 2021)

Greg Elmassian said:


> Unless you try the red/green "marker"/classification lights!
> 
> By appearance, but as Mike pointed out, an ohmmeter will tell you (except those r/g LEDS)
> 
> ...


I was able to get them to work properly without burning them out. Thank you


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