# MTH SD70Ace Color Code of Wires



## D&J Railroad (Oct 4, 2013)

I have an MTH SD70Ace HO scale that I would like to install a Tusanami 1000 sound decoder in. I completely removed the original board that was in the loco and clipped the connectors off all the leads.
I have the pick ups and motor wired and operating. The sound is wired up and sounds great. Now to connect the lights, I need to put some resisters in line with the lighting leads off the decoder.
What value of resistor should I be using here so I don't burn out the LEDs and which lead is common for the head light, tail light and ditch lights?


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## DonR (Oct 18, 2012)

Most decoders offer 12 vdc for head and backup lights.
The resistor depends on the type and
amperage of the lights. So get back to
us with what type and voltage bulbs you will be using.

Don


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## D&J Railroad (Oct 4, 2013)

DonR said:


> Most decoders offer 12 vdc for head and backup lights.
> The resistor depends on the type and
> amperage of the lights. So get back to
> us with what type and voltage bulbs you will be using.
> ...


I will be using the LEDs that are already built into the model.
I'm thinking a standard 540ohm resistor for each light should work and it doesn't matter which wire its on. I can step the value down to 270ohms if the lights aren't bright enough.
I need to know which wire is common for each of the LEDs so I can get the right polarity off the sound board.


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## golfermd (Apr 19, 2013)

That size of resistor should be fine. If the light is too bright you can always increase the Ohm value.


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## D&J Railroad (Oct 4, 2013)

Haven't got a response as to which wire is common on the LEDs, so I decided to do some probing.
I wired up the rear light with common to one lead and a 470ohm resistor in line with the power lead from the decoder then put it on the track. Nothing. I reversed the wires and the LED lit up with the loco in reverse.
I tried the same with the headlight and got that one working.
The ditch lights have me stumped though. The LEDs are polority sensitive. If I wire them individually to their F5 and F6 function lead off the decoder they don't light up, but if I wire them to the blue common lead off the decoder and one of the power leads to the common lead for the ditch light board, they will light up. The problem with this set up is that I can't set up the alternating ditch light function with the horn.
Does anybody know how to get around this problem?


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## golfermd (Apr 19, 2013)

Blue wire for the common.

http://www.soundtraxx.com/manuals/tsuinstallation.pdf


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## rrgrassi (May 3, 2012)

Download the diesel Tsunami Owners Manual. You have to program F5 and F6 to be on. There are instructions on how to program the flashing ditch lights, and then stay on or turn off with the horn button.


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