# USA Trains Wiring Diagrams ?



## Del Tapparo (Jan 4, 2008)

I have an SD-70 MAC to work on. I haven't even opened the box yet, because I always do research before jumping into the fire. An on-line search produced zero results for a wiring diagram. Are there any out there? Thanks in advance.


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## TonyWalsham (Jan 2, 2008)

Chance would be a fine thing. 

Good luck.


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## Del Tapparo (Jan 4, 2008)

If I interpret that correctly, the US version of that saying would be "Fat chance of that"? 

I'm sure I will end up relying on my meter to figure things out. Just thought I would ask.


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## Jim Agnew (Jan 2, 2008)

Del, the wiring is rather straightforward. The board is well marked with light, smoke and sound sockets. I did an AirWire conversion several years ago with no problem. I also rewired the ditch lights to a Digitrax decoder attached to the Airwire board.


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## TonyWalsham (Jan 2, 2008)

Del, if all you want to do is have constant brightness, reversible lighting and voltage for smoke etc, you could always try what I do. 
Supply the onboard electronics with reversible traction battery voltage via a small DPDT relay to one of the old track pick up connectors. 
The relay coil would be controlled by the rear light wiring of your ESC. 
The lights would still blink for programming. Just not together. Rather alternately.


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## Cato12 (Mar 7, 2021)

Jim Agnew said:


> Del, the wiring is rather straightforward. The board is well marked with light, smoke and sound sockets. I did an AirWire conversion several years ago with no problem. I also rewired the ditch lights to a Digitrax decoder attached to the Airwire board.


How did you wire the ditch lights to the decoder? There is 6 wires 1 red 5 black.


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## Greg Elmassian (Jan 3, 2008)

You have to figure out the wiring on all USAT locos, no diagrams. There's different voltages, some with regulators, strange circuits.... either do as Tony suggests, or go direct to the lamps/LEDs and wire yourself... many of the locos have different bulbs depending on the 5v version or the 18v version.... usually the lower voltage lights are on the larger 0.1" connectors, and the 18v stuff is on the smaller spaced connectors but not always.

The best advice is you need to measure the voltage supplied under DC to be sure, and also search for dropping resistors on the LED lines... i found 4 different voltages for lights in one USAT loco... 

Greg


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## Dan Pierce (Jan 2, 2008)

When upgrading the USA locos to DCC I change the lights to leds with known voltage/current specs.


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## Greg Elmassian (Jan 3, 2008)

I find that the stock lamps for number boards look better than LEDs, since you need to even cover a large rectangular area. LEDs behind do not have enough "distance" to diffuse well in my experience, and one LED is not sufficient for even lighting... the long tubular bulbs work better for me. A little extra time measuring voltages and adding resistors was a small price to pay for the better appearance for me.

Greg


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