# USAT SD70 Questions



## acmartina (Jan 6, 2008)

My 10 yr old son got a shiny new SD70 from Santa Claus this year. It is our first USAT locomotive and I must say I am impressed. I have read over the years about their reputation for delicate details and complicated wiring and have consciously stuck with Aristocraft. It is possible that USAT have made improvements over the years but more likely I just exaggerated these flaws in my mind. I would say the detail level is a bit more than Aristocraft but not dramatically. I can see the potential for losing pieces but And the wiring couldn't be simpler. However, we did find some challenges, most of which we resolved by reading old threads here on MLS (thanks all). We still have one unresolved dilemma, and I would welcome advice and comment on how we resolved the others. They are -


Traction tires - two of the tires had fallen off an the other two were badly dried out. As a temporary fix I installed some spare LGB F7 traction tires, but after reading a number of older threads here I have concluded that we should replace the two wheel sets with regular wheels. So my question is where do you get them? I checked the usual suspects including Charles Ro website (haven't called yet). Any ideas?
Battery power - I followed Paul Norton's instructions on the OVGRS website except I left the sliders in place following advice from Greg E in an earlier post. I did actually try to remove the slides without success so I reckoned best not to mess with it! I was pleasantly surprised with the simplicity of the USA inner workings. I had read some horror stories many years ago but that must have been before they adopted the simple connectors.
Couplers - I was very disappointed in the USAT couplers. After studying Ted Doskaris' notes on Greg E.'s website, I concluded a Kadee 787 was the answer for us so I have ordered a pair. As I write this, my son is outside running it with a Kadee-equiped battery car attached by wire-tie! We will wait for the 787 before adding any more cars!!
Flashing ditch lights - My son's biggest disappointment is that the ditch lights do not flash on battery power. This seems to be a well-known problem. Eventually we will add an AirWire drop-in board. I presume that will solve the problem? Or do I need to add a separate decoder for this? Any advice is welcome.
 Thanks,
Steve H.
Cypress, TX 

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## Greg Elmassian (Jan 3, 2008)

Ordering wheels, I order wheels from USAT parts department, usually talk to Mike. 

Part numbers for the wheels are on this page: *http://www.elmassian.com...trong>**

I have not played with the ditch light circuit, but if the AirWire decoder does not have it, then get an TCS FL4 light decoder, about $14 and 4 functions, so you have ditch light and 2 more outputs to play with.


Sounds like you have learned a lot and made headway.

And I agree, while it looks like a lot of wires, the connections for the track pickups and motors are all simple 2 pin JST style connectors, and it's easy to see what is what, easier than in an Aristo.

Regards, Gerg*


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## acmartina (Jan 6, 2008)

Thanks Greg. I will give Ro a call.

I stand corrected on the ditch lights. While I was inside typing this my son determined that the ditch lights do indeed work with battery power at very low speeds (we were going too fast in our original test). We are using an Airwire (original, not G2) in a trailing car with an 18.5v Li-ion battery. Maybe it is only a problem with PWM and track power? Don't know but they do flash with this particular set-up.

Thanks,
Steve 
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## chuck n (Jan 2, 2008)

Steve:

I have an SD 70, which I run on track power. The ditch lights only flash when the engine is crawling. At higher voltages, speed, they do not flash.

Chuck 


PS Mine has neither traction tires or skates.


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## Greg Elmassian (Jan 3, 2008)

on low DC voltage the lights will flash. 

PWM is variable duration pulses of FULL voltage... when you average the power, the short duration pulses are like a lower voltage to things like light bulbs. 

They have different effects on electronics. The electronics in the flasher board see the full voltage, even on short duration pulses, and determine you are "going too fast" for ditch lights. 

You could probably put a small circuit between the motor output and the ditch light board and get it to work, like a small choke... 

Greg


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## Paul Norton (Jan 8, 2008)

Most USA trains diesels have voltage regulators for the lights that are incompatible with the PWC output of the Revolution receiver. Ordinarily the headlight won’t come on until the locomotive reaches Lionel like speeds.

Aristo-craft have recently released a board to convert the Revolution PWS to Linear DC. RLD have them under stock number CRE 57091.



By adding one of these in the MU plug wires of a power car, the locomotive should behave exactly as it does on clean DC track power. 

If they work as promised, converting a USA Trains diesel to on-board battery power and radio control will become a lot easier. With this board in the receiver's motor wires, the USA Trains circuit board can be fed linear DC power, and all the lights should work without problems. There will no longer be a need to gut the locomotive and add your own LED lights and wiring. 

I say “should” because I have not received my order, so I have not tested one yet.

Dave Bodnar has an excellent article of this board on his web site. In fact this is where I stole the picture of it because I could not find another on the web.


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