# USAT SD40-2 troubleshooting



## ewarhol (Mar 3, 2014)

All right guys, I'm in need of some troubleshooting help. I have a USAT SD40-2 with a QSI titian 10 amp decoder. Has been running great using my Digitrax 5 amp system. Only trips the breaker if I crank it up to fast, but since adjusting CV 3 for acceleration that never happens anymore. 

I replaced the tire tread wheels with solid wheels from USAT. While I was in the engine I put brass tubing pieces on the plastic gear shafts in the event those ever crack (trying to be ahead on that one). As I was putting the side frames back on I used Lucas Oil Red N Tacky #2 to grease the axle ends and journals. 

Now when I run the engine it stutters, jerks, and trips the breaker a lot. It almost runs perfect in reverse. Can't get it to move forward with out it tripping with in the first few inches. 

I did lube up the axle ends and journals pretty good. Wondering if that could be causing electrical issues. Not a good connection so the engine stutters requiring to much from the 5 amp system???

Thoughts?


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## ewarhol (Mar 3, 2014)

I was also running the engine without the pickup wipers before all this. I've put them back on, seems to help a little. Everything in the motor blocks appears fine, can't see anything that would be shorting. Didn't change anything wiring wise anyway.


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## SD90WLMT (Feb 16, 2010)

Guess I'd re-visit your drive train again...

Be certain they run smoothly on the bench.. no-load..on blocks wheels in the air kinda thing..

Did the gear box covers get placed back on carefully... are all the motor block bearings correctly positioned...

You have two issues to my thinning... 1 - erratic behavior.. 2 - overload..
These should not go hand in hand..
Unless.. a serious problem was introduced in the motor blocks...
May have to clean the red grease off.. use a lite oil.. to compare performance in the short term.. to solve your problem.

Keep after it EW

SD


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## Michael Glavin (Jan 2, 2009)

Eric

Are the bronze square axle bushings clocked and or seated correctly? Did you validate wheel to wheel gauge?

Skates will help provide an additional potential path, yet your FWD-REV anomaly has no merit herein IMO.

Perhaps the Lucas Oil product is insulating and or inhibiting conductivity between the wheel sets and side frames...

Michael


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## toddalin (Jan 4, 2008)

ewarhol said:


> All right guys, I'm in need of some troubleshooting help. I have a USAT SD40-2 with a QSI titian 10 amp decoder. Has been running great using my Digitrax 5 amp system. Only trips the breaker if I crank it up to fast, but since adjusting CV 3 for acceleration that never happens anymore.
> 
> I replaced the tire tread wheels with solid wheels from USAT. While I was in the engine I put brass tubing pieces on the plastic gear shafts in the event those ever crack (trying to be ahead on that one). As I was putting the side frames back on I used Lucas Oil Red N Tacky #2 to grease the axle ends and journals.
> 
> ...




Maybe you had a cracked axle gear and didn't realize it. Maybe one of the motors was spinning freely.

When you "sleeved" them you now put load on that motor and that now takes more current because it is actually is doing some work.

You can easily have a cracked axle shaft on the USAT engines and not realize it.


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## Greg Elmassian (Jan 3, 2008)

1. no way that loco should draw 5 amps.
2. you have an issue when it runs differently in reverse

You need to test the 2 motor blocks independently, on DC with a volt and ammeter.

Greg


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## SD90WLMT (Feb 16, 2010)

EW.. where you pulling any cars?

Greg - verify here... does a SD40-2 use the same "motor" as on the SD70mac? Eric doesn't have room to load enough cars to create such a high loading... (but - remember - I have pulled over 7.15 A on My 70mac - " measured" ....motor load only )

SD


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## Greg Elmassian (Jan 3, 2008)

Yes, the same motor blocks, different wheels I believe, not sure on the final drive ratio.

your mac pulled 7.15 amps? Clearly that was under load, not running light.

Your comment may confuse some people, since your unit is heavily modified with extra weight and all wheels have traction tires. It's not a good loco to compare to in this situation.

Greg


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## Paul Burch (Jan 2, 2008)

All my USA 6 axle locos are fused at 5 amps. No problems. Al original wiring and boards were removed and rewired with Airwire receivers, led lighting, and Phoenix P5 or P8 sound. Kind of getting away from the original subject of this thread. My guess would be that his axle bearings are not seated correctly causing a bind.


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## Greg Elmassian (Jan 3, 2008)

Something is wrong with the difference in forwards vs. reverse.

Greg


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## SD90WLMT (Feb 16, 2010)

Alas Greg... I bracketed my remarks for a reason! LOL....
I was presenting a bench mark for load, since the motors are rated @ 3.5A - each.

Eric doesn't have a layout large enough to load power as I did.
Eric has also added ballast, so his loco is closer to scale weight!

The real issue is fwd/rev dissimilarities..... which could be a worm gear bind... means looking at the idler gear installs.... are they all the same...?

SD


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## ewarhol (Mar 3, 2014)

Thanks for all the initial replies guys. 

To answer some of the questions:

- Yes the cover for the gear box was put back on correctly. Fit on nice, sealed up, did not have to force it down.
- The wheels are all gauged correctly. Used my Kadee coupler gauge to check that.
- Bronze squares were placed back in properly. I've installed them incorrectly previously and noticed the cover won't go back down, this is not the case this time.
- Engine was running solo, pulling no load. It is weighted to about 13.5 pounds. 
- While installing the sleeves I did not notice the gears/axles to be cracked. Everything looked fine. One of the new wheel sets I received from USAT had a cracked gear. I could see the silver half axle shining through. This was not the case for any of the gears/axles I worked on.
- I can test DC, but need to change CV setting that is currently set to DCC only for the decoder.


So this morning I put the engine upside down in a cradle. I disconnected the wires that are behind the front motor block. I hooked wires up to the rear skates and right to my Digitrax unit (Sorry Greg I know you said test DC and see what amps are, but I was trying to do some testing before work and didn't have time to fire up the computer and program the CV change). 

Tested rear motor block, all worked fine. Motor ran fine, wheels all spun great. Even placed a finger on them to add some load. Wheels all felt great, nice and strong. All lighting and sound features worked. So I reconnected the front block. Tested front and rear blocks together and all was fine. Placed a finger on the front wheels to add load and everything stayed just fine. Not sure why things are fine when the engine is upside down.

Tonight I will place the engine right side up on rollers and see what happens.


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## SD90WLMT (Feb 16, 2010)

Then one is left pondering......

Are any of the new sleeves binding on another part ...?

SD


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## ewarhol (Mar 3, 2014)

Not that I can see. Everything spins freely no sounds of anything binding, grinding, etc.

I have noticed that by the inner part of each motor block (where the tire tread wheels are located) that there are 4 brass rods that stick up. Each of these lead to the back of the motor where the wires plug in. 

I'm assuming the black and red wire colors don't matter. Big thing would be to keep the left rail/right rail correct. Where I'm going with this is the brass tube added for the sleeves, if that makes contact with both pins on one side could that cause a short? I'd hope a manufacturer would have thought this out in advance.


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## toddalin (Jan 4, 2008)

ewarhol said:


> Thanks for all the initial replies guys.
> 
> To answer some of the questions:
> 
> - While installing the sleeves I did not notice the gears/axles to be cracked. Everything looked fine. One of the new wheel sets I received from USAT had a cracked gear. I could see the silver half axle shining through. This was not the case for any of the gears/axles I worked on.



You can't always easily see the crack. But if you hold the wheels, you should be able to stall the motor. If it keeps spinning...


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## ewarhol (Mar 3, 2014)

toddalin said:


> You can't always easily see the crack. But if you hold the wheels, you should be able to stall the motor. If it keeps spinning...


Good to know. Thanks!


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## Greg Elmassian (Jan 3, 2008)

Sort out why it runs well on it's back and not on the track... 

Greg


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## ewarhol (Mar 3, 2014)

Turned the engine right side up. Tested it out, ok for a bit then problems started. Disconnected the rear truck wires. Everything worked fine for the front truck. Try stalling the wheels/motor, worked. 

Disconnected front truck and hooked up rear truck. Nothing but issues. I am able to stall wheels/motor. So now begins the diagnosing of the rear truck. I unplugged one of the rear truck power wires at a time. Found one of the red wires to be the culprit. Everytime I hook it up it sparks.

Could my motor be going?


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## SD90WLMT (Feb 16, 2010)

4 wires from motor block..
2 - V. supply into feed motor, from decoder
2 - v. Pick-up from rails... fed to loco entails..
Both are isolated systems...
Check proper orientation of pick-up wires.. matched to left and right rails...
..ex: engineer side may both be red..while fm side are black... 

Yet.. motor feed wires can be mixed front to rear as trucks face backwards fer rear truck - resulting in both trucks running forwards together..

SD


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## ewarhol (Mar 3, 2014)

Thing is I didn't change any wires around while working on the gear sleeves. No problems before, so why now?


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## SD90WLMT (Feb 16, 2010)

So..OK.. further along..
Remove the pick-up power leads only from the offending truck.. run on rollers or inverted here
.. ensure all wheels rotate in same direction..

You may have created a short inside the truck..based on your spark comment.. 

SD


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## ewarhol (Mar 3, 2014)

Yup Dirk it's a short..... just solved it. One of the brass wires that leads to the wiper pick ups is shorting out when it touches the brass sleeve. Results in black wire plus red wire touching the sleeve at the same time. Will post photo soon.


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## SD90WLMT (Feb 16, 2010)

Just bend the brass wire a bit to clear the brass sleeve you installed...

SD


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## SD90WLMT (Feb 16, 2010)

I was attempting to lead you towards "disturbing" something..
.. thus breaking the cycle...


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## ewarhol (Mar 3, 2014)

So the outer wires are for the motor, and the inner for the wiper pickup. Thinking if I could trim the excess brass wire for the motor that should do it. Trim it to a height it can't touch the sleeve.


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## Greg Elmassian (Jan 3, 2008)

A little confusing.

If you put a brass sleeve on an axle it should be insulated, and contacting it should cause no problem, since it is insulated.

Also, the wipers that touch the axles internally should be nearer the wheels, not the central gear.

Can you explain better what is touching what where?

In the picture below, if the sleeve on the lower right axle hit the internal pin, that could cause problems.


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## ewarhol (Mar 3, 2014)

Yup Greg, inner pins. One of the pick up skates (red pin) would touch the sleeve at the same time as the motor wire (black pin). 

Thinking if I trim the motor pin (black wire) down so that it doesn't touch the sleeve then the problem is solved. Don't know why that pin needs to be up so high anyway.


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## ewarhol (Mar 3, 2014)

I've read this somewhere on the forum before. I'll hard wire everything in the motor block. Get rid of the inner brass pins and the connectors on the backside of the motor block. 

Anyone know the wire gauge size?


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## Greg Elmassian (Jan 3, 2008)

The skates conducting to the wire or the wheel does not matter, since they are all at the same voltage.

The track pickup somehow shorting to the pins that go to the motor is a problem.

Greg


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## ewarhol (Mar 3, 2014)

Posted a fix to this issue under the following thread http://forums.mylargescale.com/39-dcc-large-scale/58058-usat-sd40-2-fix.html

Ran the engine for about 3.5 hours on Sunday, ran great, and motor sounded great. The Lucas Oil Red N Tacky #2 worked fine for greasing the axle ends.

Curious how often others grease the axle ends?


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