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Hi there!

I have an older run MTH Union Pacific Big Boy 80-3189-1 (purchased used) which I converted to SoundTraxx Tsunami2 Steam-2 sound in place of the original MTH PS3 electronics.  I never noticed it before the conversion (mainly because I seldom ran it) but now I find that the motor runs hot (I can feel the heat through the boiler shell) after ten minutes of running pulling a modest (18 car) train on level track.  It has no binds in the mechanism, nor are the wires causing drag on the flywheel or universals. 

So my question is this, could the motor not like the new electronics?


Original Post

I'm not sure about this set-up exactly. I have seen where some electronics run hot. How they handle the motor draw is part of their design, and can be their weakness. There are recent boards released that want an external fan applied to cool them!

Maybe this (Sountraxx) example is driving the motor incorrectly? Are you running it on it's correct established voltages? which model are you using?

maybe page 61 would help set-up the decoder to handle the motor better?

Last edited by Engineer-Joe


It's not the decoder which is running hot, but the motor.  The decoder is a TSU-2200.

Like I stated earlier I don't believe the problem is mechanical in nature.  I've included some photos to show why.

The first photo is a top view of the complete engine.  The heat is mainly at the rear sand box, which is right above the motor.


The second photo is with the boiler shell removed.  At the front are the double speakers (in place of the smoke unit), then the motor, and in the rear the decoder (purple thing).  The flywheel is behind the motor.


As you can see the wires are secured so they can't get into the drive or rub against the flywheel.  The third photo is a side view showing how the wires are clear of the flywheel.


In the fourth and fifth photos I have added extra insurance to make sure that the wires can't rub against the flywheel.  I added a piece of white plastic strip to help hold the wires above the flywheel.  I also removed a wire tie so the wire could spread out a bit to clear the inside of the boiler.


Finally in the sixth photo I again show a side view showing that the flywheel and wires are clear of each other.


While I can't believe that the MTH motor would have problems with the SoundTraxx decoder, I will contact George at SoundTraxx and ask him what he thinks.  Maybe there is a decoder setting that can be changed to make the motor run cooler.




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Great! I have a feeling it's some setting that might be making the motor work harder and less efficient. That's just a guess from me. I did understand that it's the motor getting hot. I also strayed off and described some other decoder brands issues. Making the company aware of any issues is helpful for others down the road.

It would be great if someone posted about the issue who has this engine with the stock MTH boards inside. If that ran hot as well, it might help us move forward.

 I do own a lot of MTH products. I don't have any of their HO line-up. Sometimes multiple posts draw more attention and get other members to chime in. So that's what I was hoping for anyways.

Last edited by Engineer-Joe

I received a reply from George at SoundTraxx regarding this issue:

Stu, it would not be the first time I’ve seen this.  The second run of the IM AC-4 Cab Forwards experienced this too.   The motors are not always the high quality motors we expect in all these models.  These had bushings that we’re expanding and restricting the shaft motion, causing the decoder and motor to run hot because it was up near stall current the whole time.  When we found out what was happening, they started a remotor plan. 
So, it would not shock me..   but no, there is not a CV that will run the motor cooler.  Sorry.  
Good luck.   

So it looks like there is nothing that can be done short of remotoring it.  I'll just run it as it is until or if the motor burns out.


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