RailPro User Group
RailPro => RailPro Specific Help & Discussion => Topic started by: rdickson on June 08, 2025, 08:44:58 AM
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Hello,
Somewhat new to the group and just purchased RPK-2 starter kit. I'm assuming that the simplest way to go for install is look at locomotives with DCC / sound ready. After reading through several threads i'm getting the impression that Scale Trains might not play so well with Rail Pro, is that correct?
Any recommendations on what manufactures integrate well with RP?
Sorry if this have been covered before but I couldn't find any threads about this topic. Thanks for any advice.
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I just installed an LM-3S-21 in an Athearn Genesis MP15AC — no issues at all, and I’m able to access all the functions without a hitch (headlights, ditch lights, ground lights).
As far as I know Scaletrains is the only manufacturer that doesn't 100% work with 3rd party 21 pin modules/decoders. Here is a link to more info on the Scaletrains issue with the LM-3S-21: https://rpug.pdc.ca/index.php/topic,1666.msg11645.html#msg11645
I’m planning to install more LM-3S-21 modules in Rapido and Walthers locomotives soon, and based on my understanding, I don’t anticipate any major issues there either.
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Appreciate the reply Smoke, thanks for the information.
Bob
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Scaletrains definitely does not integrate well with 3rd party 21 pins. It's a known issue between ST and other DCC boards.
I can report that Rapido is a direct drop in for the LM-3S-21. Plugs right in and has access to all functions, as well as the built-in Rapido keep alive. Couldn't be any easier.
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Scaletrains definitely does not integrate well with 3rd party 21 pins. It's a known issue between ST and other DCC boards...
There was a lengthy discussion about this over at Model Railroad Hobbyist awhile back (Link (https://forum.mrhmag.com/post/scale-trains-warranty-if-you-use-a-nonloksound-decoder-response-from-scaletrains-13548862), look for Yarons posts on page 76-100 and 126-150). What it really boiled down to was all the other decoder brands aren't fully NMRA compliant and lack the required function outputs from the standard to work with Scaletrains; there wasn't anything non standard about Loksound or Scaletrains motherboards at all.
Now, the LM-3S-21 does have the required function outputs so why doesn't it apparently work in place? Mystery!
- Tim
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Great information, Thanks.
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Love to read that discussion, can you supply the link?
Interesting, the first paragraph says that the decoder is fully NMRA compliant so it's not their fault
The second paragraph then asks why the RP does not work, since it had the function outputs...
So, I'd love to read about this, so link please?
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Tim posted the link to the thread above (Link (https://forum.mrhmag.com/post/scale-trains-warranty-if-you-use-a-nonloksound-decoder-response-from-scaletrains-13548862)), but here are direct links to the posts by Yaron he mentioned:
Yaron Post #1 (https://forum.mrhmag.com/post/scale-trains-warranty-if-you-use-a-nonloksound-decoder-response-from-scaletrains-13548862?pid=1341547125)
Yaron Post #2 (https://forum.mrhmag.com/post/scale-trains-warranty-if-you-use-a-nonloksound-decoder-response-from-scaletrains-13548862?pid=1341586700)
Based on my understanding of the thread, the LM-3S-21 should offer full 21-pin functionality, including access to the ST functions. However, as Kevin’s testing has shown, certain features currently appear to be inaccessible. I wonder if there is there an update planned from Ring that would enable full functionality? That enhancement would be a significant selling point for RailPro (On top of the already great selling points).
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In the below, when I say others I mean North American manufacturers directly competing with ESU's Loksound v5 in the marketplace, this means Soundtraxx and TCS. This is pretty much the situation summarised:
- ESU makes its 21 pin Loksound v5 decoder with all outputs on the 21 pin connector available in the standard, available . The others do not. Scaletrains apparently sometimes makes use of those extra outputs.
- ESU makes its 21 pin Loksound v5 decoders in line with both the NEM and NMRA standard *. The others do not. ESU's decoders contain 4 amplified outputs on the 21 pin connector (Front/Rear headlight, AUX1 and AUX2), The rest of the outputs are logic level. The others decoders are all amplified outputs. The two types of output are not interchangeable for directly hooking up lighting.
- Scaletrains motherboards are designed for ESU Loksound and therefore are designed for NEM / NMRA standards compliant decoders.
* ESU also makes the 21pin Loksound v5 with more amplified outputs on the 21pin connector but this decoder is specifically designed for Marklin models.
The LM-3S-21 according its the documentation also follows the NEM / NMRA standard with which outputs are amplified and which are logic level, and all outputs available on the 21 connector in the standard are available. Now, as to why the LM-3S-21 is not working in place of a Loksound v5 in Scaletrains is a mystery that I can't put my hand to as I don't have any LM-3S-21's (too expensive until the exchange rate radically improves) or any Scaletrains stuff.
I feel Scaletrains has been dealt an unfair amount of bashing over this, when they were the ones compliant all along.
- Tim
Edit: Grammar
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yep, thanks for the details gents!
one niggle: a "normal" output on a decoder is an open collector transistor which conducts to minus (most people would say ground)
this "output" is either open circuit/high impedence or connected to ground
(clearly this is why the LED common is positive voltage)
a logic level output is positive when true and negative or ground when false.
open collector "outputs" can sink reasonable current, 100 ma is typical
logic level outputs can only handle a few ma, most are under 10...
but in no case would I call normal open collector outputs "amplified" they are merely a controllable switch to ground when "on"
just trying to clarify something that could be misconstrued.
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We can add Bowser to the list of locomotive manufacturers that are truly plug and play with the LM-3S-21.
The locomotives that I have personally tested and are plug and play with the LM-3S-21 are:
Athearn Genesis (MP15AC and SD60E)
Rapido (B36-7)
Bowser (SD30C-ECO)
I have been working with Tim (G8B4Life) on seeing if we can get a Scaletrains locomotive to work without any modifications and so far, no luck. We can get partial light outputs from the Ax functions, but not fully bright lights. I reached out to Scaletrains to see if they had any additional information but all I got back from support was "ESU is the only decoder that works". I did not receive a reply to my follow-up email where I included a bunch more information I have gathered.
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Great Smoke ! I Just bought a RS-3 LVRR Hammerhead, in DC/DCC ready .... going to RP it up soon.
Good to know they play well together. Did you have to change the lights out ?
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I did not change out the lights, they worked without any modifications with the LM-3S-21. The model I tested had an ESU V5 decoder so I pulled that out, replaced it with the LM and everything worked. Took a few minutes to figure out which lights went to what Ax outputs, but that's it.
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Hey All,
I just installed my RailPro system in an Athearn RTR SW1500 switcher locomotive. Damn, it's tight in there! I shoe-horned the LM-3S-21 module onto the factory motherboard and also installed a speaker with some modification to the chassis.
Has anyone installed a LM-3S-21 but removed the factory motherboard to save space? I assume there are resistors on the motherboard for the LEDs so by removing it I would have to install my own resistors? Is there anything else I would lose?
Just wondering if anyone has removed the factory motherboard or if that is a practical solution.
Thanks,
Rob S.
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I have removed the casing of the LM3S-21 to get it to fit in an Athearn Roundhouse GP40-2..
Warranty voided but it fit...and works!
Hey All,
Just wondering if anyone has removed the factory motherboard or if that is a practical solution.
Thanks,
Rob S.
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I just installed my RailPro system in an Athearn RTR SW1500 switcher locomotive. Damn, it's tight in there! I shoe-horned the LM-3S-21 module onto the factory motherboard and also installed a speaker with some modification to the chassis.
ion.
Rob - I’d be interested in seeing photos of that install if you have them. I have an SW1500 on my desk right now doing a hard install. No progress has been made on it recently due to conflicting Summer activities. Thx!
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i have had to remove the shell of the LM a time or too, as well. be sure to wrap the LM after removing the shell with Kapton tape to make sure it doesn't short out if it touches something.
i have also removed the circuit boards from loco's. as long as you mark the wires, or can trace them out so you know which is which, the circuit board is superfluous when you're using RP. if the loco in question is designed with incandescent bulbs, i would also remove those and switch to LED's with the appropriate resistors.
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fathie999: I'm confused.
Since this thread is on the 21 pin version of RP decoder... if you remove all the circuit boards, do you wire in a new 21 pin plug so you can connect to the RP 21 pin module?
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Hi Espeelark,
So here's the thing with installing the LM-3S-21 in the SW1500:
It's probably obvious that installing anything into this locomotive will be tighter than Tom Thumb's ass. I spent a good deal of time hacking up my brand-new SW1500 as I thought I didn't have a choice. I got the model WITHOUT the speaker or the default decoder from the factory because I knew I wanted to install a RailPro LM-3S-21 and my own speaker.
I had to hack up the frame a little in the front where the speaker would have come from the factory. I had to use a Dremel and file down the inside of the locomotive shell where the tabs are underneath the two exhaust pipes since this is where the LM-3S will sit. I also wanted to install Ring Engineering's version of keep-alive which is their PBM-2 module. But the only place to fit it would be inside the cab and that means removing the interior detail. It also would have been obvious that there the PBM-2 was in there through the windows.
After knocking most of the details off the shell (I will re-glue them later), I was getting frustrated that I couldn't fit the shell back on.
So I have a new approach.
I ordered a Decoder Buddy Mini from Nick Santo at NixTrainz. It will replace the factory motherboard as it is much smaller. I plan on using a few strips of styrene to build a shelf for it between the flywheels. This way, the LM-3S will sit much lower on the chassis and it might not have been necessary for me to modify the shell. Then I will see if there is room outside of the cab to install the PBM module.
I should have the Decoder Buddy Mini next week and I can approach the install from this angle.
I have a feeling that the Decoder Buddy Mini was the route I should have gone in the first place without hacking up my locomotive.
Well, you live and you learn.
I will report back one I have received the Mini and how it worked for the install.
Rob
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OK, that makes a lot more sense to me... ripping the motherboard out and NOT "replacing" the MTC21 plug would have made it impossible to connect in any "safe" way to the 21 pin decoder... in my opinion
Greg
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I just ordered a small drill press and a milling table, figured I invested a few bucks in the RP system and definitely know to fit them into most HO locos .... "Some Milling Required" - this should help the process. I've seen many dcc installs cutting frames and weights as well - so, to be expected.
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fathie999: I'm confused.
Since this thread is on the 21 pin version of RP decoder... if you remove all the circuit boards, do you wire in a new 21 pin plug so you can connect to the RP 21 pin module?
shame on me!! i responded too quickly and overlooked that significant detail! i see that in a subsequent message another member gave the right info.
sorry!
Ken