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# Truck Shay-Max DCC Voltage

Started by wedressler, February 14, 2007, 07:24:07 PM

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Has anyone had sucess in operating the Sountraxx version  of the new Shay using MTS. I've heard that people get a flashing headlight at the higher voltage ( about 23V DCC). I understand a possible fix is to reduce the voltage with diodes on the track pikcups but have yet to hear whether this works. I sure there are lots of of others ( potential customers) that would like to have a  confirmed answer on a fix.

Bill Dressler


21 volts.
And that is on DC or dcc.
MTS is 23.8 or so, right?
Gotta put a diode set on the input.

BTW, out-of-the-box, on DC, 8.5V starting voltage, 21V shutdown.
That gives you a 12.5V range.
And, any other locomotives on the track will run into the back of this before it even starts to move.


Thanks, that is what I've heard. I've seen some circuit diagrams on Tony's  Trains website but am a little confused by differences on the text explanation  and the diagrams. The text says 1 or 2 diodes , the diagrams show 2 or 4 in what looks to be a bridge rectifier arrangement. I've also heard discussion about the possible need for high speed diodes.

That is why I'd be interested to hear of someone's success with this, and installation specifics. Its more of an observation than a gripe, but  one would think the mfgrs would follow thru on compatability issues to increase thier potential market base. Seems like all of the  DCC players have a myopic focus on thier own niche market and make the buyer "worK' in order to obtain compatability with  another system. ESU appears to be an exception , however. I may avoid the Shay issue by installing a Loksound decoder in the non-sound version.

Bill Dressler


I don't know if "high-speed" or "high-current".
Use a 10 or 15 amp bridge.
As far as manufacturers following through on compatibility issues, Soundtraxx meets nmra conformance standards.
MTS does not.

So, to get your non-compliant system to work with stuff that is requires a work-around on your end.

A very interesting read is the "conformance warrants" on the nmra website.


It was high speed diodes that were reccomended, for technical reasons I didn't fully follow. With regard to NMRA, MTS does now comply. I understand there is 27V tolerance limit for large scale, but no operating voltage standard. My point is that while compatability issues may easily be blamed on the "other guy", manufacturers, especially those now offering locos with installed decoders, could greatly enhance thier marketing opportunity by helping ensure compatability. Many potential CUSTOMERS may not have the skill, or interest in jury-rigging to enable operations on thier system. Surely if someone develops an attractive product, they want to ensure as many people as possible  would consider buying it.

Thanks for the prompt feedback on my questions

Bill Dressler


No, the consumer must insure the product they are purchasing conforms.
Soundtraxx and Bachmann do.

2.2.1.  Command Station output signal
A bipolar signal must appear differentially on a two-wire cable with a signal amplitude of no less +-8V and no greater than +-22V.

And, you might want to read this:

The max is 24v, if I recall.
The minimum spec I've been told is 21v on the track, and Soundtraxx meets that.

The issue you have needs to be taken up with Soundtraxx about voltage.
Bachmann doesn't build them, Soundtraxx does.

And, as I've said before, if the consumer doesn't know what to do, they need to either learn or not do it.

The posts of folks wanting to know how to remove a shell, then install a decoder, is mind-boggling.
If someone hasn't the skill to take a shell off, they need to learn how.
Asking is fine, but to ask both at the same time is beyond me.

Like newbies wanting to know how to edit their registry.

At 23.8v on MTS, they are pushing the 24v max anyway.
In electronics, you never want to be that close.

All this is what I've read and been told, and even after 40 years in electronics, I am NOT INTERESTED in ANY KIND of dcc control.

If I want to run trains, I want to run and not mess around with a freaking computer or setting CV's.

I want to know where the wire goes, what the max current is (try to find out THAT information on OEM stuff) and something easy to fix.

In 15 years, guess how many radio control units I've had to rip out because they failed?


If one does read the DCC Standards and RP's I believe you will find that the decoder is required to withstand 24 vols for N or Z scale and 27 volts for the larger scales. Standard 9.1 Page 3 Lines 70 to 72.  If a manufacture does not meet the standard then they need to let the user know.

Most DCC decoders are not designed to run on other then DCC or DC, and a number are designed to run on DCC only.  All the DCC manufactures I have come across state if they can work on DC in the spec sheets they put out.  Running a DCC decoder on MTS has not been something that most DCC manufactures have even thought about, and I am sure that MTS does not worry about how the DCC decoder works, they only care how the equipment they have designed for the MTS system works.  They are two competitive systems and there is no need for either one to 'play nice' with the other.

As for using DCC, I do not use it because it is 'a computer', but because it is one of several available ways to run several trains on one track in different directions at one time.  It allows me to 'run my train' and not worry about controlling power.

The only thing you have to 'set' is the locomotive address.  Most systems allow you to do this with a minimum 'learning curve'.  If you wish to 'fine tune' from that point, then you can take the time to learn how to make the changes on step at a time.

Each system, DCC, MTS, DC, Radio Control, Live Steam has its good points and bad points.  It took me a while to understand how to wire a DC layout when I first got into model railroading.  I found that as I got into more complex layouts putting in the wires was taking up more and more time.  DCC has allowed me to take less time in the building stage and get to running trains.  The same could be said of Radio Control, MTS, and Live Steam.

This does not mean that DC is bad, or wrong, or 'old fashion', just that is one of many ways to enjoy the hobby of model railroading.



WITHSTAND is not operate.
Two different things.
To withstand a voltage witout smoke is totally different.


A good deal of DCC users have a track voltage of between 20 and 22 volts DCC.

The DCC standards call for a max track voltage of 22 volts DCC.

The Bachmann 3 truck Shay (like all Bachmann sound on board products) will shut down with a DCC voltage of greater then 21 Volts DCC.

if you have an MTS system you likely will have to lower the DCC track voltage depending on what input voltage you  are providing.

The above link shows how this is easily done.  For Large Scale simply use higher amperage rectifiers. It does not make any difference if these are high speed or low speed diodes, any rectifier of suitable amperage will work just fine.

If like me your DCC track voltage is within spec but higher then the 3 truck allows then you can use the same trick but this time the rectifier is placed inside the shay.

Install one on the red or black wire before the decoder and all should be fine.

Stan Ames