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MTS and DCC and DC track polarities?

2706 Views 14 Replies 6 Participants Last post by  Road Foreman
OK. LGB G Scale analog track polarity is reverse from NMRA and Lionel G Scale follows NMRA standards (Lionel locos run backward compared to LGB, Aristo and USA locos).

To keep harmony on my layout I have reversed the analog track polarity of my Lionel locos to match my LGB locos. So much for analog track power.

Now for MTS and DCC...

When connecting a decoder to the track contact wires for use with MTS/DCC - when the locos will continue to be run primarily on analog track power - should the decoder be wired to the track contact polarity as per the (non-LGB) decoder instructions or will that result in the loco running with reversed polarity when back on track power?

In other words do LGB and Massoth use the same track polarity with their decoders for MTS/DCC as all other G Scale decoder manufacturers?


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It is as basic as VISUAL VS TECHNICAL.

The reason I started this topic was clearly stated:

"In other words do LGB and Massoth use the same track polarity with their decoders for MTS/DCC as all other G Scale decoder manufacturers?"

All I was looking for was whether Digitrax uses the same left and right track contact polarity for their decoders as LGB and Massoth use for their decoder track contact polarity.

It is a FACT that Lionel and NMRA polarity specifications ARE THE REVERSE of LGB track polarity.

It is also a FACT that MANY people (like me) learn best by VISUAL information while others learn best by WRITTEN data. Manufacturers understand this which is why they provide pictures, diagrams and schematics as well as written instructions and manuals.

I work best with reference to VISUAL SCHEMATICS. It is difficult for me to learn from written technical information.

When it comes to my trains I am a MECHANIC (installer). I am NOT AN ENGINEER. My training in understanding electronic circuits was 45 years ago (when vacuum tubes were common and transistors were relatively new). That knowledge has not been refreshed, updated or used for at least 40 years . I duplicate and install things that others have designed and or engineered to be installed by people who do not fully understand how they do what they do but just how to make them do what they want them to do.

If someone talks to me as one engineer to another engineer, they should not be surprised if I do not understand or follow their advice.

If someone really wants to help me they should talk to me as one mechanic (installer) would talk to another mechanic (installer).

I am not trying to engineer or design anything. I am trying to install the same exact things that thousands of others have installed before me.

I simply want to know how someone else previously did what I am doing and I prefer to do as little computer (decoder) programming as possible.

I have no desire to learn any more about decoder programming than the very minimum I have to know to make a decoder act the same as it does under analog track power - but to so with multiple operators.

I don't have to understand how schematics work - just where to put the resistors, diodes and capacitors - and which ones to use.

I also don't need to learn everything about all the CV's a decoder has. I would much prefer someone to tell me to change CV (whatever) to whatever the setting I need should be.

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I had planned on going to Marty's but it is so close to the MWLSTS I will probably just go to the MWLSTS this year. It would just be too many miles in too little time for me.


Posted By Treeman on 08/01/2008 9:35 PM
Jerry are you going to make it to Marty's
Hi Greg,

I think you are right in that for someone like me who is used to the "comfort" of DC polarity it is confusing to try to "unthink polarity" to work with both DC and DCC on the same loco.

In my case I tried the proven method of swapping one lead at a time until (I thought) I had tried all combinations (not hard when there are only four wires to work with).

I was mistaken - I had apparently not tried all combinations because strangely the LGB locos ran right but all three Lionel locos I wired ran backwards in DCC. I had repeated my mistake three times with Lionel locos and never with a LGB loco.

What worked for me was to remember that with DC if the loco was running in the right direction under DC there was NO CHOICE - if I swapped the track lead - I HAD to also swap the motor lead because under DC if I swapped one but not the other there was no way that the loco would not change direction under DC polarity.

The solution for me turned out to be pretty simple - and will be easy to remember in the future:

1. FIRST - get the loco to run in the right direction under DC (analog track power) because (for me anyway) this is the easiest thing to do.

2. Next - if the loco also runs in the right direction under MTS/DCC you are done.

3. Finally - if the loco runs right under DC but backward under MTS/DCC - REVERSE EVERYTHING - and it will work and you will be done.

Track leads must remain track leads but must be reversed.
Motor leads must remain motor leads but must also be reversed.

The more I originally thought about it the more confusing it became.

I finally realized that DC is inflexible in that once the positive track lead was connected to the correct motor lead to make the loco go forward I could change which side of the decoder I could plug them into but I could/should not change their polarity with each other.

A person accustomed to finding the correct DC polarity for his locos can still use that knowledge to wire a DCC decoder once he realizes that he can swap everything for the left rail with everything for the right rail and still have maintained his original polarity.

It is perhaps less a case of who or what solution is right or wrong (they all probably work equally well) but rather finding a way that makes sense to each of us.



Posted By Greg Elmassian on 08/06/2008 11:11 PM
I had the same conversation with a friend today about "polarity"... he runs DC and DCC....
When I told him what to do if the loco runs backwards on analog (reverse the motor leads to the decoder and reverse the track pickup leads to the decoder) it threw him for a loop.
I think the issue is getting someone to "unwrap" himself from thinking about "polarity" on DCC... It's apparently difficult to do in some cases.
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Are you serious?

If I took a decoder equipped loco to the UK it would run backwards under MTS/DCC?

I knew the Brits refuse to drive on the right (and correct) side of the road :D but I never imagined they would mess with my genuine American (well OK - German) locos. /DesktopModules/NTForums/themes/mls/emoticons/hehe.gif

Gee Whiz!!!

Perhaps that is why it is not called the INMRA? :)


Posted By Road Foreman on 08/07/2008 8:29 AM

PS In the UK it is negative on the engineers side..
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