# LGB F7 A-B-A



## davemacmini (Jul 23, 2013)

I have two LGB F7A units and an F7B. One A and B unit work well together, the sound is great. When I try to hook up the second A unit, running in reverse, in an A-B-A configuration, the second A unit pulls against the first one and they do not move. Is there a special hook up cable to make this all work? I have the original manuals for both units, and there does not seem to be any special instructions that address this issue, even though there is a picture showing this configuration. I think one of the A units has an MTS decoder in it (these were used units). Could that cause this kind of problem? Both the A units work individually, just not together.


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## Gary Armitstead (Jan 2, 2008)

Posted By davemacmini on 25 Jul 2013 02:12 PM 
I have two LGB F7A units and an F7B. One A and B unit work well together, the sound is great. When I try to hook up the second A unit, running in reverse, in an A-B-A configuration, the second A unit pulls against the first one and they do not move. Is there a special hook up cable to make this all work? I have the original manuals for both units, and there does not seem to be any special instructions that address this issue, even though there is a picture showing this configuration. I think one of the A units has an MTS decoder in it (these were used units). Could that cause this kind of problem? Both the A units work individually, just not together. I have a set of LGB ABBA units, stock from the factory. All I do is put the cords between each AB unit and I get sound from both B units. AND ALL the units move in the same direction. There should be NO cable between the second A unit and the B unit. Each A unit drives its own B unit.


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## chuck n (Jan 2, 2008)

I have run the LGB F7 ABA in combo for years. I have always hooked up the 4 pin and 2 pin connectors between all units. Before you do that put the A units on the track uncoupled. Apply power. They should both go in the same direction. LGB ENGINES should always go in the same direction, regardless of which direction they are pointing. If they run in opposite directions, someone has done some rewiring in one or the other A unit. If this is the case get another LGB engine and see which direction it goes. The A unit going in the opposite direction has been altered. Chuck


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## Dan Pierce (Jan 2, 2008)

You can not run the MTS A with a NON MTS A unit. 

However you can always hook up all the 2 wire and 4 wire cables on the ABA configuration as the 4 wire cable allows the sound to come from only the A units. 

NEVER TIE 2 B units together with the 4 wire sound/speaker cable!!!!! 

Always tie the 2 wire cables as these are only track power. 


I suspect the MTS unit could have the reverse bit set in CV 29 as these engines should always run in the correct direction on DC.


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## davemacmini (Jul 23, 2013)

Gentlemen. thank you for the great replies. I have tried running the two A units uncoupled, and indeed they do go in opposite directions. It looks like I will have to go "under the hood" to see what modifications have been made to one or both of these units. Eventually I want to go with battery power, but that will take some time, and for now I will run track power.


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## Dan Pierce (Jan 2, 2008)

On the LGB motor blocks, the inner 2 wires are track power. Just swap these on both trucks to change the direction.


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## davemacmini (Jul 23, 2013)

I checked and all three units have MTS decoders in them. One of the A units had the leads from the decoder reversed so it would run backwards. I tried hooking all the decoders as to the factory spec, and when running in analog mode the A units go in the same direction, but when I go to digital mode and use the MTS system, they go in opposite directions. I reversed the connectors on one of the A units, and they run fine in MTS mode that way. THe only thing that does not work the way it should is the headlight. In one direction, both A unit headlights are on, and in the reverse direction they are both off. There is no indication in the manuals that any modification should be needed to one of the A units to run in ABA configuration, but it seems that I need to run one of the units with the wiring reversed on the decoders to make it work. Am I missing something here? I note that there are dip switches on the main board in the A units, but the manual says they should all be off to run in MTS mode, and that is all that there is in the manual about these switches.


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## Dan Pierce (Jan 2, 2008)

For DCC/MTS operation, it is the decoder that determines engine direction, not the track polarity. 
So, CV29 has a bit for reversing the engine direction. 
For MTS operation, CV29 for normal direction is set for 14 speed steps and no reverse which is a value of 4. 
Change CV29 to 5 and the engine will be reversed. 
Bit 0 is direction, off for normal, on for reverse direction. 
Bit 2 is DC operation, needs to be on for running on analog power.


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## Greg Elmassian (Jan 3, 2008)

Wouldn't this be solved by consisting when using DCC? 

The locos should be wired so they all go the same way under DC.... then reversing the last A unit will work fine (reverse polarity will make it run backwards, when it is on the track backwards) 

Consisting allows you to say that the last A unit is backwards. 

Greg


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## Dan Pierce (Jan 2, 2008)

MTS does not do consisting!! 
This is a dark ages system. 
Still to date only 14 speed steps. 
Newest decoders support extended addressing and consisting, but not the central station unless one has the MTS III system with the Massoth Navigator, and then you are still limited to 28 speed steps.


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## Greg Elmassian (Jan 3, 2008)

NONE of the MTS systems do consisting? 

ALL are 14 steps only? 

I thought there was at least one LGB MTS system that did that. 

Wow.... so there is not "pure" LGB MTS system that does consisting (of any type) or over 14 speed steps? Just asking for a definitive answer. 

Looks like it is time to buy a better system... 

Greg


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## adelmo (Jan 2, 2008)

My LGB F7s w onboard decoders run 28/128 and consist with NCE system no problem. 

Verify the LGB decoder version and ditch the MTS central station.


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## Greg Elmassian (Jan 3, 2008)

The question is about the command station being able to do consisting.... 

This is not about the decoders, it's already been established they do advanced consisting. 

Yeah, I have an NCE too, thank heavens! 

Just unbelievable to me that the MTS system does not do even simple consisting, not to mention advanced consisting. 

Greg


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## davemacmini (Jul 23, 2013)

The MTS system I have was purchased as part of a large lot of used equipment. It is version 1, with the wired mouse. As far as I know there is no programmer in the boxes of parts that I got, and even if there was one, it is made for use with a PC, which is a real dark ages computer. Yes, I'm a Mac guy! In any case, reversing the polarity where the decoder connects to the main circuit board seems to work fine, although it will not allow normal running in analog mode. I can live with that, although according to all the literature I have, decoder equipped locos are supposed to run in analog mode without modifications. I guess this situation is an exception. Is there a work around for the lighting problem? As I mentioned, the headlights are either both on or both off, because of the reversed polarity in one loco. In any case, thanks for all the great advice and knowledge you guys offer to a newbie!


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## Dan Pierce (Jan 2, 2008)

And the MTS I system is serial output for function control and can not do switches!! Engine addresses 1-9 only. 
MTS II was serial only but would address 0-22. However there was a P upgrade for parallel operation and the letter P needs to be on all system components for it to work. 
MTS III was serial and parallel, but still 14 speed steps. This system would address nembers higher than 22. 

AND the original Lenz 55020 decoder was serial only if I remember correctly. 
Decoder revisions ar eimportant as some were 14 steps such as the 55020 and 55021, but later revs did 28 steps. 
the 55027 did 28 and latest versions do 128 steps. CV 106 was the rev along with CV 7.


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## davemacmini (Jul 23, 2013)

I understand the limitations of MTS I, but I doubt if I would ever need to run more than 8 locos at once. Parallel operation would be nice, but I can also live with serial, since I eventually want to go battery anyway. I have set things up so that I can quickly switch from MTS to analog operation since many of my locos do not have decoders in them. Thanks again for the help and advice.


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