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Author Topic: A Digitrax Question  (Read 2199 times)
rustyrails
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« on: May 10, 2009, 09:34:19 PM »

I own a Digitrax Big Boy that I bought back in the mid-90's some time.  The Big Boy was the first true LocoNet system, but some place along the line, something didn't get designed quite right, because the set came with something called a Loconet Adapter mark 2 (LA-2).  The idea was to plug the the LA-2 into one of the Loconet ports on the booster, a DB100a,  and then plug the throttle/command station, a DT200, into the LA-2.  I originally thought that the LA-2 compensated for some imbalance in the command bus.  In any event the Big Boy has served honorably through a couple of layouts, but is now getting a little long in the tooth.

So, with the new layout in the works, I bought a Zephyr...lots of keen features, fits my budget.  I thought I'd create two power districts and use the DB100a from the Big Boy to power the second one, thereby reducing the load on the Zephyr, keeping heat down, etc. 

My question is:  Do I need to use the LA-2, or can I just run a cable from the Zephyr to the DB100a?  Something I read recently on the Digitrax site leads me to believe that the LA-2 is a significant part of the LocoNet interface and needs to be there.  I suspect that if the LA-2 is supposed to be in the circuit and isn't, the DB100a just won't put power on the track because it won't see the command station...but on the other hand, I don't want to accidentally let out the magic smoke, either.  Does anyone know what the LA-2 really does? 

Rusty
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pdlethbridge
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« Reply #1 on: May 10, 2009, 09:58:36 PM »

Have you checked with digitrax? They have a very good self help tech file site and very good tech help.
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rustyrails
Guest
« Reply #2 on: May 10, 2009, 10:14:09 PM »

Yup, that's where I got the idea that I maybe needed the thing.  I've always used it to connect the throttle/CS to the booster.  Just don't know about the booster to booster connection.  I'll probably end up calling Digitrax before I power up, if nobody here knows for sure.  I always try to research this stuff first.  I'm married to a retired librarian and she brought me up right.   Grin 
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #3 on: May 11, 2009, 12:49:21 AM »

The original Digitrax Challenger used a DB100a command station/booster with a non LocoNet throttle.  You could build your own throttles if you wanted and if I remember correctly, they were not much different from what you might build for a Zephyr jump throttle today.

Then came the DT200, a LocoNet throttle/command station.  It could not work directly with the DB100a unless you used an adapter to translate the LocoNet protocol to the protocol used by the DB100a.  That adapter was the LA-2.  A DB100a packaged together with a DT200 and an LA-2 was sold as a Big Boy system.

All of that would seem to indicate that plugging a LocoNet cable into the Zephyr and the other end into an LA-2 would do the job.  But unless Digitrax tells you that you can do so, don't do it!

You would be better off to put together a BC-2 cable to do this job.  Details of this cable can be found on page 28 of the following link:
http://www.digitrax.com/ftp/Challenger%20Manual%20CT4.pdf

The left side of the diagram is the end of the BC-2 cable which plugs into the DB100a acting as a booster.  The right side of the diagram is the end that plugs into your Zephyr.  I assume that red and green are the colours in a standard six wire LocoNet cable that go to the Zephyr's sync and ground, but check this against the pinout diagram in your Zephyr manual.

I assume you are already aware of the requirements for interconnecting the grounds of the Zephyr and DB100a and for using separate power transformers.

Jim 
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rustyrails
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« Reply #4 on: May 11, 2009, 09:11:22 AM »

Jim,
Thanks for your input.  I had not looked at the Challenger manual because the DB100a operates differently (it is the Challenger command station) when part of a Challenger set than it does with the DT200 as a Big Boy set.  I'm going to call Digitrax in the next couple of days and I'll let you all know what I find.

I thought I had this figured out until I read a statement on the Digitrax site that the LA-2  functionality is incorporated in all subsequent boosters.  That seems to indicate that I need to use it with a DB100a on LocoNet.  On the other hand, there is a diagram that shows the DB100a directly connected to other boosters--all of which are DB100a's since that was the only booster Digitrax was making at the time.  The same diagram seems to indicate that the LA-2 is a part of the command bus.  sheesh

I really don't have to do this.  I just didn't want to waste the DB100a.   Huh?
Rusty
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Jim Banner

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« Reply #5 on: May 11, 2009, 11:20:12 AM »

The Challenger manual is the one that explains everything the DB100a can do - command station with booster, straight booster, intelligent booster, multiple boosters, you name it.  It even has the wiring diagrams for how to do all these things.  If you still have your original documentation that came with your Big boy, you may well find that it is a Challenger manual plus a DT200 manual.

You are right that one of the uses of a DB100a was as a straight booster in a Big Boy set.

Jim
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rustyrails
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« Reply #6 on: May 11, 2009, 11:49:01 AM »

I love thought problems, but sometimes you just have to go to the horse's mouth.  Here's the hot skinny from Digitrax.  The Zephyr and the DB100a are to be directly connected by Loconet cable.  The purpose of the LA-2 was purely to connect the DT200 throttle/command station to the booster.  I didn't ask, but I suspect the LA-2 compensated for an omission in the DB100a's command bus design since no other boosters have ever required it.  
Rusty
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #7 on: May 11, 2009, 06:43:42 PM »

Rusty, I am glad you got a straight and easy answer from Digitrax.  The first Digitrax I ever installed was a Big Boy with a "Challenger" booster (the DB100a.)  I thought I remembered how all that worked, but maybe I didn't understand it correctly even at the time.    But I did get decoders installed and the whole thing working.  And it was absolutely fascinating for an old block wiring type of guy to see two locomotives running on the same track at the same time, both under completely independent control.

Looking back, the technology looks antiquated.  I wonder how today's latest and greatest will look 10 years from now.

Jim 
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Growing older is mandatory but growing up is optional.
rustyrails
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« Reply #8 on: May 11, 2009, 07:00:25 PM »

Well, it turned out like I hoped...but was by no means certain.  DCC is cool, no doubt about it.  My aging bones especially appreciate not having to spend sooooo much time under the layout pulling wires.  And this layout has the benchwork much higher which helps, too.
Rusty
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