How To Install A Decoder

A key component to Digital Command Control is the mobile decoder.  This is the means by which the DCC system communicates with each locomotive on your layout.  With that said, it is then necessary for each engine to have a decoder.  In the past very few were factory installed, which is not the case today.  Rather, the reverse is more commonplace today, because of the increasing importance and popularity of this type of system.  However, many model railroaders have older locomotives that require the installation of this component.  

The good news is that this process, although somewhat time consuming (approximately thirty to ninety minutes), is much easier than most modelers think.  Given, that time is one of our more precious commodities, the following information will assist in reducing this task to the minimum time requirement, and in general make your work much easier:

If you’re modeling in HO scale, most manufacturers either include factory installed DCC decoders in their locomotives, or they offer an easy way to install one by using plugs.  

N scale modelers, however, are not quite as lucky.  Though more manufacturers are currently offering N scale locomotives with factory installed decoders, the vast majority of engines which are available in the marketplace require some modification to isolate the motor and include space for the decoder.

Having said this, the information which follows applies to the installation procedure for both N and HO scale.

Step 1.  Although this advice is something that most hobbyist will do, it is still worth mentioning.  Take the time to inspect your engine and make sure that it is running well.  If you have a test track on your workbench which is run on DC current this is best to use.  Should you discover a problem, the issue needs to be isolated and corrected before converting your engine to DCC.  

Step 2.  This is also an obvious step in the process which is to remove your engines shell.  However, the removal process can vary from one manufacturer to another.  Because of this, it will be necessary to have a parts diagram to use as a guideline.  

When you remove the shell you’ll find one of two things:  There will either be a circuit board which was factory installed or there will not be one.  If the former applies there will most likely be a plug which will accept a plug-in decoder and the installation is much simplified.  If the latter applies, you’ll have to remove the board to provide ample room for the decoder.  Incidentally, the circuit board is wedged in between the two halves of the frame.

Also, if you’re modeling in N scale and are able to use the drop-in method, you’ll be able to simply plug in your decoder , and this can be done in just a matter of moments.  Additionally, if you are able to use this method both Lenz and Digitrax make decoders for N scale models and are solid recommendations for your purchase.

Step 3.  Next, it’s necessary to isolate the motor itself, and this can be accomplished by isolating the motor from the frame by using regular old duck tape.

Step 4.  There are a number of wires which you will have disconnected initially, and the next step will require that you reconnect all of the wiring and when you do so, make sure that the appropriate color wiring is reconnected to the correct locations.  This also includes reconnecting the motor leads, headlights, and any additional features which your locomotive may have.

Step 5.  Finally the last step involves reattaching the shell, and when this done it’s time to program the decoder.  To do this, simply follow the instructions which are provided by the manufacturer.

If in fact, you’re not able to use the drop in method, which can be the case with some locomotives, the frame will have to be modified to electrically isolate the motor.  After completing this modification, you would then wire the decoder in place using soldered connections.  Thanks to Aztec manufacturing, this isn’t as difficult as it sounds.

For a small fee, Aztec will mill a space for a decoder in your locomotive frame and isolate the motor.  Simply visit this companies website and the follow their instructions.  They’ll want you to mail them your locomotive, and their service is relatively quick (approximately ten days).  Unlike using replacement frames once the milling is finished, your still using your locomotives original frame.  What this means is that the motor and gears will fit properly.

Aztec also includes the decoder installation instructions with each milled frame, and this also includes information for cutting the decoders wires to the correct length.  Digitrax, Lenz, and the NCE Corporation all make decoders which work well in this type of application. 

Just click on the links which are to the right of each image to download your free kit

Small Country Petrol Station

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Platform Foot Bridge

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Fire Station

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