Decoder wire cutting guide

Here is a trick I started using years ago to make my installations more quickly and more consistent.

With wired decoders, it's somewhat critical to get the length of the wires cut to just the right length.  Once you know the lengths, you could write them down for future installations in the same type of locomotive.  What I do to save time is to make a card like the one shown in the photo.  Then I just lay the decoder wires out on the card and cut each wire to the length specified on the card with a hobby knife.

It's also a good place to make notes on the card about this particular engine or installation.  For example, on this card I have noted that the white magnet on the motor goes to the top and that this card is referring to the use of an Aztec Trackmaster TM3008 frame and a Digitrax DZ125 decoder. 

Train Control Systems CN or CN-GP ?

The Train Control Systems CN type decoder is a good choice for some locomotives where they can be installed with little or no modification to the frame.  So what's the difference between the two and where can each be used.  I've been working with these quite a bit lately and have some answers.

The only difference between the two decoders is the shape and size.  The CN is shaped to fit between the parts of the frame that stick up on both ends of the Chinese made Atlas RS and RSD series of locomotives and is slightly longer than the CN-GP.  Refer to the photo above to see a comparison of both types. 

As the name suggest, the CN-GP is designed for the Chinese made Atlas GP series.    Both of these decoders can be used in other locomotives as well, sometimes requiring a little more modification to the frame.  The table below lists all of the locomotive types that I've installed these type of decoders in so far along with brief notes about the installation.  If I have related material in this blog, there will be a link to it.  This table will be updated whenever I discover another locomotive that the CN or CN-GP decoders can be used in.

 

Make and Model	Decoder type	Notes
Atlas GP7 and GP9	CN-GP	1995-1997 releases - see instructions
Atlas SD7 and SD9	CN-GP	Old release made by Kato - see instructions
Atlas Classic RS1	CN only	Reverse board locations - see instructions
Atlas Classic RS3	CN only	See detailed instructions
Atlas Classic RSD4/5	CN only	See detailed instructions
Kato SD40 or SD45	CN or CN-GP	Requires slot on top of frame for wires
Kato U30C or C30-7	CN or CN-GP	Requires slot on top of frame for wires
Life Like C424	CN-GP	Requires slot on top of frame for wires and reverse board locations, see instructions
Life Like GP60	CN-GP	Minor frame modification, see instructions

TCS CN in an Atlas Classic RS1

For the Atlas Classic RS1 I like to use the TCS CN decoder without removing any weight from the already light frame.  As many of the steps here are the same as with the Atlas Classic RS3, I will only focus on what is different from that installation.

Normally the part of the CN type decoder with the most components goes on the end of the frame that is the forward, or short hood end.  With the Atlas Classic RS1 this would require removal of some material from the frame however the decoder boards will fit perfectly if their positions are reversed.

The photo at left shows a top view of the standard layout to help understand how the decoder defines forward and reverse.  When we swap the position of these boards it's like reversing the red and black wires of a wired decoder.

Follow all of the steps in the RS3 installation except that the main decoder board will be at the long hood end.

Connect the orange and gray motor wires as shown in this photo which will be reversed from what they normally are.

At this point when you test run this engine, it should run backwards on DCC but in the correct direction on DC. 

To correct the DCC direction program the decoder for long hood forward.  This is done by entering 07 at CV 29 for 2 digit addressing or 27 at CV 29 for 4 digit addressing.

This photo shows an overhead view with the decoder boards installed.  After programming CV29 to compensate for the main decoder board being on the long hood end, the engine should run in the correct direction in both DC and DCC modes.

If you are modeling one of the railroads that considered the long hood of the engine to be the forward end, then skip the reversal of the motor leads and the reprogramming of CV29.