Friday, November 19, 2010

TCS CN in an Atlas Classic RS3

This how to page first appeared on my old web site in July of 2008.  The CN type decoders were new then but have grown in popularity as they can be used in many engines.

Refer to the photo on the left.

This type of decoder uses two PC boards which take the place of the stock LED boards.  As the front board does no have a connection to the left half of the frame, both boards are needed for the decoder to work.  I really like the design of these decoders with the tiny but bright LED and large solder pads for the wires that make re-attachment possible.
For this installation I did not have to do anything to the frame.  I started by disassembling the engine and mark the top of the motor.   Lay the front board of the decoder out as shown in the photo on the left and cut the orange and gray wires to the lengths indicated in the photo.

Refer to the photo on the left.

Remove the brush caps from the motor, then remove the contact tabs from the brush caps.  Solder the wires to the brush caps.  File a slot on the left side of the decoder deep enough for a wire to fit but not all the way through the plastic motor housing.  Re-install the brush caps, spring, and brush.  The orange wire should lay in the slot as shown.

Wrap Kapton tape around motor as shown in photo on the left.  Place motor, worm gears, and bushings into the left side of the frame.  Take care to get the motor mounts seated correctly in the frame.

Assemble the frame again taking care to have the motor mounts properly seated.  Check that the flywheels turn freely.  Plug in the decoder boards and trim the black, blue, and yellow wires to a length that will reach the rear board then solder those to the pads indicated in the decoder instructions.

With this engine the way the shell sits on the on the frame leaves just enough space for the wires.  The wires must lay flat on the top of the frame and must not overlap.  Re-install the trucks and fuel tank.

At this point we are ready for a test run.

When satisfied with the test run without the shell, the shell can then be installed.  If the shell is properly seated on the frame, the bottom of the walkways should make full contact with the 4 tabs that stick out on the sides of the frame. 

In the photo on the left the trucks have been removed to make this more visible.



  1. Thank you very much for an excellent instruction set. I was having a great deal of difficulty parsing what the TCS Instruction Sheet for the Classic CN was trying to have me do. Your instruction set description is detailed and the pictures back up the instructions really well. I look forward to referring to this blog in the future. Once again well done!

    1. Thank you for your kind comment Randy. It's always great to hear when N scalers are find this blog useful.

  2. Brad,
    I just did this CN install on the 1999 version Atlas RS3. Installation went well, and digitally, it works fine. But, the loco was a quiet runner before, and now has a annoying scream as it runs. I've swapped drive shafts, ensure gears are lubricated (not too much), and checked for any teeth damage. No luck. Any thoughts? Can something be forcing the motor out of alignment (flywheels roll freely)? Thanks. Gerry.