Installing the Train Control Systems CN decoder in an Atlas Classic RS3

July 2008

Earlier this year Train Control Systems introduced a completely new type of decoder that is in two parts, intended to replace the two LED boards that are common on many of the N scale locomotives that have required frame milling to make room for a wired decoder. Follow along as I install one of the TCS CN model decoders in an Atlas Classic RS3.
Refer to the photo above.

I wrapped Kapton tape once all the way around the motor where the brush caps are as shown in the photo. I used the tape to secure the orange wire into the groove on the left side of the motor. Then I re-assembled the components into the left side frame. Care was taken to get the motor mounting rings seated properly into the frame.
Refer to the photo above.

I then finished re-assembly of the mechanism. Again, I checked the motor mounting rings for correct fit into both frame sides. Then I plugged the two decoder boards into the frame. I found that the fit of the boards into the frame was just right and did not have to make any adjustments. Next I soldered the black, blue, and yellow wires to the rear board.

Refer to the photo on the left.

With a needle file, I filed a slot along the left side of the motor from top to bottom just big enough for the orange wire to fit into.

After stripping and tinning the gray and orange wires, I removed the brush holders from the motor and soldered the wire to them. Since there won't be any pocket milled in the frame where the brush holders are, it is especially important that the soldered connection on the brush holders be compact. No solder blobs or spikes. I used a flat jewelers file to make sure the soldered connection on the brush holders were small and smooth. I then re-installed the motor brushes.

Now on to the decoder, refer to the photo on the left.

Measuring from the back edge of the front decoder board. I cut off the orange wire at 1-3/8 inches and the gray wire at 5/8 inches. The black, blue, and yellow wires all get cut and connected to the rear board later.

Refer to photo on the left.

My habit is to always test each new decoder on my test stand before actually starting the installation.

This is not so easy to do on these decoders because components are on both boards. Also, I discovered that on the front board there is only a connection to the right frame side. The connection to the left side frame is on the rear board.

TCS offers a "goof proof" warranty on their decoders so even if you have attempted installation and have a bad decoder, they will replace it.

I started by disassembling the locomotive just like any wired decoder installation except that I left the bush retaining clips in place on the right side frame and the 4 truck contact strips.

On this model I did not do anything to the frame at all, but on some models I understand some minor frame work is necessary. Be sure to mark the motor in some way.

Refer to the photo on the left.

Now I place the shell back on the reassembled mechanism. If the wires are kept flat on the top of the frame, the shell should fit properly on the frame and rest on the 4 tabs at the bottom of the frame. In the photo, the trucks have been removed to make it easier to show.

As the couplers are attached to the shell, if the shell does not rest in the correct position then the coupler height will be too high resulting in unwanted uncoupling's.

That's it.
Refer to the photo above.

Any excess in the yellow, black, and blue wires can be folded over above the rear board. These wires should lay flat, side by side on the top of the frame.