Brad's N Scale Station - Installing a Train Control Systems M1 decoder in an Atlas Classic RS1

January 2008

The recent Atlas models of the SD24 and SD26 road switchers are the latest of many models that are made to use a standard board style decoder produced by Digitrax, Lenz, North Coast Engineering, and Train Control Systems. The models that come equipped for DCC have the Lenz decoder in them. This design has been around for about 8 years now and there have always been some problems maintaining a reliable contact between the decoder board and the contact tabs that are attached to the motor brush mountings. I have even seen the standard LED boards have this problem. My solution up to now has been to connect wiring between the contact pads on the decoder and the motor contact tabs as presented on this web site in 1999.

Refer to photo 3 above.

The stock LED board in most cases is also too thin to be a snug fit on the frame. Notice in the photo how the original LED board has solder applied to the contact points to add thickness. The same can be done with the decoder board. Measuring with a caliper indicates that a thickness of about .030 inches is about right.

Refer to photo 5 above.

Guide the two motor contact tabs through the slots as you install the decoder board on the right half of the frame. Then install the left half of the frame and secure the two screws. The tab closer to the left side may be too long and may need to be cut where the yellow line is in the photo. Bend both tabs over toward the centerline of the locomotive. This should make a reliable contact but if you really wanted to, it would be easy to solder the tabs to the decoder board at the slots.

This procedure will be the same for any of the Atlas engines that will use this latest version of the Digitrax DN163A0 DCC decoder. END

Refer to photo 2 on the left.

You will need to remove the shell of the engine and separate the two half's of the frame by removing the two screws. Keep the motor attached to the left side of the frame.

These decoder boards sometimes are a loose fit in the frame. Test fit your decoder board on each side of the frame as shown in the drawing.

Refer to photo 1 on the left.

Recently I had received several Atlas SD24's along with Digitrax DN163A0 decoders that needed to be installed in them.

I was pleasantly surprised to find that Digitrax had re-worked the DN163A0 to include small slots were before there had just been contact pads. Here is a close up of the top side of the decoder board. The plating that includes the contact pads on the bottom extends up through the slots and around the edge of the slots on the top. By placing the motor contact tabs up through these slots, a reliable contact can be made and the tabs cannot move around.

Refer to photo 4 on the left.

After you get the fit of the boards contact points adjusted straighten the motor contact tabs to have them point straight so they can be guided through the slots when the decoder board is installed.

Bend the tab on the right side in such a way that it avoids touching the frame. If necessary, wrap Kapton tape around the part of the frame where the tab might touch it.