Happy New Year and welcome to another year of N Scale DCC decoder installs. During the past year DCC equipped engines have become the majority in my fleet. Maybe this year I can get to 100% DCC !
Starting with the 1997 release of their GP40-2, Atlas started producing N scale engines that could use a board type DCC decoder. The design involved having the bottom motor contact come around to the top and both the top and bottom contacts then touching pads on the bottom of the decoder board or the stock LED board. The idea being that the frame would not need to be modified and this was a great breakthrough for N scale DCC. This same design has been used on many models now and decoder boards to match this design are offered by all the major decoder manufacturers.
This design suffered from that connection between those contacts and the boards not being very reliable. For many years I had been wiring the connection between the motor and decoder. More recently with the wired decoders having gotten much smaller, I have found space between the stock LED boards and the frame and would connect the wired decoder into the LED board. I have posted several of these types of installations here on this blog including the GP40, SD35, and the SD50/60 series.
This photo shows how far I took the engine apart. The motor and gear assemblies are left in the right side frame throughout this installation.
Then replace the shoulder washers and press the left side frame on. Carefully guide it on over the decoder board, the shoulder washers, and the motor saddle.
After a successful test run of the engine mechanism, I normally solder the motor contact tabs to the decoder board. Then re-install the shell.
The principles of this installation apply to many other Atlas engines using these board type decoders.