Athearn SD40-2 Snoot:
T1 Decoder Installation

First remove the couplers and lift off the shell.

Next remove the metal bar which connects the trucks.

Now remove the copper bar from the top of the motor.

Next slowly rock the motor back and forth until it comes out.

Remove the bar from the bottom of the motor, clip off the fingers which contacted the frame, solder the orange wire to the underside of the copper bar and attach it to the top of the motor as shown below.

Next kapton tape over both the underside of the steel bar, and the top side of the copper bar, as shown below, to prevent a short.

Now attach the gray wire to the bar from the top of the motor, and attach the bar to the bottom of the motor, as shown below. You can now reattach the motor to the frame.

Now reattach the steel bar to the top of the motor and solder the red track pickup wire to it as shown below.

Next, to connect the black wire to the frame, we drilled and tapped the frame to insert a screw and washer for the black wire as demonstrated below.

Now attach two wires to the blue wire coming off the decoder.

We are going to use a surface mount LED to light the reverse light, and a 3mm through hole LED to light the forward light. Follow the steps below to connect the lights. In the next section we will use a 2-Pin Connector (for ease of installation), a Golden White surface mount LED, and a Gold White 3mm LED.

For the rear light attach the yellow wire to the white lead on the 2 pin connector, and one of the blue wires, to the black lead on the two pin connector. Tape the two pin connector to the steel bar as shown below.

Attach the opposing side of the 2 pin connector to a 680 ohm 1/4 watt resistor and to the surface mount LED on the inside of the shell as shown.

For the forward light attach the anode of a 3mm LED to a 680 ohm 1/4 watt resistor to the remaining blue wire. Then the white wire to the cathode of the LED. Mount it in the light housing as show below. Wrap the outside of the LED in electrical tape to avoid lighting up the cab.

Finally, tape the decoder atop the steel bar and make sure the wires will not come in contact with the flywheel.

Reattach the shell and you are ready to run your locomotive.