Set your browser's left and right margins to 0.5" (File Page Setup) and print out this document. As each step in the installation is completed place a "X" or a check-mark through the bullet. All references to the frame are based on the front being at the top or away from you.
The cab/short hood is considered to be the front of the locomotive in the following descriptions.
A Digitrax DN93 decoder will be installed in the space underneath the fuel tank. Some frame modifications are necessary to accomplish this.
In normal analog (DC) operation, the U28C/U30CG picks up power from the right rail through the wires from the trucks to the circuit board in the fuel-tank area, which then connects to the bottom motor brush. Power from the left rail pickup is routed to the top motor brush via the frame.
Begin by testing the Digitrax DN93 decoder for proper operation per the instructions provided by Digitrax.
Remove the body shell and the fuel tank from the locomotive frame.
Remove the trucks from the frame by pushing out the retaining pins. Note that both trucks have wiper contacts against the wheels on the right hand side of the truck. This must be remembered when re-installing the trucks.
Pry out the printed circuit board from the fuel tank area with a small flat screwdriver or hobby knife. Unsolder the headlight wire from the printed circuit board. The printed circuit board is not used after the conversion, and can be discarded.
Using a magic marker or paint, place a mark on the motor at the top to ensure it will be replaced in correct alignment.
Remove the clips holding the motor, drive shafts and bearings to the frame, and remove the motor, drive shafts and bearings, laying out each carefully so it will be clear how they are re-assembled. Remove the headlight, headlight power contact and headlight wire, and set aside.
Using a motor tool with a ¼" metal cutting bit, enlarge the area beneath the printed circuit board to fully accommodate the decoder and wiring so that the fuel tank cover can be replaced on the frame at the conclusion of this installation. Be sure to preserve the cosmetics of the frame as viewed from outside the locomotive.
Smooth the edges of the cut area with fine sandpaper to ensure the insulation on the wires cannot be pierced.
Clean all of the grindings from the frame.
Remount the forward drive shaft and bearing in the frames using the two clips removed earlier. Replace the headlight, headlight power contact and wire, placing the wire in the channel along the right side of the frame.
Place a piece of electric tape on the underside of the top of the frame, just above where the top motor brush will be located when the motor is replaced in the frame. This will prevent any possibility of a short between the top motor brush and the frame.
Cut off the spring brush contact at the top of the motor at its base. Do not damage the portion attached to the motor, as it is the brush holder.
Cut the decoder green and yellow wires to ½". Twist the wires that were cut together, and wrap a small piece of insulating tape over the ends so they cannot short against the metal frame.
Cut the decoder orange wire to 1" and the gray wire to 1¾". Strip 1/8" insulation from each.
Pass the decoder orange and gray wires through the hole in the frame above where the printed circuit board used to be. Solder the orange decoder wire to the bottom brush holder of the motor, and the gray wire to the top brush holder of the motor. The gray decoder wire should be routed up the left side of the motor.
Note: solder the wires to the brush holders quickly, as too much heat applied during soldering may melt the plastic brush housing and permanently damage your motor.
Replace the motor in the frame, being careful to align the U-joint with the forward drive shaft, and secure with the clips removed earlier. Ensure the gray decoder wire is on the left side of the motor.
Using an ohmmeter, verify that there are no short circuits between the decoder orange and gray wires and the frame. Resolve any problems before continuing.
Connect the red and black decoder wires to a suitable power pack, and test for proper analog operation of the motor to ensure there is nothing binding within the frame. Resolve any problems before continuing.
For track power pickup, the red decoder wire will attach to the wiper on each truck, while the black decoder wire will connect to the frame.
Cut the wiper at the rear center of each truck to 1/16".
Cut the red decoder wire to ½", and strip 1/8" insulation from the end.
Cut the red wire previously cut from the decoder to a length of 1½", and strip 1/8" insulation from each end. Cut the remaining red wire previously cut from the decoder to ¾", and strip 1/8" insulation from each end.
When the decoder is fastened under the frame of the locomotive and covered by the fuel tank, the end with the wires will be oriented to the rear of the locomotive. Remembering that the electrical wipers inside each truck should be on the right side of the locomotive, place each truck beside the frame, properly oriented for later mounting in the frame.
Solder the 1½" red wire to the front truck wiper, then mount the truck in the frame and secure with the retaining pin.
Solder the ¾" red wire to the rear truck wiper, then mount the truck in the frame and secure with the retaining pin.
Bend the truck wipers as necessary to ensure they do not short to the frame during normal motion of the trucks when the locomotive is operating on the tracks.
Solder both red wires from the truck wipers to the decoder red wire, then insulate the joint. Make sure the wires to the truck wipers can flex as the trucks move.
Cut the white decoder wire to ½", and strip 1/16" insulation from the end. Strip 1/16" insulation from the end of the headlight wire. Join the two wires together and solder. Insulate the joint with electrical tape.
There is no place on the frame where the black decoder wire can be soldered, so it will be held in place against the frame by the fuel tank.
Dress all the decoder wires and the decoder into the space where the printed circuit board had originally been located, place the black decoder wire end against the frame just where the fuel tank fastens to the frame, and snap the fuel tank in place.
Test the locomotive for analog and digital operation on the layout. Resolve any problems and ensure the mechanism runs perfectly before continuing.
Note: if the locomotive runs in the wrong direction, the motor may be mounted in the frame upside down. Remove the brush retaining caps and turn the motor over. Replace the brush retaining caps and test again.
Replace the body shell on the chassis. The installation is now complete.
Test the operation of the locomotive on the railroad. It should operate just as if no modifications had been made. Resolve any problems.
Place the locomotive on the DCC programming track and set the DCC Command Station to the programming mode.
Program Configuration Variable "CV29" to "06" (for 2-digit addressing or "26" for decoders capable of 4-digit addressing) then program the decoder to the desired address.
Carry out a final check of the locomotive on the railroad.
Record the decoder CV's and address, and the reporting marks of the locomotive.
The conversion is complete. Enjoy your DCC-equipped locomotive.
