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 NSN RRR comes with two Drive Shaft Extension castings that replace the normal drive shafts, plus a small piece of 0.40" x 0.80" styrene which will be glued inside the shell at the rear to maintain alignment of the shell in the decoder area.
In normal analog (DC) operation, the right half of the frame connects to the right rail and the bottom motor brush, and the left half of the frame connects to the left rail and the top motor brush.
Begin by testing the Digitrax DN93 decoder for proper operation per the instructions provided by Digitrax.
Remove the GP9 shell, by prying out on the bottom of the cab carefully with a hobby knife (both sides) until the cab is freed, being very careful to pull the handrails out from their holes in the cab. Then remove the hood casting and, finally, the handrails and walkways. Place aside where they will not get damaged. They are not used again until the final step.
Remove the shroud around the front lamp by sliding it towards the front of the frame.
Remove both the front and rear lamp boards by pulling the front board towards the front and the rear board towards the rear of the frame.
Prepare the RRR by removing any flash found upon the casting using files and a hobby knife with No. 11 blade. Do this very carefully with reference to the Atlas frame, to ensure no mounting tabs or other needed metal are removed. Note and mark the right half of the Retroframe by comparison with the Atlas frame.
If you bend the frame a bit during the filing and fitting procedure, place the interior surface of the frame on a known flat surface. Place a piece of scrap wood on the exterior surface and tap it firmly with a hobby hammer.
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Place the mechanism on its side, screw head side up, and remove the screws. Once the screws are completely loose, hold the frame up and press down on the screws so the nut on the other side will pop out. Using a flat blade screwdriver, gently pry the two halves of the Atlas frame apart, carefully lining up parts on your work surface in the same order as they are removed and noting what each piece is by looking at the diagram Atlas provided with the locomotive.
If the two halves of the frame do not come apart easily then locate the four holes around the motor in the center. This is where the motor saddle locks the two halves together. Gently lift and push the tabs to release the saddle clips.
Before removing the motor, make note of which motor brush contacts the right side of the frame, and place a mark on the motor (piece of tape; dab of paint, etc.) to indicate the top. Note that some Kato motors are already marked with a white stripe, either on top or on one side near the top.
Check to find if the shaft bearing blocks fit the RRR as they should, and remove material from the RRR to permit that to happen, if necessary.
If your are going to modify the Atlas frame yourself, do so now following the instructions in the section above.
Before installing the decoder, re-assemble the mechanism using the Redi-Retroframe in place of the OEM frame.
To cut the drive shaft extension castings to the correct length, place the motor in the frame, and the shaft bearing blocks and worm gears in the RRR. The plastic casting with four legs on the end of each worm gear assembly should face the motor. Place the Drive Shaft Extension casting in one of the slots, then mark at the same place on the slot at the other end. Cut the Drive Shaft Extension casting to fit; note that there should be a little "play" and not be tight.
Install the trucks, etc. - everything except the body parts. Put the assembly on a test track and make sure the locomotive runs as it should, checking both directions, etc. When operating correctly, disassemble it again as described above.
Pry the brush holder caps up from the motor housing and remove the contact strips. Replace the brush holder caps.
Place the motor back into its normal location in the left half of the retroframe. Hold the decoder in its mounting location on the top rear of the frame, and mark off the length of the gray wire needed to reach to the top motor brush, then add ¼" and cut the wire. Similarly, measure the length of the orange wire needed to reach the bottom motor brush following the wiring channel in the frame, add ¼" and cut the wire.
Strip 1/16" insulation from each of the orange and gray wires.
Solder the orange wire to the bottom brush retaining cap on the motor, and the gray wire to the top retaining cap. The soldering of the wires to the brush holders must be compact to ensure enough spacing to be free of both frame halves.
Note: always remove the motor brush caps before soldering to them. Then lightly sand them to get a good clean surface, and apply liquid flux. Finally, solder the wires to the brush cap.
Do not attempt to solder to the motor brush caps while they are still in place in the motor, as too much heat applied to the brush caps during such soldering may melt the plastic brush housing and permanently damage your motor.
After soldering the wires carefully replace the brush, spring and brush cap into the motor.
Carefully place insulating tape over the brush retaining caps to ensure they cannot short against the frame.
With the left mainframe laid out in front of you (short hood to your right), install the motor with the orange wire on the bottom and the gray wire on the top. Route the orange wire to the top of the frame in the wiring channel provided in the frame. Inspect the brush holders and wires to be sure they are not touching the frame.
Install the front and rear worm assemblies, insulating bushing and drive shaft extension castings in the frame.
Position the green motor spacers so the nubs line vertically against the frame, i.e. top and bottom of the frame. Ensure they are placed in the little channels on the frame. This step is very important to smooth mechanical operation of the mechanism.
Install the front and rear insulating bushings in the frame.
Place the right mainframe on to the left mainframe, being careful that the orange and gray wires remain in the wiring channels. Install the front and rear nuts and screws, but do not fasten too tight.
Using an ohmmeter, check for shorts between each motor brush and the frame, and between each half of the frame. Correct any problems before proceeding.
Connect the red and black wires of the decoder to a suitable power pack, and test for proper analog operation of the motor to ensure there is nothing binding within the Retroframe. Resolve any problems before continuing.
The red and black wires connect to the frame via the screw and nut at the rear of the frame. Holding the decoder in its place on top of the frame, determine the length of the red and black wires needed to reach the nut and screw, then add ¼" and cut each wire. Strip 1/8" insulation from each wire.
Remove the screw and nut from the rear of the frame, holding the frame together with your fingers or a small C-clamp (be careful not to over tighten or you will bend the frame).
Place the stripped part of the red wire under the nut as the nut is pushed into the right half of the frame. Be careful that the wire does not go into the hole through the frame.
Place the stripped part of the black wire under the screw as the screw is pushed into the left half of the frame. Be careful that the wire does not go into the hole through the frame.
Tighten the screw until the frame is secure.
Using an ohmmeter, check for a short circuit between the two halves of the frame. If a short is detected, it is probable that the red and black wires are shorting through the frame screw/nut hole. Undo the screw and nut, and reposition the wires carefully. Tighten the screw and nut, and test again.
Loosen the screws enough to install the trucks, then fully tighten the frame. Make one more check for a frame short with an ohmmeter. Resolve any problems.
Cut the decoder green wire to ½". It is not used.
Ensure the white and yellow wires cannot short against anything or each other, and test the locomotive for both 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 locomotive upside down. Remove the brush retaining caps and turn the motor over. Replace the brush retaining caps and test again.
Carefully cut the left hand trace on the front headlight assembly circuit board just in front of where it meets the RRR, as shown below, so the circuit is not complete to the left half of the RRR.
Mount the front headlight assembly to the RRR in the normal manner.
Solder the end of the white wire to the left trace on the lamp circuit board in front of the cut made previously.
Snap the front lamp shroud back in place.
There is not sufficient clearance over the decoder to use the rear headlight assembly directly. The circuit board must be removed.
Note: the diagram shows an alternate way of connecting the decoder read and black wires to the frame.
Carefully unsolder the LED and resistor from the circuit board, and solder the resistor directly to the same wire from the LED that it was soldered to on the circuit board; this is important for polarity reasons.
Solder a wire from the resistor to the part of the left trace on the forward light circuit board that contacts the frame, i.e. the part of the trace opposite where the white wire is soldered. Solder the yellow wire from the decoder to the remaining terminal on the LED. The final wiring diagram is shown above.
Test the locomotive to ensure proper operation of all functions of the decoder. Resolve any problems.
Position the decoder and rear light in place over the RRR, and, using electrical tape, tape in place. Dress all wires over the top of the frame and to the rear of the frame so they will not interfere with the body as it is placed back on the frame. Adjust and secure with tape as necessary.
Cut a piece of the 0.40" x 0.80" styrene that is glued, on the 0.80" side, to one side of the frame at the decoder end to insure that the shell will be in alignment end-to-end, as the relocation of the frame's nut/screw/spacer is now closer to the motor. The styrene now performs the shell alignment function.
Place the handrails and walkways on the frame, then replace the hood. Check to ensure all wires are positioned out of the way, and that they do not cause the hood to bow out anywhere. Replace the cab, and put the handrails in their proper holes in the cab. Installation is 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.
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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.
Note: The portion of the retroframe which shows beneath the locomotive, such as the fuel tank, is bare metal and should be painted to match the paint scheme of the locomotive. Use the color of the Atlas frame as a guide.
