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by Paul Norton

INTRODUCTION

Aristo-Craft, Plug and Play diesels are sold with MU plugs on each end. This project shows how to add the same plugs to a USA Trains GP38-2 so you can use a power car to run it. While this project deals with a specific locomotive, the principles should be the same for other USA Trains 4 axle diesels

NOTE: Nothing in this project prevents this locomotive from being restored to track power for re-sale at a later date. As the locomotive’s track power wiring will be unplugged during this project however, it will require a power car to run it. A power car is simply a battery car with a receiver added for on-board, radio control. To view an article on how to build a power car, just click on the following link.
Power Car

Four, 2-pin plug sets are required for this project. They are available from http://www.allelectronics.com under part number CON-240 for $1.35 each.

REMOVING THE TRACK SLIDERS

Remove the railings from the sides and ends of the locomotive to prevent possible damage and set them aside for now.

HINT: A small, flat screwdriver can be used to pry the railings from their holes in the frame. A Post-It Note placed between the locomotive and the screwdriver may prevent the paint from being scratched.

Place the locomotive upside down in a soft cradle. Remove the six screws (circled in red) from the bottom of each motor block and remove the bottom covers.

Remove the small chrome screw (circled in red) from each track slider bracket. Lift out the track sliders and the pieces of piano wire (indicated with yellow arrows) sprung between the axles.

NOTE: The track sliders and axle wipers are the only components removed during this project. They should be placed in a Ziploc bag, with the diesel model and road number marked on it, and taped in a pocket of the locomotive’s Styrofoam packaging.

Fasten the track slider brackets back in place with the small chrome screws. Fasten the covers back on the bottom of each motor block with their six screws.

HINT: Do not fully tighten any of the screws until all the screws have been inserted and turned down some. If you tighten the screws as you go, the last few may be hard to insert and may strip the threads in the plastic motor block.

REMOVING THE HOODS AND CAB

Remove the screws holding the coupler brackets and couplers to the frame. Set the couplers aside for now. Install the coupler bracket screws back in the frame.

Unplug the four wires from a motor block. Gently spread the side frame and slip one end of an axle from its bushing. Repeat for the other end. Repeat the process for the other axle and remove the motor block. Remove the excess black grease from the ends of the axles. Repeat the process for the other motor block. Set the motor blocks aside for now and wash the black grease from your hands.

Remove the two small screws (indicated by the yellow arrows) from the base of the fuel tank. Remove the fuel tank and set aside for now. Install the fuel tank screws back in the frame so they don’t get lost.

Remove the twelve long screws holding the hoods and cab to the frame. These are hidden in twelve deep holes. Four (circled in yellow) are inside the side frames under the long hood.

Four (circled in yellow) are under the fuel tank.

The last four (circled in yellow) are inside the side frames under the cab.

Lastly remove the four short screws (indicated by the yellow arrows) that hold the battery boxes to the frame. Their heads are not recessed.

Turn the locomotive over. Carefully lift the shell from the front of the long hood. The whole shell (long hood, cab, battery boxes and short hood) will lift off as one piece.

CAUTION: Do not lift the shell off too far or the wiring may unplug.

Install the four screws back in the battery boxes and the twelve screws back in the long and short hoods.

INSTALLING THE MU PLUGS

CAUTION: The two pin plugs sold by All Electronics are not always colour coded the same as the plugs in USA Trains or Aristo-Craft diesels. If the plugs are not the same, just click on the following link to see how to change the wires so that proper polarity can be maintained.
MU Plug Wiring

There should be two plugs for the motor block under the long hood, but only one plug (indicated with the yellow arrow) has two red wires and two black wires attached to one side of it. This plug is for the track power pick-ups, the other is for the motor.

Undo the track power plug. This isolates the track power pick-ups and prevents battery power from being feed back into the tracks.

There should be two plugs for the motor block under the cab, but only one plug has two red wires and two black wires attached to one side of it. Unplug it.

Drill a 1/8 inch hole (indicated by the blue arrow) in the center of a pilot between the coupler cut-bar and the grab rail.

The hole (indicated by the yellow arrow) should pass through the pilot and both sides of the box on the frame in front of the coupler return spring.

As only the male halves (indicated with red arrows) of the four All Electronics plug sets are needed for this project, unplug the females halves and set them aside. They can be used later for power cars and other projects. Hereafter the male halves of the sets will be referred to as the AE plug.

Flip the chassis over and drill a 1/8 inch hole in the frame opposite the screw holding the coupler return spring. Slide a 3/4 inch length of shrink wrap over the wires of an AE plug until it reaches the back of the plug. With the tab of the plug facing up, feed the wires over the coupler cut bar, through the holes in the pilot, the box on the frame and the frame.

The shrink wrap will provide the proper spacing for the plug and the coupler cut bar will prevent it from falling on the coupler. Repeat the process for the other pilot.

Insert another AE plug into the plug (indicated with a yellow arrow) on the power distribution board of the diesel.

Gather the ends of the wires of this AE plug and the AE plug installed on the long hood pilot. Trim the wires to length and strip 1/4 inch of insulation off all four wires. Slip a 3/4 inch length of shrink wrap over one of the red wires, and over one of the black wires. Solder the red wires together. Slip the shrink wrap down over the joint and warm until it seals. Repeat for the black wire.

Insert the last AE plug into the plug indicated with a yellow arrow.

Gather the ends of the wires of this AE plug and the ends of the wires of the AE plug installed on the short hood pilot. Trim the wires to length and strip 1/4 inch of insulation off all four wires. Slip a 3/4 inch piece of shrink wrap over one of the red wires, and over one of the black wires. Solder the red wires together. Slip the shrink wrap down over the joint and warm until it seals. Repeat for the black wire.

THAT’S IT! You have completed the installation of MU plugs on your USA Trains GP38-2. All that’s left to do is test to ensure the unit is wired correctly before re-installing the shell.

TESTING THE MU PLUGS

Grease the ends of the axles and place the motor blocks back in their side frames one axle at a time. Slip the four wiring connectors back on their pins of each motor block. The outside wires are the unplugged track power wires soldered to the side frames. The next two are the motor wires. The two in the center are unplugged track power wires from the sliders and axle wipers which were removed earlier.

NOTE: The colour coding of the wires alternates across each motor block.

Plug a power car into either of the MU plugs. If a power car is not available, connect the female portion of an All Electronics plug set to a small power pack for testing. Test to ensure the headlights and motors are both operating in the proper direction.

Repeat the test for the plug on the other end of the locomotive.

If the headlights and motors are not in synch, check the colour coding of the wires of the four AE plugs to ensure they line up with the USA Trains plugs.

ASSEMBLING THE LOCOMOTIVE

Once the power plugs have been tested; the shell, fuel tank and couplers can be replaced. Remove the four screws from the battery boxes and the twelve longer screws from the shell.

CAUTION: When installing the shell to the frame, all wires should be inside the mounting posts so they do not get pinched between shell and the lip of the frame.

Place the locomotive upside down in a soft cradle and install the four short screws in the holes (indicated with the yellow arrows) that hold the battery boxes to the frame. Install four longer screws in the holes (circled with yellow) between the side frames under the cab.

Install four screws in the holes (circled in yellow) under the fuel tank.

Install four screws in the holes (circled in yellow) between the side frames under the long hood.

Remove the two small screws from the frame and re-install the fuel tank with them.

Remove the two screws from each end of the frame and re-install the coupler brackets and couplers.

Install the railings on the sides and ends of the locomotive.

CONGRATULATIONS! These new plugs will allow you to run your GP38-2 locomotive with a power car and enjoy all the benefits of battery power and radio control.