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by Paul Norton

INTRODUCTION

Aristo-Craft, Plug and Play diesels are sold with a track power/battery power switch and MU plugs on each end. This project shows how to add the same switch and an MU plug to a USA Trains F-3A, so you can use either track power or a power car to run it. While this project deals with a specific locomotive, the principles are the same for other USA Trains, four axle diesels.

Three, 2-pin plug sets and a Double Pole Double Throw (DPDT), slide switch will be required for this project. The 2 pin-plug sets are available from All Electronics under catalog # CON-240, and the switch catalog # SSW-37.

REMOVING THE F-3B SHELL

Remove the two screws from the base of the coupler mounting brackets and remove the couplers. Put the screws back in the frame so they do not get lost.

Undo the two screws at the base of the fuel tank. Lift the fuel tank off and set it aside for now. Put the screws back in the frame.

There are nine screws holding the shell to the frame. These are hidden in deep burrows in the frame and will require a long Phillips #1 screwdriver to remove them. It is not necessary to remove the motor blocks in order to access these screws, however the first screw hidden under the front motor block is difficult to get at.

Gently spread the front of one of the side frames with one hand and push the motor block the other way with the other. Lift one the axle end out of it its bushing and set it on top of its journal. Repeat the process for the other end of the axle. The front of the motor block can swung up and the first screw removed. Replace the axle back in the side frames when done.

• The next two screws are under the side frames at the back of the front truck.
• Four are in the fuel tank area.
• The last two are under the side frames at the back of the rear truck.

Place a forefinger in the hole in the center of the frame and GENTLY pull down. The frame should bow SLIGHTLY. Push down on the front pilot anti-climber and the front of the shell should pop free of the frame. Pull the frame forward and the back of the shell should pop free. Lift the shell up, but just far enough to lay it beside the frame.

Identify the 2-pin and 3-pin connectors on the power distribution board for the front lights.

Unplug the connectors and set the shell aside.

INSTALLING THE ALL ELECTRONICS PLUGS

CAUTION: The 2-pin plug sets sold by All Electronics, hereafter referred to as AE plug sets, are not always colour coded the same as those in USA Trains locomotives. If the AE plug sets are not the same, just click on the following link to see how to switch the AE Plug wiring so that proper polarity is maintained.

Undo the twist ties that group the locomotive wiring together.

There should be two plugs from the front motor block, but only one plug has two red wires and two black wires attached to one side of it. This plug is for the front truck, track power pick-ups. It is attached to the power distribution board at PICK1. Undo this plug. Unplug an AE plug set. Plug half the AE set into the open plug on the power distribution board, and the other half into the open plug for the front truck, track power pick-ups.

There should be two plugs from the rear motor block, but only one plug has two red wires and two black wires attached to one side of it. This plug is for the rear truck, track power pick-ups. It is attached to the power distribution board at PICK2. Undo this plug. Unplug an AE plug set. Plug half the AE set into the open plug on the power distribution board, and the other half into the open plug for the rear truck, track power pick-ups.

Drill a 1/8 inch hole in the center of the frame, 5/8 of an inch from the back.

Cut a two inch length of shrink-wrap tubing and slip it over both the wires of the male portion of an AE plug. With the tab of the plug facing up, slip the wires through the hole in the bottom of the frame until the shrink-wrap is snug against the frame and plug. Apply hot glue over the wires on top of the frame for stress relief. This will now be referred to as the MU plug.

INSTALLING THE SWITCH

To be able to alternate between track power and battery power, a double pole, double throw (DPDT) switch must be installed.

The DPDT switch is mounted in an L shaped brass bracket on top of the rear weight. By mounting the switch here, there is no need to make a hole in the frame or shell. It is accessed through the rear door, allowing it to be thrown without lifting the locomotive.

This view shows the bracket held by the rear screw and washer for the weight. Two brass pegs, which fit into small holes drilled in the weight, keep the bracket straight.

WIRING THE DPDT SWITCH

Slip a length of shrink wrap over the red wire of the MU plug. Route the wire to the outside near the edge of the frame and then back to the DPDT switch so it does not interfere with opening the door. Solder the wire to the bottom right tab of the switch. Slide the shrink-wrap over the tab and heat gently to seal the solder joint. Repeat the process for the black wire of the MU plug, but solder it to the bottom left tab of the switch.

Note: Connecting opposing wire colours (red and black) allows identically wired motor blocks, which are mounted in opposite directions, to run in the same direction.

Gather the black wire of the AE plug attached to PICK1 on the power distribution board and the red wire of the AE plug attached to PICK2. Slip a length of shrink wrap over both wires. Solder them both to center right tab of the switch. Push the shrink-wrap over the tab and heat gently to seal the solder joint.

Gather the red wire of the AE plug attached to PICK1 on the power distribution board and the black wire of the AE plug attached to PICK2. Slip a length of shrink wrap over both wires. Solder them both to center left tab of the switch. Push the shrink-wrap over the tab and heat gently to seal the solder joint.

Gather the black wire of the AE plug attached to the front truck and the red wire of the AE plug attached to rear truck. Slip a length of shrink wrap over both wires. Solder them both to top right tab of the switch. Push the shrink-wrap over the tab and heat gently to seal the solder joint.

Gather the red wire of the AE plug attached to the front truck and the black wire of the AE plug attached to rear truck. Slip a length of shrink wrap over both wires. Solder them both to top left tab of the switch. Push the shrink-wrap over the tab and heat gently to seal the solder joint.

THAT’S IT! You have completed the installation of a track power/battery switch and an MU plug on your USA Trains F-3A. All that’s left to do is test to ensure the unit is wired correctly.

TESTING THE SWITCH and MU PLUG

Plug the lights back into the power distribution board, set the shell back on the frame and install the rear coupler. Ensure all wires are inside the mounting posts so they do not get pinched between shell and the lip of the frame.

Set the locomotive with a power car on a track powered railway. Flip the switch up to engage the track power pick-ups and test to ensure the motors and lights are operating properly. Now flip the switch down to engage the power car and test to ensure the motors and lights are operating properly.

Once the switch and MU have been tested, fasten the shell, fuel tank and front coupler to the frame.

CONGRATULATIONS! The switch and MU plug will allow you to run your F-3A locomotive with either track power or a trailing power car with all the benefits of battery power and radio control.