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Decoder Installation into a

Stewart F-3

by John V. Baum    J V 

1.  Remove the shell from the locomotive. 

2.  Refer to the attached diagram.  Unclip the front truck leads from the annealed copper wires on the wiring board.  Gently slip the copper wires from under the plastic retainer clips on the front half of the wiring board. Freeing the copper wires will free the wire leads from the headlight as well. 

3.  Slip a section of fine head shrink tubing over each copper wire and slide it to the rear of the locomotive until each section is directly over the copper strips which lead to the motor brushes.  Insulated electrical tape may be used for the same purpose.  The idea is to eliminate any possibility of electrical contact between the motor and the truck leads. 

4.  Reposition the annealed copper wires under the retainer clips, and clip the front truck leads back on the wires.  Do not reposition the headlight leads under the copper wires.   Attach the decoder to the wiring board with double-sided foam tape. 

5.   Refer to the diagram.  Solder the orange and gray wires from the decoder to the copper strips which lead to the motor brushes.  Solder the red and black wires from the decoder to the annealed copper wires.  Eliminate the possibility of a short by running a continuity check between each wheel on the locomotive and each brush.  If your meter shows continuity, you must isolate the short before applying power to the decoder!

6.  The leads on the factory supplied headlamp are not insulated.  Replace the factory supplied lamp with a lamp of your choosing, and connect the white and blue leads from the decoder to those leads.   Heat shrink tubing should be slipped over the decoder leads prior to making those connections, and positioned over the connections once they have been completed to prevent shorting.   If you replace the factory supplied headlamp with other than a 12 volt bulb, you will need to wire an approriate resistor in series with the bulb. 

7. Digitrax recommends 680 ohm resistors for LED's, 560 ohm resistors for 1.5 volt grain of rice bulbs, and 250 ohm resistors for 1.5 volt grain of wheat bulbs.   You may need to either increase or reduce resistor values from those which are recommended. 

8. Re-assemble the locomotive.

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