Decoder Installation – Bachman Spectrum Dash 8 40C (HO scale)

Decoder installed – Digitrax DH123

Disclaimer: These are suggestions only – use at your own risk. I successfully used this series of steps to install decoders in one of these locomotives without damage to the unit. Take your time removing shells, it will save you time repairing or replacing parts in the long run. If you are not comfortable disassembling your expensive locomotive, please save yourself a lot of agony send it out to a reputable dealer.

Note: The section on installing the lights needs some cleanup. I need to find out the correct drill bit size to ream out the light holes, and the correct resistor size for the micro bulbs. I believe the bulbs are Miniatronics.

1) Disassemble unit.
1.1) Remove side frames from trucks.
1.2) Remove two bottom screws from fuel tank
1.3) Remove two screws securing frame to shell. Don't loose plastic keepers.
2) Remove circuit board from top of frame.
3) Disassemble frame halves. Watch drive train for pieces.
4) Motor
4.1) Remove black insulating tape from around motor.
4.2) Be careful not to loose brushes
4.3) Solder orange wire to top of motor
4.4) Solder gray wire to bottom of motor
4.5) Put electrical tape over solder points
4.6) Insulate motor from frame with electrical tape
5) Trucks
5.1) Remove universal joints
5.2) Cut off metal arches from each side
5.3) Solder red wires to the fireman's side of the front and rear trucks
5.4) Solder black wires to opposite side of trucks
5.5) Reassemble frame halves with modified trucks
6) Run wires through center crack in frame. There isn't clearance to run the wires
around the frame between the frame and the shell.
7) Use a piece of foam tape and make a mounting pad at the rear of the locomotive
frame.
8) Lights
8.1) Push out the front and rear lenses.
8.2) Pick up a light kit from (hobby shop) with the correct drill bit
(need to record size here in future)
8.3) Drill out light holes for 1.2mm 1.5 volt micro bulbs
8.4) Put lights in holes, secure with some white glue and let dry.
8.5) Solder common wires together from both front and rear sets of lights.
8.6) Put small heat shrink over leads for later
8.7) Solder (470?) ohm resistor to other lead of both lights (need to double check
resistor value)
8.8) Solder yellow wire to front lights (reverse of decoder instructions)
8.9) Solder white wire to rear lights (reverse of decoder instructions)
8.10) Solder blue wire to common leads
8.11) Use some electrical tape to route wires in the top of the shell
9) Put decoder on foam tape to mount
10) Cut leads to correct length. Leave enough to turn over shell when working on unit.
11) Connect motor and truck wires to corresponding decoder wires
12) Test unit on test track
13) Shrink heat shrink tubing
14) Replace shell, careful not to pinch wires.
15) Replace screws
16) Test unit final time.