KB887: Digitrax Decoder Installation For PROTO 2000 E8/E9 in HO Scale

This article was last updated on April 18, 2012, 1:57 p.m. | Print Article | Leave Feedback

This installation procedure is for the DIGITRAX DH163/DH123 decoder. Alternatively, you can use a Digitrax DN142 in this installation. If you use the DN140 the installation will require fewer engine modifications because of the smaller physical size of the decoder.

Note any decoder of smaller physical size can be used in this installation.  DN135D, DN163, DZ123, DZ125, DZ143 are all possibilities.



After removing the shell from the locomotive chassis, note the color and location of each of the various wires.  All connections must be soldered with rosin core solder and insulated with shrink tubing.

We will locate the decoder in the forward part of the chassis behind the cab of the locomotive.

You will have to cut down the box immediately behind the "bulkhead" plastic piece so that the installed height of the decoder will not be higher that the weight.

We also suggest that the lower headlight bulb be replaced with a 12V bulb and relocated to bring the light in line with the lens in the door for more effective lighting and improvement of number board illumination.

1. Cut away enough of the bulkhead behind the crew to fit the decoder.

2. Relocate lower headlight bulb to be in line with the lens in the door and cement in place.

3. Connect the RED lead from the rear truck to the RED lead from the front truck together with the BLACK decoder lead.

4. Cut the two BLUE leads (from front and rear trucks) at the lighting board (center). Connect the Truck ends of these leads together with the RED decoder lead. The light board ends of the blue leads will NOT be used to make any other connections.

5. Coming out of the hole in the top of the weight are the three wires (1 black & 2 red) that connect to the motor . PLEASE NOTE: Some models use 1 YELLOW wire instead of Black and 2 BLUE wires instead of Red. If your unit is wired this way, remember to substitute wire colors in Steps 6 and 7.

6. Cut both RED wires that run from the motor to the light board (center) about 25 MM from where they exit from the motor; and again about 25 MM from the light board.

a. Connect the motor end of the 2 RED wires to the GRAY decoder lead.

b. Connect the light board end of the 2 RED wires to the GREEN decoder lead.

7. Cut the BLACK wire that runs from the motor to the light board (Fireman's side) about 25 MM from where it exits the motor cavity; and again about 25 MM from the light board.

a. Connect the motor end of the BLACK lead to the ORANGE decoder lead.

8. Cut the two white wires from the lighting board on the Fireman's side. These are for the lower, constant headlight control.

a. Connect the bulb end of either WHITE wire to the light board end of the BLACK wire; (Step 7) along with the BLUE decoder lead.

b. Connect the bulb end of the other WHITE wire to the White decoder lead. The light board ends of the WHITE leads will NOT be used to make any other connections.

*NOTE: If you are using the DN140 decoder you will connect the lower (constant) headlight using the WHITE and RED decoder wires as shown in the DN140 user manual.

*NOTE: If you have not replaced the 1.5V bulb with a 12V bulb, then you will need to install a 120 OHM 1/2 watt resistor in series with the one lead of the bulb. Tack the resistor to the underside of the sill.

Check all your connections, make sure they are solid and insulated. Before replacing the shell, place the locomotive on the track for a test drive. If your installation was done correctly, the lower headlight will be on constantly in forward motion, controlled by F0. The Mars Light can be turned on and off regardless of the direction by using the F1 function on your Digitrax throttle.

Before replacing the shell be sure that all wires are located side by side on top of the weight and secured with tape so that they take-up the least height, then replace the shell and you're ready to roll.

PLEASE NOTE THAT THE SINGLE RED, WHITE AND BLACK WIRES LOCATED ON THE ENGINEER'S SIDE OF THE LIGHT BOARD ARE NOT DISTURBED IN THIS INSTALLATION.

Technical note:
If using DH142, DN142, DN141K2, DN149K2 series decoder, when F1 is set up for FX, F2 must also be set up as FX (It can’t be used as standard on/off function.)  If you want to use a combination of FX & standard on/off functions, please use F1 as the standard on/off function and F2 as the FX function.

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