Basic Installation

Tools required;

Soldering iron 15 Watt range,

Solder and flux,

Cutting pliers and pliers,

#1 Phillips screw driver, 

(#2 Phillips screw driver to remove the weights from the frame)

Wire stripper,



Checklist Procedure;

Remove the shell of the locomotive,

Desolder or cut wires from printed circuit board

     Track wires (2 or more),

     Speaker wires (2),

     Motor wires (2),

     Light wires,

     Stay alive wires (2) it is important to label (or measure) polarity,

Remove printed circuit board  

Attach the Decoder Buddy motherboard to the chassis, frame weights or motor.


     Track wires (2 or more),

     Speaker wires (2),

     Motor wires (2), (test the direction of the motor before soldering),

     Stay alive wires (2) to the correct polarity terminals (U+ and GND) if desired,

     LED light wires to the connector board,

Attach the connector board to the motherboard.

Test the installation before firmly attaching the shell.

Enjoy your newly updated locomotive!!!



Additional Motherboard Information


The mother board and the connector board are easier to see in this expanded view (below).

On the motherboard the four pads arranged vertically on each end are, from top to bottom, Track, Speaker, Speaker, Track.  The Speaker pads are wired in parallel, top to top and bottom to bottom.  The four labeled pads across the top are U+ {a nominal 14 volts and the place where the stay alive blue (+) wire is attached,} GND is ground for the stay alive and two MOTOR connections (Orange on the left and Gray on the right).  The two motor pads have through holes in the center to allow for wire insertion from the bottom of the printed circuit board for a neater connection.  A consistent motor connection color scheme does not seem to exist so these two pads are not labeled as to polarity or color.  You should test that the locomotive runs in the correct direction before reinstalling the shell.  U+ and GND are provided for a stay alive.  The NMRA Standards state that the positive pin (U+) of the 21 pin decoder should be connected to the blue wire (+) of the capacitor (stay alive).  The 21 pin connectors should fit into the decoder easily.  Do not try to force either connector board or decoder onto the pinned headers on the motherboard until pins are correctly positioned. After the pins are aligned properly firmly press the connector board or the decoder onto the motherboard so there is no space between the header and the printed circuit board.  If disassembly is required a sharp or narrow object inserted at the end of the connector to move the board a little at a time from each end is effective.



Additional Connector Board Information


The connector board is arranged so the wires from one end of the locomotive are routed though one side of the locomotive and wires from the opposite end are routed through the other side.   Function 0f is usually the front headlight and function 0r is usually the rear headlight.   A1, A3 and A5 occupy the pads on one side of the connector board.  This was done in an attempt to organize the decoder functions and output wires to the front and back of the locomotive. (See the compatibility table for different decoder manufacturer’s pin configuration outputs.)  U+, the blue wire or common are all connected to the four holed pads which are both connected within the connector board.  Note that when the direction of the <=DECODER points toward the 21 pin decoder the keyed 10 pin connector will mate properly.  The connector board and the pinned header on the motherboard should fit together easily.  Do not try to force either connector board or decoder onto the headers on the motherboard until pins correctly positioned. After the pins are aligned properly firmly press the connector board or the decoder onto the motherboard so there is no space between the header and the printed circuit board.  In some installations it may be possible to separate the connector board from the motherboard before removing the locomotive shell.  This makes the process of separating the frame and motor parts from the lights in the shell less cumbersome.  

Common Issue


Decoder seems loose fitting.

If the decoder seems to be loose fitting or has poor contact it is probably not seated onto the connector on the Decoder Buddy motherboard.  The picture at the left shows a decoder that is not seated.  The decoder printed circuit board should be pressed tightly to the plastic connector of the Decoder Buddy.  The same is true of the small square lighting connector board.  It must be pressed tight to the connector on the motherboard.

removing Connector boards and Decoders from the motherboard

Take your time.   The bent pliers method also works well on your 21-pin decoder1

Connector Board and Decoder Removal

There are three ways to deal with the situation if you wish to do so.  The three procedures all start with “as carefully as possible.... ”  Then proceed with either use; a screw driver to work the pin connector from one side then the other, a curved pair of needle nose pliers to pry near the plastic part of the connector or with the fingernails of your thumb and middle finger on the  diagonal corners pull the Connector Board.   I prefer using tools only as opposed to my fingernails for decoder boards because I have more control with tools.  It seems like I am very likely to bend pin 12 if I only rock a decoder with my fingers or fingernails.    Generally  the  decoders  and  connector  boards   come  out  unscathed.    It’s the pins in the two connectors on the  motherboard that are the liable parts.

Take  your time.   The curved pliers method works best for me on the  connector  side  of  the  21-pin decoders.  Rock it from end to end.

If you happen to bend a pin, carefully straighten it with a pair of needle nose pliers of an appropriate size.

Good How To Solder Video

Great soldering video from Julian Ilett, a guy I watch regularly and respect.  I use my brass shavings differenty.   I poke and rotate firmly when my tip gets that black and dirty.  When it is clean and shiny I re-tin it and either clean off the excess solder and continue or put it back in the holder then clean the excess solder off when it’s time to use it again.

A Good Soldering Tip Cleaning Tip Video

Paul is another of my favorites.  Check out this video on cleaning and care of soldering iron tips.

(I withheld the puns with physical restraint!!!)

Why 6 millivolts?

Check out this great video about  LEDs