Decoder Buddy Information


This product is versatile in terms of direction of the placement of the board and mounting in various configurations.  It can easily replace a QSI board, a Dual Mode decoder board or be mounted directly on the electric motor or frame with Kapton tape.  (It is recommended that a piece of Kapton tape be placed on the bottom of the mother board to assure electrical isolation from the electric motor or frame.)

This mother board does not include the 21 Pin Decoder.

This mother board and connector board require soldering.

These printed circuit boards are NOT FOR USE IN A DC SYSTEM.

The on board resistors are sized for LEDs. (2.2K)

Now I have added Decoder Buddys with 0 ohm, 750 ohm and custom specified resistors for function outputs.  These may be requested by the email link.

The mother board includes; 

One 21 Pin Decoder receptacle,

Two pairs of track input pads,

One pair of motor input pads,

One pair of stay alive pads (U+ and GND),

{V5 pads for two Aux functions}

Two pairs of speaker pads wired in parallel,

Resistors for use with LED lighting. (on board 2.2K)  (Also available with 0 ohm, 750 ohm and custom specified resistors for function outputs.  this accommodates incandescent lamps or bulbs.)

The connector board contains pads for eight pairs {V5 contains 12 pairs}of lighting function connections. U+ or the blue wire has eight {V5 has twelve} connected pads for the common power source. The negative (-) discrete function pads are all labeled to indicate their connection to the functions available in the decoder.

If you require incandescent lamps there are procedures that require soldering and allow for incandescent lamp use or different Decoder Buddys made specifically the application.  Remember there are different incandescent lamp voltages and current draw that have to be taken into consideration also.

The lighting connector  was designed so that the shell of the diesel locomotive can be easily separated from the frame without unsoldering wires. This does require that the headlight and rear lights be mounted in the shell of the locomotive and that the diesel has a removable dynamic brake shell.

Decoder Buddy installed, speakers installed, decoder installed, and the motor is tested and ready.
Decoder Buddy installed, speakers installed, decoder installed, and the motor is tested and ready.

Original vs V5

Just a few thoughts on the original Decoder Buddy and the V5 Decoder Buddy.  I try to envision your thoughts from mine.  The original Decoder Buddy does all I wanted and still does.  It has 8 matched Aux outputs for lights on a detachable small connector board, pads for a stay alive and room to solder easily.  I would very tempted to use it in locomotives that didn't require any more than eight lighting functions.  The majority of decoders on the market at the moment have a maximum of eight  lighting outputs.  Having said that I have also considered uses for more than eight lighting outputs.  I have also considered ground lights which would be attached to the frame of the locomotive.  The V5 has 12 Aux outputs for lights.  Twelve are present on the small connector board and two are paired to the frame.  The track and speaker pads stayed the same size.  The pads on the small connector board got a little smaller.  These pads are all separated and have holes to help hold the wires.  The stay alive pads moved to the other side of the motherboard out from under the decoder and are in an easy place to solder to like the original.  From a little closer to the situation than I used to be, I might say a Steam / Diesel split might align with the two Decoder Buddys as well as a 1997 date split between the two due to ditch light requirements by the FRA.  Both are exactly the same size.  You get to make the choice!  Fortunately both Decoder Buddys have been accepted and are being used in models of the blue box era to the latest releases from all the major manufacturers.  Hope this helps your decision.....!


Decoder Buddy Size


Width x Length x Height

 O.67”  x  2.20”   x   0.35”

17 mm x 56 mm x 9 mm

Height may vary slightly 

depending on decoder.

Before and after in two of Jim Moe's Proto1000 RSC2s
Before and after in two of Jim Moe's Proto1000 RSC2s

Decoder Buddy Outputs for different manufacturer's decoder N

                  Original            V5 

Pin #       Decoder       Decoder     LokSound     LokSound     SoundTraxx    TCS     Digitrax**           

                   Buddy           Buddy              V4                      V5                  T2 & E2

  1                                         A10                                              A10

  2                                         A7                                                A7

  3                A6                   A6                     A6                     A6                                               F6*           F6

  4               A4                   A4                     A4                     A4                        Fx6              F4             F4

  5                                         A12                                              A12

  6                                        A11                                               A11

  7               F0r                 F0r                    F0r                   F0r                       F0r               F0r          F0r

  8               F0f                 F0f                   F0f                    F0f                       F0f               F0f         F0F

 13               A3                    A3                      A3                     A3                        Fx5                F3            F3

 14              A2                    A2                      A2                    A2                        Fx4               F2            F2

 15               A1                     A1                      A1                     A1                         Fx3                F1             F1

 17              A5                    A5                      A5                     A5                                                F5*           F5

* Note: TCS functions 5 and 6 are not programmable, and will only output constant bright lights.

** Unavailable for comment



An added benefit of Decoder Buddy beyond easy DCC decoder installation is YOU CHOOSE lighting functions.  Upgrade the motherboard that came with your locomotive for all the lighting functions available in your 21 pin decoder!  Ditch lights, blinking ditch lights, numberboard lights, step lights, ground lights, class lights, the list goes on.




9 lighting functions out of twelve available......

A little night operations......