October 2004

In the late 80's Kato introduced some
nice models of GP38-2 and the GP50. 

A DCC decoder can be installed in both
models using Trackmaster frames from
Aztec Mfg.  For this project I am using the
TM3013 frame to modify a GP50.  This
frame would also work for 2nd run of the
GP38-2 model.  The TM3011 frame would
be used for the 1st run of the GP38-2.

For this project I am using a Digitrax
DZ123 DCC decoder, but most of the
small wired decoders available today
would also work.

The first step after completely
disassembling the engine is to modify
the PC board.  This is a view of the board
from the upper side with the top being
toward the front of the engine.

   1.  Cut the board just behind the rear
        mounting screw holes.  The
        remaining board should be about
        1-7/8 inches long.

   2.  Remove the diode from the
        front end of the board.

   3.  Using the Aztec frame as a guide,
        cut a notch to match the slot on
        the left side of the frame.

 

After fully testing the decoder cut the
wires to the following lengths:

Red & Black = 7/8 inch
White & Gray = 1 - 7/8 inch
Orange = 2 - 3/8 inch
Yellow = 1 inch
Blue = 1/2 inch

Connect all the wires to the board
as shown in the photo to the right.
Use a Golden white LED for the
rear light with a 480 ohm resistor
in series with the blue wire then
place heat shrink over the
connections & the resistor.

 

To give extra protection against any
short circuits, place kapton tape on
both the upper and lower parts of the
frame, and on the inside of the
metal cover as shown in this photo,

Re-assemble the engine.

Run the orange wire down the left
side of the engine to the lower motor
brush.  The gray wire goes to the top
motor brush.  They both use the notch
on the left side of the engine.

Install the metal cover being careful
not to pinch any of the wires on the
guide tab at sticks up from the frame.
There will be enough room for the wires
between the frame and the metal cover.

Run the rear LED wires & resistor under
the decoder.  There should be room in
slot milled into that part of the frame.

After test running, secure the decoder with a small amount of scotch tape.  Be sure to trim it off clear
of the flywheel / worm gear.  Then re-install the fuel tank and shell.