DZ123 in a Kato GP38 or GP50

This material first appeared on my old web site in 2004.

In the late 80's Kato introduced some nice models of the GP38-2 and the GP50 that were built on very similar mechanisms.  These mechanisms were an improvement over what had been available up to that time and another stepping stone to get to what is available today.  It is possible to install a decoder in these older engines and here's how to do it.

The locomotive must be completely disassembled and the frame milled to make room for the decoder.  I sent mine to Aztec Mfg. for milling.






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.

This installation uses the original PC light board. This photo shows the modifications I made to the board.  Cut the board just behind the rear mounting screw holes.  The remaining board should be about 1-7/8 inches long.

Remove the diode from the front end of the board.  Using the Aztec frame as a guide, file a notch to match the slot on the left side of the frame.








On this particular installation I had used the Digitrax DZ123 decoder.  Digitrax has replaced the DZ123 with the DZ125.  Other decoders that would work include the TCS M1 or Z2, The Zimo MX621, or Lenz Silver Mini.

This photo shows the decoder wired to the board and the motor brush caps installed on the orange and gray wires.  The lengths of the wires are as follows:

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




In this example I used the original light front light bulb and connected the white wire directly.  If an LED is used then put a 480 ohm resistor between the LED and the white wire.  Do the same for the rear LED using the blue wire for the return path.

To give extra protection against any possibility of 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.

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.