Tap Creek

The Chicago & North Western Tap Creek Branch


Step 1

Gently remove the shell and the trucks. The picture below shows the frame after this step. The arrow points where we intend to put the decoder.

Step 2

The next step is to prepare the decoder. The picture below shows the decoder as delivered.

Generally there is space enough for the decoder as is, but it is essential that there is enough room between the decoder and the rear end of the shell. If part of the decoder, or any wires, occupy this space the shell will not seat properly, and the rear coupler will most likely not function as it should. This since it will end up at the wrong height above the rails.

To avoid this problem remove part of the decoder’s plastic insulation “wrapper”. This makes the decoder shorter, and it can thus be stuffed further in, below the light board. Do also remove part of the insulation above the wires. This makes it possible to later thread the wires close to the light board, once again creating more room just to the rear of the decoder. The picture below shows how parts of the insulation have been removed. Use a sharp knife to remove the plastic, but go gently so that you do not damage any wires or the decoder it self.

Step 3

Now, let’s turn our attention to the light board. Separate the frame halves so that you can remove the light board. This Printed Circuit (PC) board logically has three functions, as indicated in the picture below. The picture shows the down side of the board.

1. The front LED and its associated electronics

2. The motor contact pads

3. The rear LED and its associated electronics.

Also visible in the picture are the four pads that make electrical contact to the frame (The bare metal in the “inside” corners). There are two pads on each side of the board, both making contact with the same frame half.

The picture below shows the up side of the board.

Originally, all parts of the board make direct electrical contact with the shell and each other. The electronic components make sure only the LED in the current direction of travel is lit.

Step 4

When we convert to DCC we want the different parts of the light board, and the motor, to be controlled by the decoder. Our next step is then to electrically separate the different parts of the board. We do that by cutting the conductors on the board in some selected spots. On the down side of the board do the following.

1. Using a razor saw or a jeweller’s file, cut the conductor at the spots indicated by a red line in the picture below. Do only cut the conductor on the indicated side of the board. Do not cut through the complete board. If you have an Ohm-meter, use it to check your cuts.

2. At the spots indicated by a blue circle, remove the thin insulation to reveal the metal conductor beneath. These are the spots were we will later connect the decoder wires.

Do the same on the top side of the board, in the spots indicated in the picture below.

Now the different parts of the board have been electrically separated from each other.

Step 5

We might solder the decoder wires directly to the contact spots we created in the previous step. But if we do, most wires will run under the light board. I find it more convenient to have them running on the top side. This makes it possible solder (and un-solder) the wires with the light board in place in the frame and the frame completely assembled. This is kind of handy.

To make it possible to have the wires on the top side, the next step is to drill holes in the light board (In the next step we will thread and solder contact wires through these holes). Drill holes at the indicated positions, close to the contact spots we created in the previous step. Do also drill holes close to the original motor contact pads. Make sure all holes are clear of any conductor or component on the reverse side of the board.

The width of the holes is not critical, as long as the wire you intend to use gets through. I used a #70 drill bit and .010” diameter wire.

The description continues on the next page...

DZ143 Decoder in GP30

This decoder installation is easy, in the sense that it does not require any modification to the locomotive frame – no filing, no milling. But on the other hand some basic soldering knowledge is required. It is also assumed that you know how to disassemble and later re-assemble an N scale locomotive. I installed a wired decoder, and not a plug-n-play decoder, for the simple reason that at this time there was no such decoder that fit the Atlas GP30 (2006 version)

The approach is as follows:

· Reuse the original light board, including the front and rear LED:s.

· Cut the connectors on the original light board in some strategic places.

· Connect all decoder wires to the light board

· Place the decoder in the rear end of the locomotive, under the light board


The pictures on this page show how I installed a Digitrax DZ143 decoder, but the same principle ought to work for any brand of decoder, small enough to fit.

Decoder Installation (DCC)
Digitrax DZ143 in an N scale Atlas GP30