This installation documentation is for the N-Scale Walthers EMD SW9/1200. This installation uses the MT1500 decoder and was performed by TCS.
Also used in this installation is TCS 30AWG wire for making the motor connections.
Shown here is the Walthers EMD SW9/1200 prior to installation.
To start off this installation, remove the fuel tank by pulling straight downward. After the fuel tank has been removed, remove the trucks by rotating them and pulling downward.
Once the trucks and fuel tank have been removed, the walkway piece can be taken off. To do this, use a small flat-head screwdriver and pop all four corners loose. Once loose, the walkway will pull straight off the bottom of the chassis.
Flip the model onto its roof. At the front of the hood on the bottom side you will see a notch on either side of the frame. Using a small flat-head screwdriver, leverage these points to loosen the shell from the frame.
Similarly, at the rear of the hood near the cab on the bottom side you will see a notch on either side of the frame. Using a small flat-head screwdriver, leverage these points to loosen the shell from the frame. With all four of these points loose, you can remove the shell from the frame by lifting up on the shell and pulling down on the frame.
Shown here is the frame with the shell removed and the original DC light board installed.
Remove the DC light board from the frame.
This DC model features motor contacts which directly mate with the frame. In order to convert to DCC, there must be complete isolation of track and motor power. This means we must remove the motor and isolate it. To start this process, use a small flat-head screwdriver to gebtly part the frame halves as shown.
With the frame gently spread apart, the motor and plastic retainer can be pulled upward and out as shown here.
Next, remove the motor from the plastic retainer by gently pulling on each side of the plastic retainer. The motor can be lifted free. We chose to mark the orientation of the motor with a marker as it was removed so that it could be re-installed in the correct orientation and polarity. It is important the the parts line up as shown above when re-assembling. Note also that the flywheel on the motor will face toward the cab.
On the top and bottom of the motor are copper-brass clips which made contact with the frame. Remove these clips. They may be clipped and soldered to, but we chose to solder directly to the terminals on the motor. The TOP of the motor in our case was the POSITIVE side of the motor. Onto this contact, connect your ORANGE wire. We will be using TCS 30AWG wire for this installation. The diameter of this wire is a perfect fit for the pins on the MT1500 once they have been tinned!
Once you have soldered your new wires onto the motor, it can be re-installed into the retainer and then the frame. Make sure you do not crush or crimp your wires! Any exposed copper or damaged installation can lead to a short and potentially damage the decoder!
We highly recommend installing a small piece of Kapton tape to the front of the frame as shown to prevent shorts of the decoder to the frame. Ensure the tape does not make contact with the worm gear or you could damage the motor or the decoder - not to mention your model would begin running terribly! Cut your tape to cover ONLY the top of the frame in the area shown.
With Kapton tape in pace, the decoder may now be installed by simply sliding it into place. On our model, we noticed that the fit was slightly loose. As a result, we applied a VERY THIN covering of solder to the pads on the top of the decoder to make up the rest of the gap. Precision solder is highly recommended.
Now that the decoder is in place, we can trim and tin our wires. We cut the wires to match the length of the chassis. After they were cut, approximately 1/8 inch (3mm) of insulation was stripped and the wire tinned generously. Once trimmed, stripped, and tinned, the wire may be inserted into the pins of the decoder as shown. Note that the ORANGE wire is the POSITIVE and will operate the unit long-hood-forward using this orientation. If you would prefer to operate in the opposite direction, simply reverse these wires.
To finish your installation, reverse the disassembly steps above; however, we found that it is easier to install the walkway piece first by pulling it down over the top of the frame, rather than from the bottom up. Your N-Scale Walthers EMD SW9/1200 is now TCS DCC-equipped and ready-to-roll!
Important Soldering Tip
Please do not use any flux either liquid or paste on the mother board. Over time, the acidic properties of liquid or paste flux will begin eating away at the fiberglass PCB and will damage it. Use only Rosin-core solder or no-clean flux approved for electronics use.
TCS recommends the use of Kester "44" Sn63 Pb37, .015" diameter Rosin-core solder. Kester part number 24-6337-0007.
You can order this solder from the following retailers:
Digikey - PN:KE1110-ND
Techni-Tool - PN:488SO6775
Other solder tips
When stripping wire, only strip a tiny little bit of the insulation. Strip no more than a 1/32 of an inch. When the wire gets tinned with solder, the insulation will shrink back more. Try to not expose any more wire than half the length of the solder pad at most. In no case should solder or exposed wire wire ever be outside the boundary of the the solder pad you are attaching a wire to.
Click here for important information on properly Stripping and Tinning wire