TCS K2D4 decoder N scale Kato RSC-2 Ron Bearden The K2D4 is a fairly easy install decoder for the Kato RSC-2. It's designed to be a drop fit for this loco. What makes it a just a little bit tricky is not so much the decoder as the loco. The loco is really small. This same decoder is designed for the mammoth SD80, but it is just barely squeezed into this RSC-2. First pull off the shell. It comes right off. Grasp by the walkway and carefully lift the walkway, body shell and cab. Sometimes you might need to remove the fuel tank and hold on to the metal to have something to pull against. Here is the bare chassis. The stock light board can be removed by sliding the board rearward (red arrow) by grasping around the decoder clips that hang down. But there's a problem! See the next page...
The bottom of the LED (blue circle) hooks on the frame. So you must lift that LED over the frame while moving the board rearward. But the decoder clips over the motor will also hit the frame (green circle), so flexing the board up and wiggling can help back here. It takes some effort to get this board out because clearances are so tight. With the board out, Kapton tape should be applied to insulate the frame in TWO places. Insulate the frame just above the motor (both sides). Also insulate the metal pad where that LED was catching and causing all the trouble (see photo below).
Here are the stock board and the TCS K2D4 decoder. For our purposes, front is the thin end with the little wings and the fat end is the rear. This is an important distinction in this locomotive since, as we shall be reminded at the end, either the long or the short hood can be front. But for the rest of this install, FRONT will be the typical part of the decoder that has the thin end---which on this Alco locomotive, just happens to be the short hood. Now, this next step is not required for a Plug and Play decoder, but you will thank me if you do it for this particular tight locomotive. Do you remember how much difficulty you had getting the stock light board out? Well, you're going to have at least that much trouble getting this decoder out every time you need to do maintenance on this loco. So since that LED hooks on that metal shelf (red arrow), I gently filed my LED a little bit (yellow line). You don't need much!!!!!! You just want to get that lip off of that LED. Most of the LED is plastic. The actual electronics are in that diamond shape part in the middle (blue arrow). Stay away from that.
Go slow! It goes faster than you think. This is all I was after. Probably 30 seconds of gentle filing. And that was with checking to make sure I wasn't going too far. Now I won't have to flex the board so much in the future.
Time to install. First, with the board oriented in the correct direction (thin end toward the cab where the extra weights are on the frame), place the motor clips on the decoder over the fat part of the frame by the motor and hold it there. Don't let it slip off.
Now, pull the front of the board down so that the wings go into the slots (red arrow). You might need to move the board forward just a bit. The decoder motor clips should still be held onto the frame. When all is in position, the board should be curved and flexing a bit (as it is in this photo). That's why it takes two hands. Flat in the front (middle and right part of photo) and higher on left over motor. Once in position, move the decoder forward (right in this photo). The wings will engage and the motor clips on the decoder will pop off the frame so that the rear of the decoder will now lay flat.
Almost there! Now, we need to get the bottom motor tab under the decoder contact clip (red arrow). Keeping the front wings of the decoder engaged in the frame latches (green circle), lift the rear of the decoder a bit in order to tilt the decoder clips that hang down. I then use a screwdriver or some other tool to tuck the motor tab red arrow) behind the decoder clip. The you can drop the decoder down flat again.
The last major step is to slide the decoder (red arrow) the last little bit. This will cause the rear of the decoder to lock under the latches behind the motor (red circle). The decoder is in place when the rear board is under the latches and the middle board hits the metal ahead of the motor (yellow arrow). That's as far as the decoder will go.
Here is the front LED that I trimmed a little bit. Now it will be a little easier to remove next time. Just look how close the LED leads are to the frame. That's why we needed to insulate the frame with Kapton tape. Any electrical shorts could burn out the decoder. The decoder is now installed. One final check is to make sure the bottom motor tab (green circle) is totally tucked under the decoder clip so that it is as far away from the frame as possible so there is no short. One last Alco thing to do on the next page.
Now, as we said at the start, for the purposes of this decoder, the front of the decoder is the skinny end. Well, in this application, that happens to be the short hood. But this is an Alco RSC-2. Did your road run the long hood forward or the short hood forward? If your road ran the short hood forward, then you are finished. Go run trains. But if your road ran the long hood forward (like all that I could look up), then your locomotive will run backwards. No problem-- Reprogram it! Just tell the decoder that the rear is the front. The solution is in the directions that came with the decoder. Just look at section 1, BASIC CONFIGURATION. The Control Variable (CV) you want to change is number 29. CV29 is a complex variable that actually keeps track of a lot of things by adding them all up and coming to a sum. Normally, CV29 equals 6 (the value set by the factory). Notice from the chart that subsection A is the value for Reversing the direction of the locomotive. The normal value is zero. But if you want to reverse it, the value would be --- add one. So therefore, if all we wanted to do was make the loco run in the opposite direction, we would set CV=7. Finished!