Hi folks, I figured that since I was doing this for about the 4th time, I figured I would document how I installed ESU decoders into my Kato RDCs. This time I am installing a Loksound Nano with ESU sugar cube speaker, though in the past I've done a few without sound. This is an RDC-3; the RDC-1 and RDC-2 are pretty much identical except for the shell. The RDC-4 is overall shorter, but features pretty much the same components and is assembled the same way.
DisassemblyThe first step is disassembly. While you can probably find some existing instructions on how to open up the RDCs, I want to share my method with photos. To remove the shell you only need a single toothpick. Flip the car over and insert a toothpick between the shell and the frame right next to the truck bolster. Kato body shells flex easily so it should be pretty easy. Once inserted, gently pry the toothpick outward; the shell should pop off at this end with very little effort.
Repeat this process on the other end, being careful not to let the first end snap back on (you can insert another toothpick into the slot where the truck snaps in to keep the shell from falling back down). With the shell off it looks like this:
Keep note of which direction the shell is facing in in relation to the chassis. If you can't tell which end is which, usually the roof blister is slightly closer to the "front" end, and that is the end that has the square opening in the interior/floor piece. The next step is to remove the cab & light board assembly from both ends. Like practically everything on a Kato model these are held in by clips, although not very securely and can be popped out with very little effort.
You might notice that I have already installed MicroTrains couplers on these. They accept the 2004 style coupler; to install you can remove the steps & pilot assembly which you can see is held on by clips. The coupler is mounted to these with a clip in the same way it is on a lot of other Kato engines. Underneath the light boards are pairs of contact strips which provide electrical connection to the truck pickups. These should be removed; pull up on the end to lift them off the pegs that hold them in place, then slide them out.
Next the underbody detail needs to be removed. This can be tricky as the clips are hidden, but if you squeeze on the right place and pull it should come off one end at a time. Hold just below the tabs (shown below), squeeze and pull outward.
Once the tabs are free on one end, repeat on the other end until the part is free. The next step is to remove the trucks; these are clipped into the frame and have long universal shafts that couple with the motor shaft. To remove them, rotate the truck fully to one side until it stops. Gently twist it further while pulling it downward on one side and it should pop out of the frame.
With the the clips disengaged, you can pull the attached shaft out of the motor coupling. With the trucks off, flip the car over so that it is bottom up. You'll be able to see that just above each motor shaft is a clip that holds the floor piece in place.
These need to be unclipped. The easiest way I have found to do this is with a blunt pair of tweezers. I slide the tweezers around the outside of each clip prong, squeeze and push upwards to compress the clips and pop them out. These are rather stiff so be careful, and also take care not to damage the couplings on the motor shaft. Also, don't push these up too far. Only far enough for them to disengage, as the floor is still held on in a few other places.
With both center clips disengaged, the floor as 4 more clips (2 on each end) that need to be removed. These are pretty easy to remove, and can just be gently pried off.
With all 4 end clips off, and the 2 center clips disengaged, the whole floor assembly should come off along with the truck pickup strips. These are clipped in place and you can leave them attached. With the floor off the motor simply lifts out from its cradle in the center. Additionally, there's a remaining plastic insert to one side of the motor; I usually remove this as it covers up some space that is useful for cramming wires into. Here's everything disassembled:
Light boardsThe factory light boards are actually made in a way that makes them pretty easy to adapt to DCC installation. They require some slight modifications as I will cover below. First the plastic cab pieces that are clipped on need to be removed. The easiest way to remove these without damaging them is to twist the board slightly clockwise with the plastic piece on the bottom; you'll notice that on one edge there's only one clip. This makes it easier to disengage the opposite clips.
With the plastic part off, it's easier to examine the board. You should notice there are 2 very small screws threaded into some through holes in the board (visible in the photo above). These screws allow the board to be reconfigured for use with DCC. Remove both of them with a small Philips head driver, but don't lose them. Below is a diagram I drew of the circuit, showing also the locations of the holes.
This shows the LEDs labelled R (Red) and W (White), and the SMD capacitor and resistor mounted from the factory. The holes are labelled 1 - 4, with 1 and 3 being where the screws were inserted from the factory. F1, F2, and Common show where I will attach the decoder wires, with F1 being the output for the white LED (headlight) and F2 being the output for the red LED (taillight). You'll also notice 2 other instructions here; remove the capacitor and bridge hole 2. Thus, the next step I perform is to desolder the capacitor that is straddling the leads of the white LED.
This can be tricky to do as you need to get the solder on both ends to flow simultaneously, but I have a tip that is just wide enough to do this. With the capacitor off, the remaining modification needed is to drill a new hole in the board. This hole is just for a wire to pass through, and should be drilled to about a #68 size somewhere where it won't interfere with the circuit. I usually put it above (or below if you consider the other end to be the "top") hole #1.
Finally, I re-insert one of the screws into hole 2 to bridge that trace, and leaving a gap in holes 1 and 3. The remaining holes will then be used to route the wire back to the bottom of the board. Shown below is the "rear" board wired up, with yellow wire soldered to F1, purple to F2 and blue to common, then all 3 wires routed back through the open holes.
With the boards wired up, the plastic cab pieces can be clipped back on. I make sure that the wires are pulled through tautly so there's no interference with the plastic piece. Finally, both boards are reinstalled on the frame, taking care to route the wires through where the contact strips formerly were. This is important because it's the only place the wires can be routed without being pinched by something when everything is fully reassembled.
Motor & track connectionsWiring up the motor & track connections is pretty straightforward. I place the decoder on the "front" end of the car, between the cab and the square hole in the floor. However, before connecting these wires I wrap kapton tape around the track pickup strips where they sit above the motor. I then route the motor and track wires through the hole before soldering them. The motor wires get soldered to the motor leads, which I then trim down so they don't protrude up against the contact strips. The track wires get soldered directly to the pickups. DO NOT solder to the pickup strips without something to thermally insulate them from the plastic floor. I usually shove some strips of kapton between them to protect the plastic from the heat. If you don't then you will very likely melt the floor a bit.
With the track and motor wires all connected, I then snap the floor back into place. I carefully route all the wiring through the openings in the floor; it's especially important ot make sure the motor wires are routed through the clips and not being pinched by them, and are not touching the motor shaft at all. Also make sure you are not pinching any of the wires connected to the light boards. These need to be routed up on top of the floor.
Remaining wiringWith the floor in place the remaining wires can all be hooked up. I like to tape down the wires from the far end of the car along the center of the floor so as to keep them somewhat tidy. In my past installations I included 2 additional 1kOhm resistors spliced in the blue wires from each end, which I shoved into the void below the floor. However this time I decided it probably wasn't necessary and when I tested it the 270 ohm resistors on each board seemed sufficient. So I just joined all the blue wires and shoved them into the floor hole.
For the speaker, as seen above, I took a short strip of 0.03 x 0.04" square styrene and glued it along the centerline of the speaker baffle. This sits in the slot between the large opening and the smaller opening above the motor, keeping the speaker centered. I then tacked it in place with a small amount of black tacky putty.
So it's probably very apparent that I haven't accommodated any interior lighting for these. Well, this is the 5th RDC I've converted to DCC and after the 1st one I kind of decided I didn't really care about interior lighting, and there are 3 reasons why:
- The interior isn't really that spectacular. The floor comes up to right below the windows, so unless you are looking at the car from ground level you're just going to see the floor. And with the DCC conversion you're just going to see the wires if you look into the windows. Adding passengers may help but that's not something I usually do.
- The supplied Kato lighting kits don't really work well with these anyway. The RDCs appear to have been designed to fit an older version of the Kato lightbars that are no longer in production, and the new ones are very, very finicky to fit. And once installed they kinda don't even diffuse the light well anyway. So even if I decided I wanted to add lighting, I would have to find a totally different solution.
- While the Loksound decoders have extra functions available, some of these I've installed without sound and fitted only Lokpilot decoders. These only just have enough functions to operate all the headlight and taillights, so I had no extra functions to use for interior lighting on those installations.
I thought about maybe installing Rapido battery light bars to overcome both issues 2 and 3, but didn't think it was worth the effort. Someday I might change my mind but for now, I'm not bothered.
ConclusionAnyway, I hope someone finds this helpful. This is the first time I've tried to document anything like this and I wanted to be very thorough and include a lot of photos; particularly of the disassembly process, as I've always found that to be most helpful and often lacking in other online tutorials I've seen.
