This is the third in a series of articles (title above notwithstanding) about getting a Kato KIHA 110 working with DCC. In this first part, I hooked a decoder up to the motor, and got basic functionality going. In the installment, I outlined how wiring headlights for DCC works in principle. In this article, I demonstrate how this works out in practice. The short answer: Sometimes things don’t go according to plan.
So. Let’s get down to brass tacks.
Remove the shell. The black boxes on the left and right house the lightboards and associated paraphernalia. We’ll have to remove the roof details first, then the clear plastic window pieces. The roof details block the windows in, and the windows block the lightboards in.
The two lightboards, the front (left) and rear (right) are attached to the inside of the shell. I’m just going to worry about the front lightboard for now; just repeat everything for the other lightboard. To release it, you’ll have to use a jeweler’s screwdriver to release two plastic tabs along the sides of shell (where the white arrows are pointing).
The lightboard is held in place by a plastic clip; this will come out with the lightboard. Make sure that none of the lightpipes (not pictured) come out too, or at least, make sure you don’t lose them! I had one tail lightpipe that wouldn’t stay put.
Here is a closeup of the lighting circuit; notice that it looks (as it should!) just like I said it would…except…can you see the difference? I didn’t, at least not at first. The light-board is upside-down relative to the diagram I posted before. So, whereas, according to Kato’s diagram, we should remove and reverse the taillights, in fact for this operation, we should remove and reverse the headlight. I didn’t notice this until after I had removed the taillight! So: Lesson! Don’t only memorize what needs to be modified in these sorts of operations, but always pay attention to why the modification is being made. I didn’t!
Anyway, once I got myself straightened out, I removed the headlight and brass pickups. The pickups will be discarded (…into the bits box, anyway), and the headlight re-inserted backwards from how it was. But first, there are traces to cut.
Cutting traces on these boards is easily accomplished with a small set of needle or jeweler’s files. I got my set at RadioShack ten years ago, and they have served me well ever since. I finished the job with some brief attention from my modeling saw. Be careful not to cut all the way through the circuit board, and watch where all those conductive metal filings end up.
The KIHA 110 has lightboards at both ends, but Digitrax decoders only provide one common (or return, or ground, whatever you call it in your local dialect) wire. So it has to be split. I just cut the insulation close to the decoder, pulled the insulation a bit to expose a bit of wire, and wrapped a bit of scrap wire around the exposed portion. Use heatshrink tubing to protect your work (and be sure to slip it on before you start soldering).
I soldered the two wires together, and shrank the heatshrink tubing around the work to protect it. Not much to it, really. Give it a tug to make sure that the bond is mechanically strong.
So, traces cut, wires split, I was ready to wire everything up. Sparing you the boring details, here is the final wiring work: White and yellow F0 leads soldered to the LED cathodes, and the blue ground has been wired to the resistor that connects to the LED anodes.
This is it, the whole enchilada. The decoder, wired to the brass pickups, motor, and two lightboards. I’ve got to cram all this back into one tiny shell!
Of course, with all this extra wire floating around, things might not fit as well as they might. Thankfully, the wires all fit in the lightboard retainer. However, getting the shell back on when I was done was a titanic struggle…a struggle I had to repeat, because testing revealed I had failed to completely isolate the motor shoes, causing a short.
Anyway, I’m really quite pleased with how this turned out. I had hoped there would be room inside the shell to at least partially hide the electronics I introduced, but this is looking rather hopeless. As tiny as these new decoders are, the necessary wiring takes up so much space!
One final note: Since the rear headlights and taillights are wired to F1 and F2 respectively, I had to do a bit of fiddling with the decoder programming to get these lights to operate properly. Since I have a Zephyr throttle, and since the F2 button is a momentary-on switch, and since I had wired the rear headlights to the F2 decoder lead, the rear headlights only come on while I hold down the F2 button. This is no good! So I remapped the F2 lead to activate when F3 pressed and vice versa by setting CV36 to d16 and CV37 to d08. Finally, to get the headlights and taillights to come on when the train is moving in an appropriate direction, I had to reprogram a couple of other CVs. How this works will vary from decoder to decoder, but with a Digitrax FX3 decoder, you should set CV51 to d96 and CV52 to d112. This sets the rear headlights to come on when the model is moving backwards and F0 is on (F0 is the master switch for all lights), and sets the rear taillights to come on when the model is moving forwards and F0 is on.