Installing a DS51K1 decoder in a Kato #6 and #4 switch

[David]

[Update April 2011 - finally did a write up for last years photos of the #4 installation (scroll down a few posts). Also added a note about power routing on the #6]

This is a basic tutorial for installing a Digitrax DS51K1 decoder into a Kato #6 N scale turnout. I am new to DCC and soldering myself, but found this straight forward and easy install to do – one of the best introductions to hardwired decoders.

What does this do?

With this decoder installed your turnout can be operated from any DCC throttle/system that supports accessory switches. The turnout can still be used with a DC layout; however you won't be able to operate it remotely anymore, only manually.

What alternatives are there?

From Digitrax there are two main decoders: The DS51K1 (today's install), which is about the size of a Z scale decoder, and the DS64, a large unit you mount somewhere on your layout and which can control 4 turnouts. Price wise they are identical.

DS51K1: Good for temporary layouts
-   Can be installed right in the turnout - no wires!
-   Cannot power the Kato double crossover

DS64: Good for permanent layouts
-   Can control up to 4 turnouts
-   Can power Kato double crossover
-   Can power 2 wire (solenoid) or 3 wire (motor) remote switches
-   Can be connected to track power, or use a separately purchased wall wart
-   Can optionally be connected directly to LocoNet
-   Requires 5"x3"x2" area for mounting

The hardware

In figure 1 you can see the decoder and our #6 turnout. The turnout is power routing and uses a 2 wire solenoid to flip the switch. The decoder is about the same size as a Z scale decoder and has 5 wires:

Black and Red: Rail A and B. The black wire is special (see below)
Orange: This replaces the black[Kato] wire
Grey: This replaces the red[Kato] wire
Yellow: This is used to program an address. Touch it to the same rail that the black wire is connected to (this is why black is special), then open or close the address you want. The decoder will remember the last address used while the yellow wire was hooked up.

There are two places the decoder can fit – there is just enough space inside the metal enclosure, but if we place it there we make it a lot harder to program, as well as to install. The easier place to install it is the big cavity under the straight route (upper right, or skip to the last picture to get the idea).

Disassembly

Start by removing the two screws on the back of the metal panel (a small Philips screwdriver will work). Once the screws are removed (and you put them somewhere safe), you'll need to flex the metal cover from the middle – as in figure 2, there are little metal tabs on both ends holding it on. You'll likely use something like a flat screwdriver to give you leverage, just be careful not to poke it too far inside where you might damage something.

You now have figure 3. You'll probably want to cut off all but the last inch of the black and red wires so you can set aside the metal cover. The cable and its connector can be reused in other Kato applications (for example as a jump port cable to connect a Kato throttle to a Digitrax Zephyr).

Here is a quick run down of what you can see in figure 3:

The large black piece is the main mechanical element. It is moved back and forth by the solenoid (the copper coil on the left) repelling and attracting the two permanent magnets. You can easily see the outline of the right magnet.

When the black element is moved it pushes or pulls the T shaped metal element on the right. This metal element creates a bridge between the straight or curved outer rail (the large pads on left) and the correct outputs (large pads on the right), giving the frog and points the correct polarity, and powering up the correct inner rail (the other inner rail is left unpowered, allowing locomotives to stop on the off track).

A critical component is the long metal pin which is used to guide the points. It is connected to the points on the far left, runs under the black shuttle and should be set into the little hole highlighted in figure 4. Normally when you take apart the turnout this pin will come out of the hole – remember to place it back in before reassembling the turnout.

The black and red wires are soldered to 2 small pads (the ones covered in solder) – as far as I can tell the pads themselves are just a convenient soldering point, they do not connect to anything else on the board. The thin end points of the solenoid are also soldered to these pads, forming the electrical connection.

Preparation

First you'll need a small file to make an opening between the interior of the switch and the underside cavity on the diverging end. See figure 5 where I have filed one out. This will need to be big enough for 4 of the decoders 5 wires to pass through.

Next position the decoder in place (maybe use some masking tape to hold it in) and measure out the required length of the wires based on the following:

Red wire should connect to the larger of the two track power pads (the straight outer rail).

Black wire should connect to the other track power pad (the curved outer rail). The reason for this is to make the correct rail easy to reach for the yellow wire.

Grey wire should go to the pad where the Kato red wire is right now (the same pad that has the solenoid lead going to the middle of the solenoid).

Orange wire should go to the pad where the Kato black wire is right now (the pad where the solenoid end point lead is going to)

Soldering

This should be easy, even if you are just figuring out how to solder like me. Everything has nice big pads. The red and black wires from the decoder should be dead simple. The orange and grey wires require some juggling – you must desolder the Kato wires, and the solder on the decoder wires, without losing the solenoid wires in the process.

You can see one of my terrible examples of a completed job in figure 6. Of the three switches I wired up, all of them had mistakes given that this was my first time (including cutting a red wire way to short and having to solder it back together). However the whole thing is rather forgiving – on the first try I had no reference for the orange and grey wires, so I ended up with a switch that worked backwards (close button caused it to flip open) and had to swap the wires. The second switch wouldn't work and I had soldered and unsoldered pieces a few times before I got it right (the power wires, which looked soldered right, seem to have been the issue). And of course the last switch was the reverse (2 lefts and 1 right) and I thought I could just use my diagram and flip it in my head – I ended up measuring the red wire to the pad on the wrong side, resulting in a hasty repair operation.

Reassembly

If you want you can test the turnout before putting the cover back on. Leave it upside down on the table, wire it to your controller with the yellow wiring touching the outside curve rail, and program an address. The black plastic piece should move back and forth on command if you've done a good job.

Before attaching the metal cover make sure that little pin I mentioned is seated properly. Stuff the wires into the cutout you made and slide the tabs for the wider end of the metal plate on first (the side that covers the wires). Then just flex a bit to get the shorter side in. Screw on the plate and test – even if you tested the wiring and it worked, you'll want to make sure the pin didn't come loose when you put the plate back on,

When you are happy a little white glue can be used to attach the decoder in the little cavity as in figure 7. The yellow wire can be slipped under another one to hold it.

Extra note about power routing

If you've looked at the Kato Custom shop picture for the #6 you'll notice some extra blue wire soldered on. What they've done is "turned off" the power routing, which is useful for DCC operations. All this requires is to solder a link between the upper left pad and lower right pad, and the lower left pad and upper right pad - you are duplicating the link that would be formed by the T component, only on a permanent basis.

[Webskipper]

Thanks David!

Kato Custom Shop in Japan somehow decided to show the world how they did it. They also show the #4 and Double Crossover.

Bet yours is bullet proof. ;)

[David]

The extra wires in Kato's #6 wiring simply 'turn off' the power routing function by linking the inner and outer rails with permanent wires. The frog will still be live, so trains entering from the wrong direction will cause a short (I prefer the #4 for DCC because both power routing and the frog can be turned off).

[nik_n_dad]

I've been using the NCE switch kats, which have been pretty solid (but can't be embedded into the turn out)

[keiman]

Will the instructions below also work with the Tomix Points ( all 2 wire PL/R 140 -30) ?
Just need to wire 3  points  on a spur to the tram barn as per my new  proposed Tramway layout.
Am happy to use any make of decoder as I don't have any of the Tomix operating switches.
Have to mount the decoders under the board as not enough room in housing.

[David]

Yes, you can use this wiring for the Tomix 2 wire switches. The only catch is that I'm not sure if Tomix uses the same polarity as Kato - commanding the decoder to open the switch may instead close it, and vice versa. If that happens swap the grey and orange wires.

[keiman]

Yes, you can use this wiring for the Tomix 2 wire switches. The only catch is that I'm not sure if Tomix uses the same polarity as Kato - commanding the decoder to open the switch may instead close it, and vice versa. If that happens swap the grey and orange wires.

Cheers David.will check it out and report back when first one converted.

[David]

After a long delay I'm posting the #4 switch installation.

First some background: The #4 is a newer design from the #6 featuring a much tighter, more factory like design then the #6 and its loose wires and big solder pads. It is also a lot more complex. Each point rail is powered individually, which means they won't cause shorts, and the frog power and power routing can be switched on or off by moving 3 Philips screws from one hole to another. The English labels for the power routing screws are labeled backwards – they come out of the box configured for power routing, but the label claims that those are the spots for non-power routing. For DCC I would suggest switching the position of all 3 option screws, turning off power routing and the frogs power – the frog is small so very few trains are going to have trouble with a dead section like that, and it allows trains to enter intentionally or accidently from the wrong route without causing a short.

To start installing we need to remove the back panel. You'll need a #7 Torx screwdriver or bit to do this and there are a total of 5 torx screws to remove (don't touch the Philips screws except to swap their position). Once the torx screws are gone the plastic backing comes off – it's a flush fit to the rest of the switch.

Inside you'll see a circuit board (Figure 1) with a familiar rotating t component and a compressed black shuttle mechanism and solenoid. There are 4 nuts screwed into the board – each post connects to one of the rails. The frog is connected by a Philips screw that is not visible until the cover is removed. You can also now see how the option screws work – in one position they do nothing, just sitting on a piece of board, but in the second position they bridge a gap. The t is more complex then the #6, and includes 2 layers to deliver the chosen polarity to all the right places. Figure 2 shows the posts and screws labeled (the option screws are in my preferred DCC position, power routing and frog power off).

Installing the decoder in this switch won't be difficult from a soldering point of view, but will require some very close cutting of the wires – there is absolutely no vertical clearance for extra wire once the cover is put back on.

The first step is to unplug the cable – take note of which pin the black wire on the cable connects to, it is different depending on if you have a left or right switch. If you don't have it plugged in to start, plug it in with the Kato logo facing you as in Figure 1. The next step is to take your soldering iron and remove the 2 pins. Hold the end a the pin with pliers or teasers and then touch the iron to the solder to losen it. The pins are not straight – they actually have a kink that rests in a hole in the board. This is how they are installed in precisely the same place every time. The kink won't get in the way of removing them though and they'll pop out as soon as the solder warms up.

Next fit the decoder into the cavity where the plug used to go. Because the red heat shrink varies from one decoder to the next you might need to wiggle some of them to smooth out any "bubbles" or tiny folds in the heat shrink. With any bubbles pushed out the decoder will fit snugly in the slot. Unless you want to make life difficult you should insert the decoder so that the grey wire is on the same side as the pin that connected to the red cable, and the orange wire is on the side that had the black cable. On my decoders this was always with the Digitrax label up, but that could be a coincidence.

Now you need to make your first very close cut, shortening the orange and grey wires so that they can be soldered to the pin pads with no extra wire (orange to black pin pad, grey to red as we already positioned them above). I would suggest making the wire that will go closest to the edge (grey wire in Figure 3) a bit longer then the other, so that you don't need to put the iron right beside the connection you just made. Solder the short wire first, then the long one.

Next up is the black and red wires which need to go to the track power. Since it doesn't matter which is a "rail A" and "rail B" you should wire it based on which wire is closer, so you don't need to cross them (for the same reason as not crossing the orange and grey, there just isn't much height clearance). Unlike the Kato Custom Shop we are going to attach these wires so that the power routing screws will still work. These means we need to attach them to the locations marked as outer straight and outer curved rail which will take one wire on a bit of a journey.

While you can solder them if you want to (be careful soldering near the outer curved rail point which is right beside the mechanism) I did something different. We'll start with the black wire which, because it is closer to the edge, will be connected to the post marked "Outer Curved Rail". I very carefully measured how much wire was needed to reach the post, then cut about an inch after that and stripped off all of the extra (see Figure 3 again). Then I loosened the nut and wrapped the wire around the post under the nut, tightening the nut to hold the wire in place. When tightening the nut you need to use a finger to hold the wire, otherwise friction will try to wind up the wire (very bad). The other wire (red or black) follows an interesting route to avoid running afoul of the space restrictions made by the guards molded into the lid that go around the option screws. The process for securing it is the same.

At this point all our wiring is done. We can cut the yellow wire shorter, program the decoder (same process as #6) and then use some kapton tape to seal the end (of the yellow wire) and tuck it in near the black wire (or red if that's the one taking the less scenic route).

However we now need to make some modifications to the lid. As in Figure 5 we need to use a file to remove 3 portions – we need to remove all of the lip that was previously around the pins (to make room for our 5 wires) along with a tiny bit of the corner and we need to make 2 openings for our straight rail wire (the red one in this install) to exit and then reenter the circuit board area, using the channel previously meant for the switch wire.

With these modifications to the lid it should fit like a glove again – if it doesn't check if you need to file off more or a wire is hitting one of the option screw guards. Reattach the lid (you saved the torx screws right?) and you have a complete DCC switch as seen in Figure 6. The decoder should snug by itself, owing to the tight fit and very short orange and grey soldered leads.

[CaptOblivious]

I've heard that about the English labels being reversed. Is that true for all #4's, or just a particular batch of them?

[KenS]

That was certainly the case when I bought some two years ago, and the reports online go back several years, so I don't think it was just one batch.  Note that the screws only affect the frog and middle rails. The outer rails always remain live, so you still need to insulate them if you're wiring a reversing section.

I don't think this is a mislabeling, but rather a different usage of "power routing" to mean that power is always routed to both, rather than the usual English-speaking model railroader meaning of power is only routed in the direction of the switch.

However, Kato used to have a page about this on their site, which is no longer there (a 404 error is issued for the old URL from any of the sites that used to link to it). So it's possible they've changed this in a new edition.

There's a table describing the operation of the screws on this site (scroll down to #2-19b).

[dennisoommen]

Hi there,

My first post here. Merry Christmas everyone !

Planning to install this in my #6 Kato turnout. Wanted to check to see if I can still keep the original Kato switch cable there........and use it with the conventional Kato switch controller.

Also, if that's possible, can I use both ( the Digitrax DS51K1 AND the std Kato switch controller ) together ?

Sorry if my Q is a bit 'dumb' - not that clued in to DCC.

Thnx,