Introduction

The Kato No. 4 switch contains an inbuilt motor contained within the base of the of the unit. The motor can be operated via the standard Kato switch control unit, or manually via the little slide switch on the unit. As the switch unit contain a built-in motor the conversion to DCC is fairly straight forward, these instructions show how to fit a Digitrax DS51K1 Stationary Decoder onto the switch.

This decoder has the advantage in that its size allows it to be fitted into the base on the switch unit with no trailing connections, so that for people who don't have a permanent layout the track can still be disassembled without worrying about the decoder.

1. Removal of the Base

Start by turning the switch unit upside down onto a flat, clean surface. As can be seen in Figure 1, the base is held in place by 5 'star' headed screws. These should be removed carefully using a T6 screwdriver, and kept in a safe location for reassembly. Then lift of the base plate from the main body of the switch unit to reveal the inside, taking care not to tip the main body over, or catch the fine wires on the switch motor.

2. Base Modification

In order for the decoder to fit flush within the base, it is necessary to trim away part of the base unit, as shown in Figure 2. I trim away this material by carefully slicing away the material using a very sharp craft knife, and then cleaning it off with a small grinding wheel on a model drill.

The pins for the Kato switch connector should then be removed from the circuit board. This can be done unsoldering each one in turn and gentle lifting them from the board. Care should be taken to ensure that the older does not cross between the 2 strips on the circuit board.

3. Decoder Connections

Four connections need to be made for the decoder, 2 to the track power, and 2 to the point motor. The four locations on the circuit board shown in Figure 3 should be cleaned to enable a clean solder joint. The wires fro the decoder should then be trimmed, and the end's tined with solder, so that when the decoder is laid into the corner of the switch unit, next to the circuit board, they reach the four indicated locations.

Then starting with the point motor wires, the Grey & Orange ones, these should be soldered to the locations from which the pins were removed earlier, see Figure 3 for the order. These reason for doing these first is that they are the shortest wires. Care should be taken in stripping the wires in that the insulation can easily come off from the wire due to the short length that the wires would be cut too. Next, the 2 track leads should be soldered to the board in the locations indicated.

4. Programming The Decoder

The decoder is no ready for programming. Connect the track section to the 'programming' track that you intend to use to set the decoder address, but do not yet apply power to the track. Temporarily connect the yellow wire to the same part of the circuit board as the black wire from the decoder. You can know apply power to the track. Using your throttle, select the address you want to program into the decoder and press either c (closed) or t (thrown) to operate the turnout and program the address.

You can now disconnect the yellow programming wire from the track and fold it away so that it can’t make contact with the track. You can now replace the base of the switch unit, replacing all 5 screws. The switch unit is now ready for use and will respond to the address programmed earlier.