top of page


Download full installation guides here


Left Board

Right Board

1. Remove 5 Screws Holding Turnout Cover

Begin turnout disassembly by removing the 5 flathead phillips head screws holding the cover.  Once the cover is off, parts like the plastic actuator, coil and straight wire point spring may fall out of place if the turnout is bumped or turned over.  The actuator which has a magnet at or near each end will try to pull the coil with it when moved.  Keep these things in mind as you follow the next steps.


2. Remove Actuator and Kato Circuit Board Attach Hardware (4 Hex Nuts, 4 Lock Washers, 4 Screws)

Hold the copper heat spreader around the coil with one finger.  Continue holding the heat spreader and locate the black plastic actuator part running across the lower middle of the turnout.  Lift the actuator by the right end while rotating it counter-clockwise if needed to release it from the copper-toned T-shaped switch.  The actuator will be reused. Next, there are 4 hex nuts with matching lock washers that need to be removed and a single pan-head screw as well.  These parts will be reused.


3. Trim Plastic Actuator Extension

The plastic actuator that was removed in step 2 has an extension to control the T-shaped switch which is not reused.  This extension needs to be removed.  Use flush-cutting pliers to cut along the left edge of the actuator plastic just beside the area where it retains one of the magnets.


4. Remove Kato Circuit Board, Coil, Thermal Switch and Thermal Coupler

Once the nuts, lock washers and single screw are removed, you can lift the Kato circuit board, coil, thermal switch and thermal coupler from the turnout being careful with the 2 fine wires between the coil and the board.  The coil will be reused.


5. Remove Extra Hex Nuts in Turnout Base

The last step in preparing the turnout for the N4 Accessory Decoder Board is to remove the 3 hex nuts  laying in the bottom of the turnout which are no longer needed.


6. Install N4L or N4R Board Over Threaded Studs, Secure with Hex Nuts, Lock Washers and 1 Pan Head Screw

The N4 accessory decoder board has the same size and shape as the original Kato board.  Orient in the same way as the Kato board, locating it by the holes that match the 4 threaded studs.  Use the 4 lock washers and 4 hex nuts from step #2, and 1 of the pan head screws also from that step to attach the N4 board.


7. Slide off Thermal Coupler, Unsolder and Separate Coil and Thermal Switch from Board

Slide the Copper Thermal Coupler off the coil that was removed along the Kato board, coil and thermal switch. Next, unsolder the coil and Thermal Switch from the Kato board at the three solder pad areas which are grouped together.  Do this by holding the Kato board vertically with the coil and Thermal Switch hanging just below it and slightly above your work surface.   This will allow the coil and thermal switch to drop a very short distance to your work surface as the solder liquifies and releases it's hold on the parts.


You will find that the Coil has 1 wire that is wrapped around 1 wire lead of the Thermal Switch.  To separate them, hold the Thermal Switch with one hand and heat the connected wires with a soldering iron by swiping down the Thermal Switch wire lead .  The heated Coil wire will slip off the Thermal Switch wire lead.


8. Prepare Coil and Reinstall

Straighten the coil wires by holding the coil between 2 fingers and lightly pinching each wire separately between 2 fingers of your other hand while running them down the length of the coil wire from the coil body to the end .  The wire is thin and fragile so do this carefully.  Orient the coil so that the wires are closest to the N4 circuit board.


Features molded in the turnout plastic locate the coil so it will not move sideways.  Reference the photo to position the coil at the plastic features.  Use the coil orientation from above. The wires should be pointing straight up at this time.


9. Solder Coil Wires to N4L or N4R Board, Tuck Wires Beside Coil, Reinstall Actuator

The N4 Accessory Decoder is shipped with solder on its pads to hold the Coil wires that attach to them when heated to temperature.  The lower solder pad on the N4 connects to the Coil wire nearest the end of the Coil..  The upper solder pad on the N4 connects to the Coil wire held in place by the white glue spot.  While making the solder joints, hold the Coil's magnet wire carefully with needle-nose pliers or electronic tweezers while heating the existing solder blob on the N4 until it liquifies, then poke the bare Coil wire end into the solder, remove the soldering iron and hold the wire still until the joint solidifies. 


10. Test Solder Joints for ~20 Ohms of Resistance; Check Straight Wire Spring for Center Position

You should test the Coil connections with a multimeter set to OHMS mode by touching one multimeter probe to one blob and the second multimeter probe to the other blob.  The multimeter should read around 18-22 (OHMS).  This would indicate successful attachment of the coil wires.  If you don't see a reading in this range, re-heat the solder joints in the same way as before while holding the coil wire with pliers or tweezers again.

Check the location of the Straight Wire Spring at the left-end of the turnout where that wire moves the plastic part attached to the point rails.  The Straight Wire Spring should rest in the middle of the point rails attachment. Note there are 3 positions where it may land if it shifts during installation.


11. Trim Small Locating Features of Turnout Cover Plastic (for Original Coil Pin Positioning)

In its original condition, the cover of the turnout has a short vertical projection with 2 slots that help to stabilize the coil connection pins that are on the original Kato circuit board.  The N4 Accessory Decoder board has dual pins as well but the separation of those pins is slightly different plus the pins are square and inherently longer.  Though small, the plastic projection on the cover must be trimmed flush with the cover surface.  Do this preferably with flush-cutting pliers.


12. Mechanical Check and Reinstallation of Cover Screws –

You’re Done!

Now manually check the operation of the turnout actuator to make sure it moves the point rails properly.  Put the cover in place and grasp the turnout with one hand, clasping it so the cover does not fall off (the screws have not been attached yet).  Flip the turnout so the rails are on top and slide the manual lever on the turnout to see it the point rails move completely from one side to the other.  If so, you can carefully place the turnout upside down again and install the 5 cover screws to complete the assembly.

Proto Design Labs logo
bottom of page