Installing a DCC decoder in a Hornby N15 King Arthur steam loco that is DCC Ready

Click on each image for a more detailed view

Removing the body from the N15

You are advised to read through all of the instructions below before starting the installation.

This installation really is not difficult as the engine is DCC ready. The most difficult part is refitting the body on to the chassis and getting the fixing screw back into place!

You will need a small Phillips screwdriver for the screw used to secure the body to the chassis.

Before installing a decoder in any loco it is advisable to check the current being drawn by the loco.

If the loco is brand new you will need to first remove the two metal plates used to secure the position of the loco in the packaging.

The body is secured to the chassis with just 1 screw at the rear.

When the rear screw has been removed, pull the rear of the chassis down and away from the body. There is one large lug at the front of the chassis that secures it in the body. You need to pull down slightly at the rear and away from the front to remove the chassis from the body. This can be extremely difficult as there is no space between the motor sides and the chassis, and it is necessary to handle the body with care to avoid breaking or bending delicate parts.

When the two parts had been separated from this particular model it was clear that the tape securing the wires on top of the motor was too long and the thickness of the tape was preventing easy removal of the chassis. This was therefore trimmed back to the top of the motor to make refitting the chassis easier.


Location of NMRA socket and hidden wiring


The loco is DCC ready, having a socket installed in the middle of the loco. Gently lever the dummy plug out of the socket.

There is one capacitor located under the DCC socket. This should be removed if you find that the loco does not run as well as expected once the decoder has been installed. On this particular occasion it was decided to remove the capacitor during installation.


N15 showing location of capacitor

The wiring here is extremely short and the legs of the capacitor were not exposed on this particular model. It therefore required extreme care in removing the capacitor so that other wires were not severed.

N15 showing location of capacitor

A precision cutter was used to cut away the capacitor.

Once the capacitor has been removed be sure to tape up the bare metal left behind or else there is a danger of a short circuit when the wiring is tidied up under bottom of the DCC socket.

N15 showing TCS M1-UK fitted

There is very little space inside the loco so you will need a very small decoder. This installation used a TCS M1 UK decoder, one of the smallest decoders on the market, with a short harness for UK locos. **

Firmly push the plug attached to the decoder into the socket, being careful not to bend the pins. Make sure the decoder is correctly orientated, with the orange wire at the bottom right .

It is suggested that you do any programming of the decoder, before replacing the body.


N15 showing TCS M1-UK fitted

The front of the boiler has a weight in it, which Hornby have thoughtfully cut a block out of in order to fit a small decoder. However, the weight is metal and even though the block is insulated from the chassis by the plastic of the body, the decoder will need to be insulated to avoid shorting out components on the decoder within the block space. Fortunately TCS decoders all come fully insulated, but with other makes it might be necessary to insulate both sides of the decoder.

There can be issues with insulating some decoders as the recommendation is not to insulate because of the heat they generate. You should check with your decoder supplier.


** Since this installation was completed TCS have released the DP2X-UK decoder. This is a plug and play decoder with no wires that sits over the DCC socket and fits well in this loco, the decoder having been designed to fit most UK RTR steam locos.

Back to DCC Installation Index >>

Back to DCC Page>>

Copyright Bromsgrove Models