Arnold N scale BR class 75 steam loco
M1 decoder Installation

 Photos and text by Duncan Nisbet of St Bernardin, Ontario, Canada

N gauge Arnold BR Class 75 Ė TCS-M1 


1.       Changing the normal bulbs to LEDís makes this a slightly more challenging project

2.       Plan your installation carefully.

3.       Extending a short wire is possible, but it is far easier to cut to fit when you are sure of where to go, and how to run the wire.

4.       Test run the installation after the motor is wired and before you wire the lights, a surprise here is more easily corrected.

 The project: 

There are a lot of very good Arnold locomotives available that were built long before DCC came along.  Adding DCC is not difficult if you take care and plan.

There is a fair amount of room in the cab, and lots of room to run wires in the side water tanks of this class 75 loco. 


 The work area:

The frame is quite roomy with an integrated sheet-copper circuit ďboardĒ.

There is one thing that must be remembered, the weight has two resting points (indicated) that must not be damaged or modified. Change these and you risk a short circuit.

There is also enough room in the cab for the TCS-M1.


First impressions:

This is the frame and circuit ďboardĒ.

Note the motor is offset to the right on the frame, this will be useful if installing LEDís, as it provides a place to put the resistors.



The two choke coils connect track power to the motor power clips.

Removing them isolates the motor for decoder installation. 


If installing LEDís you need to remove the front and rear bulb and retaining clips (indicated).

The rear circuit should also be cut back a bit (see the yellow mark), and the small retaining post (indicated) removed or it will get in the way of the wiring for the rear LED. 


The moment of truth:

Test wire and run the locomotive.  It looks odd but is a good idea. 

This test showed that the orange and gray wire had to be connected crossed over from normal practice.

Tape is used to hold things in place during the test. 


The final motor wiring showing the orange and gray connections reversed from what you might expect. 


LED Wiring:

The front LED is not too difficult and by using 3mm LEDís they drop right into the old bulb holder.

You must fully insulate the LED leads, and it is also a good idea to mark the common (the Long lead) before cutting and wiring.

Note the insulation on the front LED.  This is essential as it may touch the body weight when it is in place. Test fit the weight to get the best clearance

Once you are certain the installation is good, fix the LEDís in place; a dab of white glue works fine.

 Hint: Find a good electrical store and buy high quality shrink tube.  Cheap tube melts; good tube shrinks down well and does not burn or melt.  Get a selection of colors in various sizes.  I had to use blue for some of the work, as I did not have white or yellow of the correct size. 


 It proved impossible to use shrink tube to fully insulate the Rear LED wiring so it is kept from the frame by placing it against another wire. 


Hint:  This installation used Golden White LEDís, mounted pointing down.  LEDís are designed to focus the light to the front.  Installing a bit of reflective foil to deflect the light forward helps. 

A better option would be bright white LEDís.

 All done:

The final wired installation.

Two views of the final wiring in place, showing the placement of the resistors for the LEDís. 


The resistors stack neatly at the side of the motor. 


Final check:

A final test fit of the weight to check no wires get pinched. 


The final product: 

Once you are sure everything is fitting and working correctly, it is a good idea to paint the back of the LEDís, the upper resistor and the wires that show in the cab, with some black paint or black marker. 


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