I decided to put into words and pictures my conversion of the Athearn Blue Box HO SD40-2.
Getting the body off is easy four lugs on the chassis hold it on careful prising of the body away from the lugs with a fine screwdriver had the body free revealing the chassis.
My choice of decoder for this conversion was a Digitrax Z143 four function type a Christmas present from a friend, i wanted to use a four function as ditch lights will be fitted once housings for them are made or sourced using SMD's.
In my conversions i replace any lighting with LED's so the first thing to go was the bulb fitted atop the front bracket prising the plastic block away from the bracket released the bulb.
The next job was to remove the bar running across the top of the motor connecting the truck contacts as this will not be needed,
( i saved the bar and bulb with its housing for anyone who may need them in the future).
Now with a fibreglass stick i cleaned the top of the truck pick up brackets front/rear and the top of the motor contact till shiny.
When soldering i always use flux to aid solder flow ... with this in mind put a little flux on the pick up brackets and motor top and tin with a little solder ready for the wires.
Now carefully remove the motor from the chassis pulling upwards take note of the direction of the motors removal mark with a permanent marker to show its direction within the chassis such as a cross for the front end..... remove the white motor retainers and put aside, the two motor tabs on the underside need removing with clippers to save shorting out on the chassis the picture shows the left hand one removed already ......
squeeze the area the tabs have been removed from with pliers to make sure any remainder of the tab is flush.
Clean the area to recieve the orange wire and flux / tin as before the decoder is to sit atop the motor when finished measure the length of wire needed to reach the motor underside and a little bit cut to length, tin and solder to the motor contact as here .....
A small piece of tape was applied over the soldered joint and the white mounting blocks replaced ...... engage both couplings into the truck couplings and feed the orange wire up there is enough space for the wire to fit between the motor and chassis push the motor down locating the lug mountings in the chassis holes and check the motor rotates freely and is engaged with the trucks.
The Orange wire fed up under the motor.
A red jumper wire is needed to connect the trucks together and decoder to one side of the chassis cut this a little overlength to allow movement in the trucks ..... again flux and tin the wires
here i have soldered it to the rear truck and twisted the decoder red wire around the jumper ready to solder to the front truck.
With both ends of the jumper / decoder red wire soldered up, in the second picture i have superglued a piece of white 40 thou plasticard slightly wider than the motor contact strip to mount the decoder on to with double sided tape.
The Grey wire has been soldered to the top motor contact shown circled in Green.
Now all that remains is to sort the black wire out ...... the front Bracket picks up from the other sdie of the chassis and needs a good clean with the fibreglass stick tinning and the black wire soldering on shown in the final picture.
After a test on the programme track i now have an Athearn SD40 fitted with DCC i hope this helps show how easy this install is.