Athearn Blue Box HO SD40-2 DCC CONVERSION

[upnick]

Hi All,

I decided to put into words and pictures my conversion of an Athearn SD40 - 2 Burlington purchased from Trucklover



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.

Next time i will fit the front and rear LED lighting.

[Sarge]

Thanks, I have a bunch of these. I suppose someday they will get DCC. I will be looking for your light instal as well.

[Trucklover]

Say, that loco looks familiar

COOL!! Thanks for posting this Nick, it will come in handy when i go to convert my Athearn Blue Box CNW SD40-2

[tetters]

I'm finding the more I do these DC --> DCC conversions, the easier they get. Thanks for sharing.

[upnick]

Hi all,

As promised here is the lighting for the SD40 ....... Sorry the pictures are a little out of focus.

I use 3MM LED'S on HO installs though smaller ones can be utilised ........
First off install a 3MM LED holder in the square hole of the front plate shown here where the original bulb lived these are cheap at you local electrical supplier.




Next place the LED in the holder and measure the length of the white lead cut strip and tin it in readiness now you need a jumper wire from the postive side of the LED (the longer leg of the LED) tin and solder a blue wire to it keep with the decoder wiring code long enough to reach the rear LED positive leg.
Thread a length of heatshrink onto the positive lead and shrink down, now add a resistor between the other leg of the LED and white wire solder up remembering to use heatshrink.
Some 3.2 heatshrink over the LED will lessen any light seepage a tiny amount of contact or latex adhesive holds everything firm in the bracket but allow removal later if you wish .



Front LED with jumper wire and resistor installed.
Repeat fitting a resistor with the rear LED inline with the yellow wire this time as here ...... the decoder /front jumper blue wires can be seen .



As before with the red jumper wire tin and twist the decoder/front jumper blue wires together and solder to the positive leg of the rear LED, a drop of glue again will hold the rear LED to the truck pick up top (circled in green) leave enough length in the LED/wires to bend the light up to the body underside, again some 3.2 MM shrink over the LED to finish.



While doing the lighting install i always test the LED's are working at each stage, remember use heatshrink wherever a bare joint occurs and insulate especially where any joins can come into contact with metal parts.

Finally test and enjoy your newly converted loco

[LynnB]

Nice job on the install, I'm interested in seeing how you keep the wires off the turning motor.