Athearn blue box decoder

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Kevinkrey

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Jul 27, 2006
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Saint Paul MN.
I have been asking around about this here and decided to just give it its own thread. I need to install a decoder in my SD9, since there is no major difference and the SD9 is in the diesel shop for a total overhaul, I figured I could use a GP50 to ask questions (I will not actually give it a decoder yet).

I do not have the actual decoder, but I do have all of the wireing, and if I understand I could install the wires and than buy the decoder and just plug it in. I will be giving the SD9 (and later the GP50 in guage railway leasing colors from which the DMIR recieves temporary motive power) a Digitrax DH126AT decoder.

I have been told I need to insulate the motor from the frame. I was looking at the GP50 and found a metal strip below the motor embeded in the frame. Is this what I need to insulate from the motor and if so how.

This is all I want to know for now, I would like to go at this one step at a time so I can follow.

Thanks for any help, and sorry for the reading, hopefully the rest of the posts will be shorter, I can also take pics as I go to make sure I am doing it correctly, but so far this is my longest post so I feel like I can stop anytime now. :wave:
 
Kevin: I don't know recent Athearns, but...
Is the frame metal or plastic? If it's metal you have a larger job than you describe. You really have to get the isolation or you'll let the smoke out of the decoder. If you take the metal strip out, check with a Ohmmeter that it's isolated.
It may be possible to isolate closer to the brushes; depends on the way it's made.
If the frame is metal, a lot of modellers use latex or silicone caulk/sealant to insulate and hold the motor.
 
You could wire it all up so that it would be ready for a decoder, however if you plan on running it on DC for a while before you get a decoder you will not want to isolate the motor yet.

I am not aware of a metal strip embedded in the frame, but you should be able to throw some electrical tape over it to prevent any contact from being made. The next step would be to either flatten, or cut the small prongs that are on the bottom motor clip. You will want to eliminate any possibility of the prongs working their way through the electrical tape. Or you could just swap the top and bottom motor clips and you would be ok.
 

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Here is a pic of the frame, I believe it is metal, but doesnt look at all like the pic from Freelancer. So, is it metal, and is the strip on the bottom the only thing I need to isolate?
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I have been looking at the directions that came with the decoder, and I am figuring it out. But my only probleem is that there are wires that have no instructions on where to go, the violet and green in specific, the yellow and white are for headlights, but the loco has none, (thats for another thread), and the black goes to headlight post, how does it connect and where do the other wires not used go?
 
Kevin, in the Blue Box engines, the frame is used to connect the left side power pick ups with the motor – that’s why you have to isolate the motor from the frame. The headlight post is connected to the frame, so by attaching the black wire to it, you connect your decoder to the left side pick ups.

The blue wire is the common for the function outputs (white, yellow, green, violet). White is for the headlight, yellow for the rear light, both controlled by F0. Green and violet are additional function outputs, you could use for ditch lights, cab light etc. Green is controlled by F1 and violet by F2. If you don’t want these additional functions, you can simply forget about the green and the violet wire.
 
I got the decoder installed, I have the DC pin from another Athearn DCC ready loco, can I pulg that into the harness on the other loco since all the wires are not going somewhere? Would this give me DC operation for the time being?
 
Roger, not quite, what I am talking about is more of a jumper I suppose, it was plugged in my athean DCC quick plug, I unplugged it, plugge in the decoder and the loco was good to go, but could I take this jumper and put it onto the SD9 for temporary DC running? Heres a pic of it next to the SD9, it will fit, but I dont want to put it on the track if it will do damage.
 

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Kevin are those wires connected together (twisted ,soldered) on the end away from the connector? Or are they connected to the loco?
 
Kevin looking at the picture some more I see the wires are going to the engine. Im not sure what that green thing is but im guessing some kind of loop back that is doing the same as the other clips I showed you. Wait for some one that knows for sure if it will work. Im guessing it should because the decoder plug follow a standard.
 
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