Wiring to control ditch lights on Athearn RTR

lynngrove Sep 24, 2010

  1. lynngrove

    lynngrove TrainBoard Member

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    I recently installed a Digitrax SDH164D decoder in a HO Athearn F59PHI locomotive using the 9-pin plug on the Athearn RTR circuit board.

    I want to use F1 (green wire) and F2 (violet wire) to control the ditch lights.

    I have read in several places that I can solder wires to the holes on the Athearn board near the green and violet wires to make this connection...use resistors to reduce the voltage in the green and violet wires from 12v to 1.5v for the bulbs...and leave the light common wires connected to the "light common" terminal on the Athearn board.

    Here is my first question...to avoid soldering on the Athearn board, could I just clip the green and violet wires off the Athearn board and solder directly to the wires coming from the 9-pin plug? Is there any reason why the green and violet wires need to be connected to the Athearn board?

    Second question...the Digitrax SDH164D also has F3 (brown wire) and F4 (yellow wire) on the 10-pin plug (that also connects the speaker and capacitor) on the other end of the decoder...could F3 and F4 be used with the "light common" for ditch lights, thus avoiding any bother of the Athearn board or clipping wires?
     
  2. drsager

    drsager New Member

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    Let me begin by saying I have no personal experience with either the Athearn unit in question nor the Digitrax decoder. My post is based on the information I found for the decoder and personal experience with "being creative" when installing decoders. (I couldn't find anything for the Athearn unit, let alone how the board is configured.)

    I cannot answer your first question directly. I can only suggest you try and "follow the flow" on the board for the green and violet wires to see where they lead. Is there anything in between the wire connections and the holes you plan to use? If not, then theoretically you could bypass the board and directly connect the wires from the lights to the wires from the decoder (with the resistors in place). Personally I would just make the connections to the existing board and leave it be. The decoder is plugged into it, no? If that's true then it's not like you're going to get rid of the board.

    Regarding the brown and yellow wires, there's nothing in the documentation for the decoder (other than they are associated with F3 and F4) as to what the wires can be used for. My biggest questions are what is the voltage coming out of those wires, and are they associated with the "common" (blue) wire? While one would assume the answer to the second part is "yes" remember what happens when we assume. ;-P Is there a reason why you wouldn't want to use the green and violet wires? At least with the green and violet you know what CV's they map to (51 and 52, respectively).

    Personally I would recommend you following the directions I found in the Digitrax Knowledge Base on setting up ditch lights - at least that way you can get the CV coding and function keys down.

    Just as an aside, I learned quite a bit doing research for my response. Particularly, while Digitrax has a 12-page PDF (compared to MRC's 2-page for their 1651 decoder) they spend more time advertising than actually providing you with content / instructions on how to best use their decoder. MRC comes right out and addresses how to program their light effects as well as which function key will activate them. But persistence paid off, and I like the fact that Digitrax does have an online FAQ-style area where you can research how to do things (I don't know what I'd do if Frank ever left MRC!).

    hth!

    - Dave
     
  3. temp

    temp TrainBoard Member

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    A big thing with Digitrax documentation is they assume you already have the bound decoder reference manual that comes with their command station sets - the instruction booklet that comes with the decoders is more like an errata sheet padded with advertisements.

    Since it's not linked to in an intuitive place (like on the decoder list!), here is the downloadable version of the decoder reference manual:

    http://www.digitrax.com/ftp/decodermanual.pdf

    The online help you've already found is a great place to find solutions for specific locomotive installations.
     
  4. Coaster amtrak

    Coaster amtrak New Member

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    I came across this thread when I tried to add ditch light effect to the same loco (Athearn F59phi) with the same decoder (SDH164D). Here is how I did it in case anyone asks the same question in the future:

    Cut the Green and Violet (F1&2) on the decoder harness in the middle; solder them back together so now you have a place to tap into the F1 and F2. (Athearn F59's RTR light board does not have soldering pad for F1 & 2.)

    Now solder a 800 ohm resistor on each of the soldering point you just created. This will bring the voltage to the light bulb (Athearn G63843) down to 1.5 v. (Do not use the ohm suggested by the Digitrax decoder manual. You can back down from 800ohm if not bright enough. What digitrax suggested is not for the G63843 and will be near 2v or more sending to the bulb. You will need to replace bulb pretty soon.)

    The Green and Violet (F1&2) is the "-". Now you need to tap into the Blue common (+): You can either do the same on the blue wire on the decoder harness; or, easier, just tap into the blue wire coming out of the sound harness leading to the capacitor. The voltage between the Blue and the Green/Violet is 12 v DC when F1&2 is ON (therefore you need the resistors for your 1.5 v bulb).

    Now take one lead each from the two soon to be ditch lights and solder them together. Then solder that to the soldering point you created on the Blue common. Use heat shrink tube to cover the connection will make easy prevention from shortage.

    Solder one remaining lead from one bulb to the resistor on F1; one remaining lead from the other bulb to the resistor on F2. Cover the entire resistor and connections on both ends with heat shrink tube.

    Program CV51 to 106; CV52 to 107; CV62 to 196; CV63 to 064. This will make the ditch light ON constantly when the headlight (F0) is on. But when the horn (F2) is pressed, the ditch light will flash and will continue to flash for another 5 seconds after the horn button is released.

    DO NOT skip the blue common and connect the bulbs directly between the "+" on the RTR light board (where the headlight connected to) and F1/2. You would think that connection will give 1.5 v without the need of resistors. I tried that and somehow there is a spike of voltage when you turn on and off the headlight (F0) which will burn out the ditch light bulb.

    I have not tried just cut the Green and Violet without reconnect them back to the light board. I don't see why that's necessary but I did it anyway since its not hard to do. Let me know if someone tried it.
     
    Last edited by a moderator: Jul 19, 2012

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