# Help with Athearn BB and Digitrax DH123AT!!



## sbeck80 (May 14, 2012)

Ok - here's my issue, and I know all you smart DCC'ers have an answer for me. 
I have an Athearn AC4400 blue box that I added the DH123AT DCC decoder to. While I was in there I replace the bulb with an led and added 2 ditch lights using SMD LED's. All wired in series with resistors - I want the ditch lights to come on with the headlight and that's it. 
So it runs on DC just fine with the decoder (I don't have a DCC controller just yet), but I get no lights. I emailed Digitrax and they guy said "The lights will not work on DC unless turned on on a DCC system. They cannot be controlled on DC, only DCC."

And asked if a dummy plug in place of the decoder will make the lights work on DC his reply was "It is a DCC decoder designed for DCC with DC as something it can run on so nothing will change no matter what you do."

Is he full of it or is that really how it works? Also, where does one get 1 single dummy plug? I can't find them anywhere around here and sure don't want to spend $30 for a set of 5 of them. 

Thanks!


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## sbeck80 (May 14, 2012)

And just in case wiring is questioned....I'm going from the white wire to a resistor, to the + led lead of the headlight, - led lead of the headlight goes to the + SMD LED lead of ditch light #1, - SMD LED lead of ditch light #1 to + SMD LED lead of ditch light #2, then - SMD LED of ditch light #2 is going to the blue wire of the harness.


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## Brakeman Jake (Mar 8, 2009)

You're connected reverse.Decoder wiring is contrary to usual electrical conventions...the blue wire is the common positive lead while the white and yellow wires are negative.Then,also make sure none of the LED's is reversed too as it won't let the current go through.


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## Brakeman Jake (Mar 8, 2009)

I was forgetting...I never tried a decoder on DC so can't really tell but what the Digitrax man told you makes sense...lights may still not work,though I think they should.Then if you had the eight pin plug,the lights would work on DC through jumpers within the plug...they get fed directly from track power and you have no control on them.


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## NIMT (Jan 6, 2011)

sbeck80 said:


> And just in case wiring is questioned....I'm going from the white wire to a resistor, to the + led lead of the headlight, - led lead of the headlight goes to the + SMD LED lead of ditch light #1, - SMD LED lead of ditch light #1 to + SMD LED lead of ditch light #2, then - SMD LED of ditch light #2 is going to the blue wire of the harness.


You've got the LED's wired wrong and backwards the wire yellow green violet are all (-) negative and the blue common is (+) positive!
You can not wire them in series they need to be wired in parallel!
All the LED's (+'s) are connected to the blue. The headlight (-) goes to white, Rear light (-) goes to yellow, Ditch lights (-) would normally go right to green and left to violet. but if you just want them to work with the headlight then go to the white.
You also need one resistor per led!

And yes you could run it on a jumper plug, it would be a 9 pin JST plug not a 8pin jumper plug.
PM me if you need one.


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## Brakeman Jake (Mar 8, 2009)

Green and violet wires are "not used" with a DH123 decoder.This is stipulated on the installation instructions sheet.


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## sbeck80 (May 14, 2012)

Well then their wiring diagram sucks! Why can't they be wired in series? Looks like I have some re-soldering to do...
So blue(+) to all + wires with resistors first...white (-) to all -?


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## sbeck80 (May 14, 2012)

So why can't I wire in series with 1 resistor (+ wire to resistor to + lead of headlight...then - to +, - to +, - to - wire)? I've only got a 5mm led and 2 SMD led's. I've read that I can only wire in parallel if all leds are the same. Is that not the case?


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