# Decoder wiring



## Nolackofwanna (Mar 10, 2011)

Hi Guys!
So…being new to DCC, I’ve encountered a bit of an issue that requires some confirmation. I own two DCC equipped locomotives both are Bachmann , one is an SD-40-2 and the other is a DDA40X. I tried running them on a friends DCC system (NCE).
The SD40-2 allowed full programming no problem and runs OK, it will also run just fine on basic DC. The DDA40X would not run in any mode (out of the box) and comes up with a “cannot read CV values” error. Since it’s a newer unit I emailed Bachmann and they came up with a suggestion to “reset” the decoder which it will not do so, I figure the decoder is fubared. (The locomotive runs very well with the decoder bypass plug installed). So I figured on replacing the decoder (Bachmann EZ –command 44915).
I recently bought a Digitrax decoder kit for converting early Athearns to DCC (DH123AT) as I thought I’d give it a try …it contains the wiring do-dads for the Athearn and the DH123 decoder. 
This decoder uses an in-line 9 pin connector , the Bachmann decoder uses an eight pin two row plug and plugs into the circuit board in the DDA40X , it appears the wiring colour code is the same between the two decoders, is it safe to consider that the Digitrax decoder can be wired in to the Bachmann plug wire for wire and that would be it? 
I have yet to obtain the data sheet for the Bachmann decoder but if I’m heading for Digitrax (that’s what is available at my LHS) there’s no point in accumulating data for a system that I won’t use. The Digitrax decoder appears to be dual function like the Bachmann DCC/DC and has a rating of 1.5 amps which should be lots for the DDA40X .
Any info or shared experience with this sort of thing would be appreciated.


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## 93firebird (Dec 25, 2011)

There are converter plugs available from the 9 pin on the digitrax to the 8 pin nmra plug. Just check out the "Bay" you should find one.
http://www.ebay.com/itm/SOUNDTRAXX-...245886?pt=Model_RR_Trains&hash=item1e69ee54fe


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## tankist (Jun 11, 2009)

actually you could have bought the DH123 (the DH123P or PS model )already with 8 pin harness. its couple bucks more. but you could very well solder the "D" that you got to the 8 pin connector you have. or better yet eliminate the bachman board completley, that however will require a bit of effort and going back to DC will not be easy.


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## cabledawg (Nov 30, 2010)

If I remember correctly, the Digitrax and Bachman color codes should be the same. Or at least that's what the Bachmann website shows. So to solder the 8-pin NMRA plug to the 9-pin Digitrax connector should be easy to do. Or you can do as Firebird and Tankist said and just buy the Digitrax decoder with the NMRA plug.


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## NIMT (Jan 6, 2011)

Nolackofwanna,
I personally would eliminate the original decoder board completely. If you can't read or write to the decoder then most likely it's bad! Why would you want to use a good decoder hooked to a bad one? The possibilities that it will cause issues if not now down the line are possible!
I also would use a bigger decoder for that use, 123 and 125 are very small and low amperage, I use a NCE 13SJ in my DD40's and have never had an issue.
That's my 2 cents and yes they are Canadian pennies!:laugh::laugh::laugh:


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## tankist (Jun 11, 2009)

NIMT said:


> I also would use a bigger decoder for that use, 123 and 125 are very small and low amperage, I use a NCE 13SJ in my DD40's and have never had an issue.


you find 1.5A capacity not sufficient? how much that engine pulls?

with that my choce of decoder if i had any bachman to convert would be NCE's BAch-DSL board replacement one. 
but given he already has DH123 i don't see why spend moeny again (perhaps unless the 123 can be used for other engine)


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## Nolackofwanna (Mar 10, 2011)

Thanks for the replies you guys are pretty well up on this stuff!!

Well I just test ran it on DC and it works great, just no forward or reverse lights and that I believe is something that has to be programmed when I set the decoder up on the DCC track. So I read all your stuff and this is what I did. To be sure I checked the current draw on the locomotive with the decoder bypass plug in place, 190 milliamps without a load so that’s pretty low so I figure if it hops up to 500 or 600 milliamps working that should be lots and that’s well within the 1.5 amps that the Digitrax decoder is rated for so we’re good there… I hoofed the original Bachmann board and wired in the Digitrax decoder to the 8 pin plug wire for wire, two wires on the Digitrax decoder are not used (green and violet). I used the supplied Digitrax 9 pin plug 
to the Digitrax decoder taped it up and reassembled. But I will be picking up some of those 9 pin to 8 pin plug adapters..Thanks again!

P.S I will ask my LHS to see if he has any higher rated decoders and if he'll get any with the 8 pin plug already attached.


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