Is this the right decoder?


Hey guys,

I bought a "Digitrax DH123D" decoder for my P2K SD9 the other day and I was very happy when I seen the price was only 20 bucks! On the other hand, unlike the one I seen at the "other" hobby shop which claimed to be "plug and play", this one seems to have a blue plastic covered computer chip (the decoder I'd suppose) and a "e-z wire harness" with 9 wires coming out of it. I have pulled off the shell of my loco to see how it would be hooked up, but the instructions say that "the wire harness connects to the decoder, then the harness is wired to the motor connections"! I'm starting to realize that this is not going to be a 5 minute "plug and play" kinda job, but the instructions make it sound like its easy! Do I have to solder anything or cut wires here and there and remove this or that? Or is it as easy as advertised? This may seem like a stupid thing to ask, but I really want to hook this decoder up so I can run it on the club layout when I join this weekend. This is my first decoder,and so I have never "wired" one, but if someone could give me step by step instructions, or at least someone patient could walk me though the process (preferably someone that is familiar with this type of loco and obvioulsy non plug and play decoder????) I'd really appreciate it! I can post pics if need be! This may seem kinda petty, but I JUST found out about 4 months ago that it is possible to run more than one powered loco on the same track! LOL!:eek: Thanks for any help guys!

I've never DCC'd an P2k (though I own a few), but that does sound like it'll be more then plug & go.
I have decoded quite a few p2K loco's( my fav actually) you might wanna try using a P2KSR. replaces the circuit board proto has in loco.. you also need to change the light bulbs in engine, you'll blow the bulbs. Lights someone at club should be able to tell you.

Also on botton of decoder add a strip of electicial tape to inslulate it from engine. Connect me if you need more help
I'm not sure about the SD9. The decoder you got is not plug and play. You can make it work, but it is not as easy as taking out the light board and plugging it in.

IF the SD9 is DCC ready, then you might be better off getting a decoder that is plug and play.

IF the SD9 is not plug and play, then it is just a matter of wiring it in, and that is not difficult. However, it would help if you had a little background on what the wiring is like.

Here's a DCC primer. IF you scroll down about 2/3 of the way, they have a section on decoder installation. Read it then come back to ask questions.
I dunno about "just replacing the board". Both my E8/9's have this square board up front, thats not decoder sized, you'd have to remove it an solder in the plug, or decoder. The wires are soldered to it.
most of the p2k loco's i have done are GP38-2's, SD45's, SD50's, and SD60's.
On all those the wired are held on by black clips to a plug that itself plugs into board. With NCE's P2KSR you unplug that from the board, take out 2 screws and plug that plug into new board.. Hard to explain without some pics.

As for a E9/9.. I really have no idea never seen one with shell off
Does the light board have a small, black colored block that is plugged into it. If so, you are DCC ready, and need to pull this block out and plug the decoder in. Ok, you said you had a harness with loose wires for wiring direct. You need to buy a Digitrax harness, the type where one end plugs into the decoder and the other into the light board. They come in different lengths and I would guess you would need a short one because of space.

Definitely change out the light bulbs to 12v or higher. Digitrax makes a decoder for low voltage light bulbs, but that doesn't help now. I believe it has a suffix of LO or something like that.

EDIT: Another thought: if you find that there is not enough room anywhere, you can always throw in an "N" scale decoder if its current rating is high enough. 1-1.5 amps will work.
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All of the SD9s I have are DCC-ready. There's a little plug with wires sticking out of it that attaches to the circuit board in the stock loco. That plug will plug into a suitable board made to replace the stock board.

Alternately, if your harness from the decoder has a 8-pin plug on the other end, it'll probably be a male plug, which means it will plug into the stock plug; this will work. If your decoder has a plug with bare wires, then that's a problem.

The NCE DASR is a good choice, but the best is the Digitrax DH163LO, which has built-in resistors for the light package.

I think most of my E7s-E9s don't have a DCC plug in them, so I have to do the hard wire thing. ANd, since I'm time-crunched, never got around to doing any of that. Yet....

well guys,

I just recently got a refund on that decoder and went and purchased the "plug and play" type. Much easier and now I'm very happy. When it comes time for a new decoder, I guess I'll try not to be cheap, unless I am feeling more ambitious! LOL!

Cheap is always good, but that's offset by the time it'll take to make it work on something that is set up for a different interface. Since many locos come 'dcc ready' (in that they have some sort of plug interface), it may be better overall to buy the decoders that are plug and play. You can convert a lot of locos that way.

On the flip side, the ones without a plug can have a plug soldered onto them to convert them to plug and play. If the decoder has a removeable harness (probably like the one you had), you could solder the appropriate 8-pin plug on the end. Have not done the 9-pin JST plug.

I usually save all of the plugless removeable harnesses that I don't use, trim them to a short length, and include them in any loco I send off to have converted to DCC (like brass steamers). The guy who does them charges me a pittance to solder on the 8pin plugs, all at once. This allows me to convert a 9pin decoder to an 8-pin interface.