Digitrax decoder DH123

Model Railroader Electronics and DCC
1

Just purchased 3 of theseDH 123’s.

Installed the first one in a Bachmann Diesel (US Army Camoflauge paint).

I set it on my programming track, and followed the instructions.

No shorts no open circuits indicated. I reprogrammed the Loco, to it’s 4 digit road number. All went well.

Lights turned on and off. I therefore changed wiring, to Ops connectors on the Zephyr, DCS 50.

I placed the Loco thru it’s paces to wit: Address, Fwd, Rev, lights on,off, all went well at first. So,

I wired up a second Loco, an IHC GG-1. Same story… All went well at first.

Without making any changes, I placed the first loco back on the track and commenced to play,

back and forth with it. after a few minutes, the lights would not come on. Same thing with the GG-1

the Loco’s still ran in the proper directions, but without lights.

I switched back to the programming connections, and while rewriting the address to 03, (as a test)

I kept getting a [ d nd] error. Looking this up on the digitrax site, it offers a broad explanation,

“decoder not detected”. these were brand new Locos, and the track is clean.

Now on the GG-1 only the rev light lights. No motor control at all.

I’m confused as to what’s happening… AnyGuru’s have an idea?

Thx.

Stony

2

Did you add resistors to your lights? I believe you blew them up. Try reseting your decoder, go to CV08 and change it to 08. Then reprogram your loco’s address. You still won’t have lights but at least your loco’s will move. As for the GG1 that is kind of weird. I once installed a plug in decoder backwards and only one light would work so possibly that is your case as well.

3

Yes, I added 470 ohm resistor to each LED. I tried them on a club layout today, both ran but on the default address (03) no lights on the Bachman, but there was a single light on the IHC GG1. It would not shut off, when direction was reversed, nor would the other light. I can live without lights, but I still can’t get the command station to detect the decoder. I keep getting error [d nd] (Decoder not detected) I even placed a resistor across the track terminals of the Zephyr, as was suggested in the forum. Same result.

Previously reset the decoder’s default with CV8 after this issue was discovered. Still couldn’t address loco

Wiring was double checked, by experienced club members eyes, and is correct. Still cannot program Loco #.

Will reinstall original incandescent lighting , to check. Will also try exchanging a new decoder chip this weekend. and see if the problem is there.

4

Assuming the system is ok (program track works for other locos), there are only a few reasons for a D ND message. 1) poor connection from wheels to decoder (even dirty wheels will cause this) 2) poor or no connection from the decoder to the motor (the decoder pulses the mmotor to acknowledge program commands, if this doesn’t happen, it can report D ND or D NA (no acknowlegde)) 3) decoder is blown - make sure the motor is truly isolated from the track pickups and there are no loose wires that can contact where they aren’t supposed to. It’s usually instant decoder death if one of the motor wires (orange and grey) touches the track pickups (red and black)

–Randy

5

My [2c] worth. I have quite a few of the DH 123’s and have never had the problems you are having. First on the LED’s, I did a post a month ago about 470 Ohm resistors. Mine where dying way to fast, about ever 40 hours or so. Most people recommend using 1000 Ohm which I am doing now. Not the problem you are having but for future use.

Do you have a different engine you can install the DH 123’s in? I would not install a new decoder into either engine just yet. Maybe a club member would let you install them in one of there engines.

Did you try to program using the club system?

Call Digitrax and see what they have to say.

What mode is your Zephyr program sat on? You might try different modes on the main line, just make sure there are no other engines on the layout.

I can see buying one bad decoder, but not two at the same time.

Cuda Ken

6

Try this it may cure your problem its from digitrax . All other Digitrax mobile decoders

  1. Reset your decoder to the factory settings by going into program mode and resetting the following CVs. (Be sure to reset the CVs don’t just read them back.)
    AD2=03
    CV02=00
    CV03=00
    CV04=00
    CV05=00
    CV06=00
    CV19=00
    CV29=06

  2. Replace the loco on the layout and select 03 on your throttle to run the loco with the decoder.

  3. If the decoder/loco does not respond the decoder will need to be repaired/replaced.

  4. If the decoder responds, set the address to the one you want to use and retest the decoder using the new address.

  5. If the loco responds, check the decoder manual for guidelines on resetting the other CVs before setting any CV values. If the decoder does not respond, check the manual for instructions on setting the address and reset the address.

7

PROBLEM SOLVED, FOR THE GG-1 !!

THERE ARE SIX WIPER TYPE PICKUPS FROM THE FOLLOWER WHEELSET,

3, ON EACH END. THEY ARE:

  1. AXLE PICKUP,

  2. INTERMEDIATE SPRING LOADED WIPER FROM WHEEL TRUCK, TO DRIVER CARRIER,

  3. DRIVER CARRIER TO CHASSIS WIPER…

They look, like they are made of Nickle silver or similar, not phosphor bronze.

After some extensive investigation, with an Ohmmeter, I discovered they do not contact very well that is to say that they have very high resistances, A proper bath with MEK, and a “Q-Tip” swab, the resistances lessened, but not by much.

So…I disassembled the follower by removing one screw on the truck pivot, this releases the follower truck from the driver carrier. I see then a spring loaded pin connecting the axle wiper contact, to the driver carrier contact, and another wiper to allow the driver to follow the rails, contacting the plastic chassis which has a similar metal strip riveted to it. Inside the chassis these rivets, connect a brass strip on to which, the wires are connected to supply power to the respective points.

A piece of stranded wire would have been a much better design!!

MY SOLUTION, :

Was, to solder a piece of stranded wire to each of the wipers, effectively removing, all excess resistance, except for the axle wiper. I had some grain of wheat bulbs, which sacrificed their pigtails for this project. This reduced the resistance to only a few ohms, between the axle, and the axle wiper.

Loco is now responsive to the programmer, and is happily sporting the road number ( 4709 ) for it’s Decoder address.

S

8

Hi Cudaken,

Did not try programming on the Club system, too many people there, and it is a small place.

It is about 8 ft wide, by 39 feet long with a “U” HO scale layout that wraps the walls of half of the facility. (approx 24’ x40’)

The other half of the facility, is dedicated to “O” scale, and is 16 ft wide, by 40’.

See previous post for fix…

Charlie

SC&SOM

9

Thanks Gondola 1988,

I’ll try that with the Bachmann US ARMY Loco, if other methods fail.

Since the GG1’s issues were resistance related, I’ll look at that first.

Charlie

SC&SOM

10

Since the GG1 is now working, swap the decoder with the one from the Bachmann loco and you cna quickly determine if there’s a decoder issue or not. If the Bachmann one works fien int eh GG1, then there’s a wiring problem and the decoder is fine. If it doesn’t, the decoder is blown so double-check the wiring in the Bachmann loco before repalcing the decoder.

–Randy