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Sound Decoder Installation into a

Rivarossi  HO
Challenger  4-6-6-4

Current draw of factory headlight:  33mA @ 12V.   Locked rotor stall current:  1.2A @ 12V.

A DSD-2408 sound module was used for this conversion.  Soundtraxx has since come out with newer models of sound decoders. Knock on wood, they have maintained their color coding scheme. Therefore, this installation note should still serve you well. If you don't want a sound module, here is a Rivarossi Challenger with a standard decoder.

This installation note assumes you have read the section on Sound and the section on Wiring Specific Locomotives.  Note that I do not recommend the use of a chuff sync disk on Rivarossi locomotives as covered in the section on Sound.

Be sure you read the Soundtraxx Owner's Manual - especially if this is your first sound module.  The manual contains a lot of good advice.  For the person who has done this kind of thing before, it's still worth reading as I learned a few things, too.  So after you follow the test procedure, take the time to read the owners manual. You can probably hold off reading the Technical Reference Manual until after you have programmed my CVs and you want to make a change.

There are a variety of ways the DSD can be wired and used.  Some of your options involve the F1 and F5 function outputs.  I used them both for the flickering firebox effect.  This is really fantastic.  You may want to use one of these lamp circuits for synchronized flickering firebox where the light gets brighter as would be appropriate when the firebox doors are open and the sound effect of coal being shoveled in is generated.  For more on the flickering firebox see the section on Using Minature Lamps.

If you choose to use both function outputs, Digitrax users will have to make a minor concession because you will not be able to use F1 for the bell function.  (F1 has the bell symbol.)  Some other key will have to be used.  I have brought this to Steve's attention at Throttle Up!  He expects to have a change made to his software in revision 2.0 due out about mid-June or so.  You can map the bell to F5, which is shifted F1, on a Digitrax throttle.  You will loose independent control of F5.  But since I use F1 and F5 both for the flickering firebox, you don't need independent control of F5.  As I said, this is a minor concession.  With so many user controllable sounds, you may want to make a sticker identifying which function key operates which sound anyway.  What a terrible problem to have!

Digitrax Chief owners: Some Soundtraxx DSD modules will not program on some Chief programming tracks.  Make sure you mention you have a Chief when ordering. You will want to get a module that is release 1.1 which is shipping now.  Tell them what you want your short address to be and they will program it for you.  Otherwise it will be their default 03.  All other CVs can be changed in OPS mode on the mainline - which is where you are most likely to program them anyway.  Newer Soundtraxx modules allow you to program CV 17 and CV 18, the long address CVs, on the main line in OPS mode.  Only CV 1, the short address CV, cannot be programmed in OPS on the main.

Don't forget to switch to OPS when you enter programming mode if you will do it on the main.  This is similar to trying to operate something without plugging it in first.  Who hasn't made that mistake?  Also be aware that you cannot read back CVs in OPS mode.

This module is rated at 1 A total including function outputs.  This fact, and given the locked rotor stall current of this locomotive, I would rather have used a 2 A sound module, but one is not yet available from Throttle Up!  But in the interest of science, I went for it anyway after verifying with Throttle Up! that it would simply shut down if overloaded.

You can really tell a problem locomotive when you try to use momentum.  I discovered with this particular locomotive that one of it's universal joints won't stay centered.  So the locomotive occassionally stalls and the module soon shuts down.  Off to the hobby shop for some new joints!

The coupler clank activates whenever it's control bit changes state.  This often happens when the decoder powers up or is reset, which occurs when the above stall problem takes place.  If you have a problem locomotive, and/or you don't care for the coupler clank, you can kill it off.  If none of your function buttons control the coupler clank, it will never occur.

Before You Start:

Let's talk about programming your sound.  You will notice I provided how I programmed my CVs when I was done.  You might be tempted to go ahead and program my suggested values.  Hold your ironhorses.

Right out thg box, this decoder makes every sound it can, at full volume, and begins as soon as track power is applied.  Your spouse may not believe it, but this good.  I suspect that if this decoder can make even one sound, it can make them all.  Still, you will have a reassuring feeling that everything is working if every sound is being produced.  Every time you put the locomotive on the track it will start talking to you.  This is far better for your peace of mind than, "Oh no, what have I done? :(("

If you program all the CVs up front and make a mistake, you won't know if you did something wrong or the module is bad.   Programming my CVs turns down the volume and makes several of the automatic functions manual.

As soon as you have confidence in your new module, or your spouse threatens you, program CV50 to 04.  This will turn the volume down to an enjoyable level - by you, if not the entire household.  Also program CV42 to 80h - which is 80 on a Digitrax throttle.  It may be 128 on some throttles.  This uses the F8 key to mute the module.  These features should restore domestic harmony.  Reading between the domestic jokes, you should note that a 1" speaker with their 1 watt amplifier can produce adequate volume with no problem.

You may also want to program CV53 to 01 - wait for address packet.  This means that except for hiss. your locomotive will be silent until you send it a command - like advancing the throttle, before it will do more than hiss.

Just in case you think you really screwed up the programming, read about CV30 in the manuals.  You can reset the decoder to the manufacturer's defaults - including preprogrammed addresses provided for Chief owners.

Challenger Factory Wiring

Not exactly to Scale!

Disassembling the locomotive:

Initially, the most challenging thing about the conversion is figuring out how to get the locomotive apart.  See the parts diagram that came with your locomotive on how this is done.

For futher instructions on how to get into a Rivarossi centipede tender without a jack-hammer, radial arm saw, nut cracker, or whack-a-mole mallet, click here.

Remove all the wires drawn in red shown above drawing that are not also in the drawing below.  Note which hole the headlight wiring passes through the boiler.  You will need to know this when your replace it with a grain of wheat bulb.

Fortunately, the motor is already electrically isolated from the frame - once the wires are removed from it, of course.  Unfortunately, like many steam locomotives, the head light is grounded to the locomotive's frame.  Use a grain of wheat bulb so you won't have to worry about isolating the exisiting bulb from the frame.

Unfortunately, the Challenger pilot truck walk way is not removable; at least I wasn't able to find a way.  If you follow my tips for the Big Boy and attempt to do likewise to your Challenger, you risk almost certain damage to your Challenger.  Also, when you loosen the power contact for the bottom of the headlight bulb, a steam pipe falls off topside.  Boy, was it a pain to put back!

Remove the bulb contact and it's corresponding wire.  Put the screw and washers back to hold the steam pipe in place.

Preparing the locomotive:

For the flickering firebox, drill out the holes in the middle of the fire door with a #72 drill or something smaller.  This permits a minimum amount of flicker to be seen through the firebox door if you look hard enough.  You may want to drill a bigger hole for a grain of rice bulb and Soundtraxx's synchronized firebox flicker that gets brighter when the firebox door would be open while the sound effect of coal being shoveled in is generated.  I believe this sound is only generated while the locomotive is standing still - as would be appropriate for a large locomotive with a screw coal feed.  For more on this, see the section on Using Miniture Lamps.

Also, drill at least two 7/64" or a little bigger for the wires from the tender and  to let out the light in back of the firebox under the cab floor.  I drilled a total of six in the bottom end of the firebox for the flickering firebox effect.  In the bottom side of the firebox I drilled a few more.  I wouldn't make these any bigger than 7/64" as too much light would be emitted to reflect off of engine parts in the dark.

The tender weight is only attached in the front of the tender.  Drill it out and remove it.

Hot glue the wires of a to a grain of wheat bulb to tender rear headlight lens.  Use a rubber band to hold the bulb while you do this.  For more on installing rear headlights, see the section on installing tender headlights.  Leave the wires a few inches too long.  After the module is mounted in the tender, you may have trouble changing the bulb if you don't.

Replace headlight with a grain of wheat bulb.  Snake the wires through the hole in the boiler that the old head light used.  Before doing so, you will want to make sure at least 3" of the grain of wheat bulb wires are black - they will be noticable if not blackened.  Use RTV around base of the grain of wheat bulb to keep light from leaking out bottom.

Drill the holes for the speaker(s) on the tender floor.  You are fortunate that the front pivoted wheels on the tender offers such a convient mounting area.  A 1.25" speaker would probably fit here.  You could use 1.5" speaker(s), but you will have to trim the frame down.  The Soundtraxx manual shows the hole drill pattern and how to trim a larger 1.5" speaker down.  Be very careful you don't damage it if you are trimming down a 1.5" speaker.  For more information on cutting down a speaker, see the section on Sound.  You will have to use 1" speakers throughout the rest of the tender due to the rounded bottom of the tender.

 I used two 1" speakers in series.  I did this primarily to reduce distortion of the whistle and to reduce the loading on the amplifier.  The speaker is rated at 0.1 watt so it is easy to overdrive with the 1 watt amplifer in the DSD-2408.  You would also get some improvement in bass.  For more information on various speaker configurations, see the section on Sound.

If you are installing a single speaker, bend the fat end of the skinny weight back over the fat weight.  The skinny weight is so, so that it sits in the curved rear of the tender.  Mangle up the other skinny weight.  I used a vice grip to fold the weights back and get them flat.

Using RTV or similar, glue the single tender weight on top of the previous weight pair.  You can also fairly securely "vice grip" them together with the single weight wedged in the fold of the pair.

Using the same adhesive, glue this trio into the tender making sure you can get the back of the tender closed and the speaker on the floor in the front.  No, the weight trio will not sit squarely on the floor.  Using copious amounts of RTV will fill the gap and will hold the weights securely.

Make sure you can get the back of the tender closed and that the speaker will sit on the floor in front of them before the adhesive on the weights sets up.  Glue your speaker in place now using RTVand set the whole tender aside for now.

If installing multiple speakers in your tender, it is easier to use tire weights with sticky foam tape.  I added 3 ounces after the speakers were installed.

If you not being installing your speakers in a way that you can solder to them after they are glued down, solder wires to them now.  You would be wise to do all speaker prewiring now except for attachement to the decoder.  If you want, prewire the speakers and make a splice connection to the purple wire later.  Do this by soldering about 1.5" or so to the speakers and leave them hang for now.  Splice to them later.  As usual don't forget to put the heat shrink tubing on the wire before solder the ends together!  Prewiring the speakers will allow the glue around the speakers to dry without the decoder wires tugging them out of place.  If you choose to solder to the decoder now, set the whole assembly carefully aside and let the speaker glue dry.  Use RTV to glue the speaker in place.

If you will solder wires to the speakers after they are installed, Make sure the speaker terminals on the speaker nearest the locomotive is toward the locomotive.  Soldering to the speaker glued inside the tender is a little difficult.  Note: If you have not read how to open a Rivarossi tender, it is the ends, not the sides or bottom, that come off.  It's like soldering into a paper towel tube.  You will need to solder the speaker, not the plastic sides or your fingers.  The latter never works and always hurts.   Alternatively, you can solder the speakers before installing them in the tender.  It just depends on your soldering ability which way you do it.

Challenger After Decoder Installation

Even less to scale that it was before!

The module actually sits on top of the speakers.  The speakers are located near each end over the pivoting wheels.

Installing the Decoder:

I thought I'd give hooking up the synchronized chuff a try.  I think it would mount best near the middle, gear-driven driver on the rear articulated assembly.  Mounting the sensor doesn't look too hard on the locomotive.  However, I was really concerned that the three wires for the synch sensor would inhibit free swivel of the articulated drivers.  I could be wrong here, so if anyone tries and doesn't have derailment problems, please write me.

If you put more than 1 speaker in your tender, go ahead and weight it now with about 3 ounces of foam tape mounted tire weights.

Cut your wires to your decoder now if you are going to mount a connector on the tender.  Throttle Up! had not yet gotten their 8-pin connectors in yet, and there wasn't another connector that is available that I really wanted to try, so my wires run directly to my locomotive.

If you are splicing to the purple wires or soldering the decoder's purple wires to the first speaker, leave 2.25" on the decoder.  This is the minimum you will need to back the decoder into the tender after you have soldered the wires to the speaker.  This is important!  I had a little less than this and I barely got it in.

Foam tape mount your decoder in the tender.  You should do this now instead of later.  If you want, don't press it down tight.  Doing it now allows you to hook up all your wires while making sure they stay untangled.

Hook up your rear headlight and speaker wires.  Fold up the wires for the synch chuff sensor, put a cable tie on it (no need to put a choke hold in that cable tie!) and tuck it into the tender.

The tender has a nice deck between it and the cab that does well to hide the 8 wires - 11 if you use synch chuff - going to the locomotive.  Blacken the wires for about 3" between the tender and cab.  Mill a small notch in the tender end under the deck near the bottom middle.  This will help hold the wires towards the middle of the locomotive - especially if two of your drilled holes ran together on the locomotive.

Make length of wires going to the cab long enough to use farthest back locomotive drawbar hole if you think you will ever need it.

Wire the decoder wired as shown.  I suggest you leave the wire attached to the front power pickup.  You will need it.  The wire from the tender mounted decoder isn't long enough to reach.  You may solder the black wire to the rear power pick-up tab.  However, these housings are plastic.  If you are not an expert solderer, you will melt it and you will probably short out your locomotive, damage your decoder, and otherwise ruin your day.  It's okay to "chicken out" here.  If you are not sure you can complete the solder connection in under five seconds, start clucking!  It's for your own good!  Cut the wire 1.5" or further from the solder tab on the plastic housing.  Solder your wires to these wires being sure to have slipped a piece of heat shrink tubing on first!

Be sure to use heat shrink or liquid electrical tape, available at placing like Home Depot, to cover the wires and resistors as you tuck your flickering firebox lights in place.  Liquid electrical tape provides more flexibility than heat shrink - something you may need in the fairly tight confines of the firebox.  If you use liquid electrical tape, you will have to be patient and give it time to dry thoroughly.  If you don't you may short out your new toy.  Be sure to read the directions for the liquid electrical tape.

If you chose to not install the flickering firebox and have wires you will not use, take all the decoder wires you will have left over and cut the ends off of them so that there is no exposed wire.  Put all of them inside a piece of heat shrink and shrink it.  Do not solder them together!  While cutting them flush almost guarantees that they will never short to anything, especially the frame (which is tied to one of the wire pick ups), almost doesn't count.  You need a guarantee.  If no heat shrink, then electrical tape - though electrical tape leaves a messy residue.  If you are still thinking about not covering these ends, think of these two things:  How much is that piece of heat shrink tubing worth?  How much is a decoder worth?

CV Settings You May Want to Try

Though not required reading, you may want to read the section on Hexadecimal Demystified.

This is what I settled on for my Challenger for the time being.  I expect will continue to experiment with it for some time to come.

These CVs are for the DSD-2048. They may not apply to a current Soundtraxx decoder.
CV: Value:  Description/Details: 
Short Address - Have them program this. 
Brake. If you are used to momentum, leave this 0 until you are. 

00h Dir 

02h 28/128 & FL control. 

20h Use 4-digit address. 

FL(F0) forward headlight control. 

8xh Automatic dynamo control. 

FL(F0) Reverse headlight control. 
F1 & F5 Firebox control. 
F2 Whistle. 
F3 Blowdown. 
F4  Dynamo control. 
F5 Bell. 
F6 Bell. 

Use 20h to control coupler clank instead. 

F7 Mute. Note:  F7 is a little difficult to use on a Digitrax throttle because of finger positions. 

Try it!  No big deal, really.  Just use F7 for functions you will use less often. 

Use 04h if F7 control of the coupler clank is desired. 

F8 Mute 
Both F1 & F5 Firebox flicker (not adjustable) 

  0Ah  no sync w/Fireman Fred. 

  0Ch  w/both sync'ed to Fireman Frem. 

00-0F Volume 
Background Effects.  1011 1110  F3 Blowdown, boiler pop valve, pneumatic grease gun, Fred, blower, air pump, fast clock effects. 

  x1h Real, not scaled, time for random effects. 

        (x means don't care.  Whatever is there is not relevent to the current instruction.) 

  x2h Air pump. 

  x4h Blower. 

  x8h Fireman Fred. 

  1xh Pneumatic grease gun. 

  2xh Boiler pop off. 

  4xh Auto blowdown.  Otherwise F3. 

  8xh Enable selected background effects. 

Foreground Effects.   1011 Dual air pump, throttle sync, DDE, single expansion articulated. 

  x1h Single expansion. 

  x2h Dynamic Digital Exhaust. 

  x4h Cam chuff sync. 

  x8h Dual air pump. 

  0xh - F0h  Fast - slow bell. 

Wait for addressed packet before turning on sound. 

  00h Sound starts up after power on. 


Auto exhaust sync.  Until I find out the top speed and wheel diameter of a Challenger,
I set this by watching at a slow speed and getting the right number of chuffs. 

00h-3Fh Exhaust tone control. 
00h-FFh non-DDE exhaust volume control. 

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