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Sound Decoder Installation into a

Bachmann HO GS-4  4-8-4

(SP Daylight 4449)

Current draw of factory headlight:  31mA @ 12V.   Locked rotor stall current:  1.3A @ 12V. Current draw of smoke unit: 161mA.

A Soundtraxx DSD-150 sound module was used for this conversion.  This module is rated at 1.5 A total including function outputs.

This installation note assumes you have read the section on Sound and the section on Wiring Specific Locomotives.

The construction of this locomotive has a basically clever design. It can be a real challenge to get apart if you don't know all it's secrets. I'll share those with you. This locomotive is not fun to reassemble after you are done wiring. Stick with it. 4449's pleasant whistle, the synchronized chuff, and a good speaker make this model my favorite to date. In the end, it was worth it.

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 F1 for the mars light and F5 for the flickering firebox. Since this locomotive is oil fired, you will have to pass up the urge to use the synchronized firebox flicker with Fireman Freddie shoveling in coal.  You will just have to put sound into another one of your locomotives.   For more on Mars lights, see the section on Using Miniature Lamps.

Digitrax users will have to make a minor concession because you will not be able to use F1 for the bell function.  (F1 has a bell next to it on a Digitrax throttle.)  I have decided to use F3 for the bell; which is right next to F1 on a Digitrax throttle.

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.

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 the 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.

Disassembling the locomotive:

The split weight provides the electrical path picking up and supplying power for everything the locomotive needs. This clever arrangement necessitates the need for you to isolate the motor from the weights. It's easy.

After you remove the body, remove the screws that hold the plastic underbody and drive wheels in place.

Before going any further, use a marker to mark the motor with a "U", for up, before removing it. When you go to reassemble the locomotive, the motor can go in two ways. If you get it wrong, it will run backwards. You will find that after you successfully reassemble it, you won't want to have to take it apart to flip it over.

Removing the plastic underbody is trick #1. It's front edge is hooked onto the weights. Lift from the back. IT will be bending. YOU will be praying I know what I'm talking about! At the same time you are lifting, be pushing it forward. It will sure act like you have not removed all the screws. Keep pushing (and praying if you wish) and it will eventually pop free. Whew!

By now, you will have noticed that the weights are held together by screws. Opposite the screw are rectangular plastic nuts of sorts. Between the weights are plastic spacers that keep the two weights from touching and shorting out the track.

The plastic nuts and spacers snap together. It would seem they would stay that way when you go to reassemble your locomotive. Instead they may frustrate you by coming undone at the moment you need them to stay together.

There are three of these plastic nut and spacer assemblies. One of them is behind a drive wheel. This is secret #2. If you tried to remove these plastic nuts BEFORE you removed the plastic underbody, you would not have seen the third nut assembly and may be wondering for quite some time why you can't get the locomotive apart.

Preparing the locomotive:

You will find you have a number of things to glue as you install sound in this locomotive. After drilling and cutting your chuff disk you will need to epoxy it to a driver. I did so to the left driver with the gear on it.

You will need to glue the piece of circuit board to the bottom of the drive wheel plastic underbody.  Use epoxy, not Liquid Nails.  I found Liquid Nails won't hold it.  I glued the piece of circuit board between the third driver from the front.   First locate the circuit board aligned and centered with the third driver.   Now move forward about 1/4" (6mm).  Epoxy it here.

You will use grain of wheat bulbs for the front and rear light and the Mars light.   For the bulbs I had, I used a 1/8" (3mm) drill bit.  I turned it with my finger tips from the inside.  Use a sharp bit so that you can do this quickly in the cramped space inside the shell.  My bulbs have a small plastic sheath near the back that I needed to remove with a sharp knife so they would fit in this hole.  The next common drill size up was too big.  Note: I could have found the correct drill size had I gone looking for a very well stocked hardware store or industrial supplier.

Put something in front of the shells as the glue holding the bulbs in dries.  I used Liquid Nails latex glue.  As it turned out, this glue had the tendency to push the bulbs forward as the glue dried.  When I came back later, the bulbs were sticking beyond the front of the lamp housings.  Ahhhhh!!!!  Fortunately, the glue hadn't completely dried.  I was able to push them back, put something in front of the shell, and let the glue finish drying.  I used a video tape slid against the locomotive.  ATV (silicone) adhesive, hot glue, or epoxy should also work for holding the lamps.  Just watch the drool from hot glue.

Lastly, I thought the metal side of the weight MIGHT wear down the chuff disk over time.  So I glued a thin piece of styrene to the weight.  Run the knife blade over the edge of the cut sheet.  This will keep the sharp edge of the cut sheet from ruining the chuff disk.

Prepare your tender bottom by removing the weight and drilling your speaker holes.   Screw down the speaker.  Cut the weight into pieces and epoxy it back to the tender bottom.

Now go to bed.

The Next Morning:

Before you go to work, put a dab of conductive paint on the chuff disk so that is electrically connected to the axle. I had tried to see if I could get the chuff disk metal to make electrical contact with the axle without the paint. It didn't work.

Soldering to the axle instead of using the conductive paint may be possible. Be sure to clean the axle of all lubricants first. As much as I prefer to solder things, I was afraid I might damage the axle. The conductive paint offers an easy approach that will work on all locomotives for everyone. For more on using conductive paint, see 11-17 in Sound section.

Now go to work. Try not to spend too much time day dreaming about your new toy. Don't run over any coworkers as you leave to come home.

Smokeless Oil:

Smoke is cute, but not an essential element of my modeling experience.  Since I like to operate, as opposed running in circles, having to add smoke fluid is a nuisance.   So I have removed the smoke unit from locomotive.

Actually, first I tried to add a switch to it so I could turn it off.   Unfortunately, I broke the smoke unit with what seemed no effort at all.  Then I said, "Fine! Who needs smoke anyway!"  THEN I permanently removed the smoke unit from my locomotive!

If you want to retain smoke capability, there are only two things you need to do.   One, don't fool with it.  Two, reinstall it just as it came from the factory.   You will have full power smoke all the time running straight from DCC track power - even when the locomotive is stationary and you are not using it.

For me, it's the constant on that I didn't want.  Be very careful if you choose to fool with it.  As I attempted to unwrap one of the wires from the side posts, the "glass" rod the smoke unit is wrapped on came off it's mount.

Installing the Decoder:

Power pick up for the decoder comes from the split weights. Use the screw on the right for the trailing truck. You will have to drill a hole on the left side and use a self-tapping #2 screw. You can use a round head screw, if you wish, and still get the shell on. You will find the weight puts up more resistance to your tapping efforts than you would first think.


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R1, R2 = 22 ohms.  C1 = 1000uF

I drilled several small holes in the underbody back end for the wires.

The weight fills the shell well, leaving little space for excess wire. Still, don't cut yourself short. If you make a mistake in attaching a wrong wire (especially to the motor), or break a wire while stripping it, you may not have enough to work with.

Leave plenty of excess wire attached to the headlights so that you can work on the locomotive with the shell off. Alternately, you might want to use connectors. There is very little space for them. If you try and succeed, please let me know.

You will need to use resistors in series with the mars light and the flickering firebox. I managed to fit them both in the locomotive. In retrospect, you can put them in the tender just as well.  You will have more space there and make things a little less cramped in the locomotive. Make sure you put heat shrink over them BEFORE you attach the last wire.

Install your speaker.  For a locomotive with a tender this large, I highly recommend using the Intervox speaker. For more on the Intervox speaker, see 11-16 in the Sound section.

The Soundtraxx documentation shows a 50uF capacitor for C1. See 11-19 in the Sound section on getting slightly better bass from your Soundtraxx unit by using a 1000uF capacitor.

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.

The tender has a nice deck between it and the cab that does well to hide the  wires going to the locomotive.  Mill a small notch in the tender end under the deck near the bottom middle.

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.

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?

For more on Mars lights and flickering firebox, see the section on Using Miniature Lamps.

You will need to break/cut off the long, thin tabs on the motor. This electrically isolates the motor from the frame - which is essential for DCC decoders!  Keep the round electrical connections.

Leave enough excess wire going to the motor that you can cut them and swap them if you got them wrong.  You can also set the direction bit in CV29.  I'm not quite sure how this will affect FL.

The orange wire goes on the top of the motor and the gray on the bottom.  Be careful and quickly solder the wires to the round motor connections.  Don't use any more heat than necessary.  Make sure you don't leave any sharp points on the solder.   If soldering is not your area of expertise, rather than use too much heat, remove sharp points by sanding.

Rap the back of the motor with one or preferably two layers of electrical tape to ensure the connections don't short to the split weights.  If you do find that you have a short after you finish the locomotive and don't see any obvious reasons for it, I would start looking here.

I didn't find a great way to route the chuff sensor wire.  I had to blacken it with a marker as it would otherwise be plainly visible.  It does work well without a problem when installed per their supplied directions.  So go for it!

Putting you locomotive back together:

Before putting your locomotive back together, make sure the gears, especially the one that will be sandwiched in the middle of the split weights, is clean and free of fuzz.   A strand of fuzz seemed to be the culprit in my locomotive not running well after I was done.  I didn't have any fun putting this locomotive back together the first time and wasn't looking forward to doing it twice!

To find out for sure if you wired the motor correctly, you will have assemble the locomotive.  Hopefully, you will have less trouble than I did.  Six or more hands are desirable!  Reinstall the plastic nuts.  Snap on the spacer rings.   With any luck, they will stay put.  You will likely have to push up on the nut when trying to get the screw to catch.  Sometimes I found the screw was attempting to go between the nut and the weight; not through the center of the nut as intended.   Spacers may unsnap.  You will have to slide them back in the partially assembled locomotive.

Don't forget the two white blocks that go between the weights and hold the screws for the underbody.  Keep checking on these before you tighten the screws securing the weights as these two blocks will keep shifting out of position.

I sandwiched the flickering firebox lights between the weights and the plastic underbody.  The slot for the trailing truck lets the light out.

Here's a list of the screws and where they go:
Long black: rear underbody
Long silver: front
2 short black: underbody
Short silver: right side weight, rear

Getting the body shell back on was difficult.  I tried taping the excess bulb wiring to the inside of the shell.  Other excess wiring was taped down to the firebox area of the split weights. Persevere, you will get it on!

Now enjoy your great sounding locomotive!

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.

CV: Value: Description/Details:
Short Address - Have them program this.
Brake. If you are used to momentum, leave this 0 until you are.
Set this CV before, CV 18 and CV 29.  This along with CV18 will set the long address to 4449.
Set CV17 before setting this CV.  This along with CV17 will set the long address to 4449.  WHEN DONE, set CV 29.
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 controls firebox.
F2 Whistle.
F3 Bell.
F4  Blow down.
F5 Mars light.
F6 Dynamo.
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
 0Ah  F1 flickering firebox and  F5 Mars light.
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.  Fireman Fred is not used with 4449, an oil burning model.
  1xh Pneumatic grease gun.
  2xh Boiler pop off.
  4xh to use auto blowdown.  I use F4.
  8xh Enable selected background effects.
Foreground Effects.   1110 Dual air pump, cam chuff sync, DDE, two cylinders.
  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.  Not used when cam chuff sync is used.
00h-3Fh Exhaust tone control.
00h-FFh non-DDE exhaust volume control.

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