Mogul DCC installation



Bachmann 2-6-0 Mogul

DCC installation by Udo Hoffman


Mr Udo Hoffman has done quite a writeup on this loco, and there's not a lot out there on the net. So, he has graciously allowed me to publish his information on converting a Mogul to DCC. Udo will respond to questions if you have any: This email address is being protected from spambots. You need JavaScript enabled to view it.

This article describes the disassembly and installation of a DCC decoder in the Mogul. It's also a great reference on just how to tear the unit down.


Preface by the author:


I have been in the "business" of Model railroading long time in Germany, with a lot of long breaks in between.

As a boy I started with TT gauge (ROKAL) and later, with own children I changed to LGB.

Then there was a long break.

My job brought me to China and some years ago, I found in Shanghai a starter set "Big Hauler" Circus train from Bachmann…. Then the "problem" began…

My wife helped me a lot and even gave me locos as a present for birthday etc.

So, I started to collect Bachmann locos, but not Big Haulers…

I prefered the Spectrum 1:20.3 line.

On my roster meanwhile are a lot of locos and rolling stock.

As I am an engineer, not only let the trains run is what I like, but also improving the stuff.

So I started to install DCC Decoders (ESU) in all my locos.

Meanwhile I met a nice guy from Germany, who told me a lot about the American Narrow Gauge Railways.

He was also the guy, who changed my habit of doing improvements.

Earlyer I mostly made that changes without any documentation.

But he has a lot of the same locos like me and also wanted to improve his stock.

So, he asked me for some hints… by memory it was very difficult….

Even when I today want to disassemble some older loco which I changed already some time ago, my memory is leaving me alone….

So, many many thanks for the "mental support" of Dr. Peter Wiegner from Vallendar Germany!!



  • This article describes the installation of an ESU Loksound XL, but you can of course use any DCC sound decoder (e.g. Massoth, Zimo etc.) You will need to adapt to the specifics according to the decoder, but the job should be simplified with the help of the file "Mogul electric”. (I will add a link to the document here)
  • ESU has the suitable sound files for the mogul to download on their web site.
  • This article can be used for the Spectrum "American” 4-4-0 too, it's even less complex, since there is only the firebox flicker to deal with as an "extra".


Chapter 1:  Removal of the Boiler / Cab


For a  "simple" decoder installation, this is not necessary.  See the chapter "Decoder Installation".

For the work, I prefer to use the original styrofoam box for handling the loco to avoid damage.

Put the loco in the lower part of that box and disassemble the boiler supports and the lubrication pipes at the loco front.



Removed parts:



Then cover the loco with the top of the box and turn it around to remove the bottom part of the box, so the chassis accessable.

To remove the front truck, remove the screw at the pivot point, the far left in this picture.


With the truck removed, you can now see the cover plate between the cylinders, held with two screws.


Remove the screws and the cover plate. The screw under the smoke box (front support of boiler) is now visible, remove it.


Next you need to find 7 more screws which hold the chassis to the boiler shell.

4 of them are in the firebox sides (two each side) just under the running board.


Fireman’s side:

Engineer side:


Here you see also the connection rod from the Johnson Bar to the valve gear.

Some detail:


This tiny screw has to be removed also. This is the "1/2". Don’t loose it !!

To get access to these bolts, esp. the rear  ones, you should remove the small air tanks. Each is fixed with two screws to the running board.

Here you see the tank removed:


Look at the tiny pin in the pipe connection to the brake cylinder.

Just swivel the tank a little and it will go out. The tank and pipe are of metal.


After you have done this all, we have to look for another two bolts.

They are hidden behind the rear drive wheels

Engineer side at the position of about 10:30 a.m.

Fireman side at the position of about  1:30 p.m.



Here the picture of the Engineer side:



As you can see, I did not maintain my own recommendation… I did not put the loco in the box and let the bolts fly around!

But, anyhow, you can see where the screw driver is attached.

To get access to these bolts, you must remove the gear box cover first (8 screws), so you can lift the driver a little.

Recommendation: After removing the bolts behind the wheels, just fix the cover again. 4 screws are enough for temporary fixing.

That avoids anything falling out, when you have to turn the loco.


When this work is finished, you should be able to lift the chassis from the boiler.

Do this carefully. The support assembly fort he cab on the back will fall out and you have to disconnect the motor wires (white plug under the firebox) and fiddle out the chuff connection for the tender from the frame.


Now, you have access to the connection board just under the firebox and to whatever you need there.

In the Chapter "Decoder Installation", you will find more pictures from the Chassis etc.



view of the disassembly:

During reassembly, take care that the sandpipes are in the correct position!



Chapter 2: Removal of the Cab


I did this work, because I wanted to add some cab light to the loco…. I love lights!

To do this, you must do all the disassembly in Chapter 1, otherwise you will not get out the rear two screws which hold the cab.


Additionaly, during the first step of chapter 1 (loco on the wheels in the box), you must remove the cab supports, and most of the piping on the boiler….


The compressor can be removed by carefully putting a screw driver behind it.

Take care not to damage the paint. The compressor and pipes are made of metal.

Remove the pipes as well as the compressor:

In the above picture, you also see the handle for the sanding control on the top of the loco.

To take this out generates a problem. The wire is glued into a small hole in a plastic lever at the sand dome.

Take the lever with a plier and the wire itself with another one. Then carefully wind the wire out of the lever.


The picture below shows the handle installed, just under the handrail:


You also should remove the safety valve from the steam dome:


This comes out easily, just lift the unit up.


Turn the loco upside down. Under the cab are four bolts to hold it.

In the picture above, the engineer's side, you can see one bolt on the left, just above that drain, and one on the right, just beside the pipe.


Below is a detail of the rear screw on the engineer's side:



The one at the rear end is in this picture half covered by the support bracket at the end of the loco.

This one is the reason, why you must remove the boiler……

The other one is "free".

If you want to remove the cab, it will be also better to remove the roof first.

It is fixed with two tiny screws just under the roof at the backside.

The front side is just "clipped in".

Carefully lift the backside after removal of the bolts, so it will pop off.


What you can do now is shown in this picture:

And… you can add some light! See the following chapter!



Some additional remarks: It may be necessary to remove the big air tank also, if so, first remove the pipe behind it (one bolt) and then the tank itself (2 bolts). All the parts are metal.




Chapter 3: Adding Cab Light


Addina a light for the platform, up underneath the roof:


Light in the cab, suspended on wired traversing the cab:

Wiring at the back head which will supply power:

I used two 5mm warm white LEDs, "short form" (about half the length of the normal ones). The connections inside the cab are made from "magnet" wire (coated for insulation).

Two holes drilled in the top of the back head, just behind the valve block.

Additionallym,  I glued a small plastic bracket inside the cabin just at the front wall with two holes in it, this is to guide the wires.

As you see (hopefully) in the picture, I also painted the transparent plastic besides the windows brown (TAMIYA XF-68 / Nato Brown).

Also the back side and the sides of the LEDs are painted brown.

The rest of the wiring is shown under "Decoder Installation".




Chapter 4: Decoder Installation

For the Decoder installation, I will describe the following alternatives: (all with the goal to not add additional cables to the tender.)


First: "quick and clean improved"

  • This is the complete installation with:
  • Decoder in the boiler        
  • Chuff Trigger directly connected to the decoder
  • Speaker in the tender
    Additional second speaker in the boiler (option)
  • Additional Cab Light
  • working smoke unit
    needs to dismantle boiler from chassis !!
  • only one cable (4 pole) to tender


Second: "quick and clean simple" 1

  • This is the installation with:
  • Decoder in the boiler
  • Chuff trigger via tender
  • No dismantling of boiler / Chassis !!
  • No smoke unit
  • Speaker in the boiler
  • Two cables to tender (4 pole + 2 pole)


Third: "quick and clean simple" 2

  • This ist the installation with:
  • Decoder in the boiler
  • Chuff trigger via decoder
  • No dismantling of boiler / Chassis !!
  • Speaker in the tender
  • No smoke unit
  • Only one cable connected to tender (4 pole) second cable (2 pole) can be removed


The decoder I used was an ESU LOKSOUND XL 3.5


What shall be connected to the decoder?



Simple 1

Simple 2

Front Light




Cab Light




Firebox Flicker yellow LED




Firebox Flicker red LED




Ashpan yellow LED




Ashpan red LED




Speaker Boiler




Speaker Tender




Chuff Trigger




Steam Unit








Track Power





The decoder has 8 auxiliary outputs and inputs for the trigger, so there are plenty of connections for any option.

The separate outputs for the LEDs in the Firebox and Ashpan gives the possibility to "play" with these lights (Flicker / Strob / Blink / Dimmer etc)  to "tune" the flicker appearance.


For the electrical details please refer to the attached file "Mogul electric".

Now, we come to the "mechanical part" of the installation:


There is an existing set  of chuff contacts, see below:

You can see the two brass plates in the middle of the rear drive shaft.

The horizontal wires on the shaft work like a switch. There are four of this around the shaft (0° / 90° / 180° / 270°). That means 4 times per revolution, the "switch" will be closed by the wires, so 4 chuffs per revolution.

Below is a picture of the underside of the chassis with gear box cover open:

On the right side you can see the two brass tabs of the chuff contacts. The wires go to the 2 pin  socket above and to the right of the driver.

Disassembling the unit this far gives the ability to remove the sound surpressors on the end of the motor.

Just lift the motor / gear unit upwards out of the chassis to access it. You can unsolder the PCB and connect the wires direct to the motor.

Take care that no wires are damaged, especially the ones near the valve gear.

Here's a picture of the "top side" of the chassis:

To the left of the motor, just on top of the middle drive wheel, you see the plug for the motor connection.

The black wires on the far right go the to 2 pin socket for the chuff contacts.

If you want to connect the chuff direct to the decoder, you must reroute the wires.

Just a simple way:

Open the screw on the board with the two brass latches in the middle, putt he chuff wires under that, so the plug will be in the area of the motor plug and fix the board again. So 50% of the chuff connection is done!

The brown plug on the right side is the connection, for the ashpan flicker, normally plugged in the board under the boiler…. See the picture below:


Above shows the board under the boiler in original condition. Here you can see the white plug left side for the motor connection.

The brown plug right side is for the firebox flicker.

This will be plugged in the board in one of the two plugs. The second one is for the ashpan. See also the picture above.

Now we come to the changes:

Note: in the picture above, the plug for the firebox is plugged in.

On the left side of the board, I have connected all the red cables together (4 pcs).

They are the plus poles of the LEDs in the ashpan and the firebox.

The black ones I have made new / longer with different colors (see file "Mogul electric" page 1  "color after rework" in "Main PCB (in boiler)").

The blue cable on he top ist he plus pole fort he cab light.

The purple one is the minus pole.

I have connected / reduced all plus poles to one cable going in the boiler to minimize the number of cables to be "pushed" together later.

I have also wrapped them together with shrink tubing (you may use small cable ties also).

Here an overview of the boiler / cab from the underside:

You can see the cable coming out at the front of the boiler.

First leave them long. You can cut them later.

If you don’t want to remove the boiler from the chassis and need no cab light, omit these steps.

The original cables are long enough, but only red and black color….

You also see two white plugs, hanging left top of the PCB. This is motor and chuff.

Don’t mix them up!!!



Lets have a look inside the smoke box:

In the middle on the top is the smoke unit. It is mounted on a "PCB mounting plate". The PCB mounting plate is held in the smoke box with the two screws you see at the bottom.

Behind the front plate of the PCB mounting plate, just under the smoke unit you can see the edge of the main PCB.

All the cables are just "stuffed in" There is the danger of wires touching the hot smoke unit. This will be noted in reassembly.

Now remove the bracket by removing the 2 screws:

Remove both of the screws and carefully draw out the PCB mounting plate.

Be sure to look inside, and see that the top of the PCB does not hang up on any wires as you withdraw it. The picture below show the PCB withdrawn. You can see all the wires around it:

The switches from the smoke box front  have already been removed in the above picture.

After this, I first put the electrics for test on my bench….

The reason for that was to find out what and how it is connected.

The results are in the file "Mogul electric", page 1.

Especially I wanted to know the connections for the red and black cables on the right side of the main PCB.

With the information you will be able to connect all the LEDs correct to the decoder.

I also checked the connections to the front light.

Bachmann has a 680 Ohm resistor in the minus line to the Front Light LED.

I checked the brightness with 16V DC and found it OK.

It is not so bright as most LEDs,  it appears that Bachmann has set this up to handle higher track voltages, so I decided not to add an additional resistor.

The other LEDs (Firebox and Ashpan) I supply via a resistor of 1 K ohm in the minus line just at the point of connecting to the decoder.

This has an advantage in that the resistors have solid leads, the advantage will be shown later.


Next, remove the PCB and the smoke unit from the PCB mounting plate. The PCB has two screws, the smoke unit another two.

Now, take a look at the "PCB mounting plate" and find out how to mount the decoder:

The two mounting posts, which supported the PCB, are already removed.

I made some U-shaped profiles from 2mm styrene. The height is about 6mm and the width on the top about 8mm. The length is the same as the width of the decoder.

First glue the left side piece at the end of the PCB mounting plate, than use the decoder as template and glue the right side one.

Next, drill some holes just besides the right side support through the base of the PCB mounting plate (see picture) and two holes in the left side support (horizontal) for a cable tie (see picture).

The purpose of the cable tie is to hold the cables which will be run from the right side of the decoder through the holes then under the PCB mounting plate to the left side and fixed in upward direction by the strap.

This will make inserting the assembly into the boiler much easier.

Now we can put the decoder on the PCB mounting plate:

Be sure to remove the red jumper (back side), because the ESU speaker has 32 Ohm.

To remove the jumper, just cut the clear shrink tube in the area around it, it won't affect the warranty.


Before we go on, there is some preparation in the smoke box necessary.

If you want the trigger connected to the decoder directly, you should make the cable longer. Just solder one connection plug (female) to one end of a 2 pole cable.

I used thin black wire, then route it in the boiler, with the connection close to the connection board under the fire box.

Then you must make a cable for the motor connection also.

But this is nearly ready. Just cut the cable with the connector from the polarity switch.

Then prepare the polarity switch according to the plan in the attached file.

Connect it to the programming plug and assemble it to the smoke box head cover.

The cables which go from the switch to the boiler are the rail connections, which come from the connecting board under the fire box.

The red one to the right and the black to the left will be connected to "Track" on the decoder.

The programming plug is glued in. Take care to glue on 3 sides only. On the top is the guide fort he mail plug! No glue! If you don’t want the switch and plug, just connect the rail cables directly to the decoder.

Now prepare the wires in the smoke box:

The picture above shows the work in progress.

The purple wire (cab light) gets a 2 K ohm resistor (to keep it not too bright)

The red one is U+, no resistor.

The others are for the LEDs in the fire box and the ashpan, 1 K ohm each.

Note: If you do it the "simple" way, "no removal of the boiler", you will have 4 red ones and 4 black ones. Just put the red ones together (U+), add one resistor (1 K Ohm) to each black one and just connect to the decoder, later with the mapping of the decoder, you can find out which cable, resp. which function output is connected to which LED.

In the picture above everything is ready for connecting to the decoder.

By the way, you should mark the cables during assembly, especially the motor and the track connections. They have the same colors!  Don’t mix them up!

The long yellow one is the minus pole of the front light. The plus pole is the single black one left side, connected to the red U+ already.

OK, now the decoder:

Here you can see the wires from the right side of the decoder (motor / track / speaker / chuff / U+) are routed through the holes in the PCB mounting plate to the back side and there secured with the strap.

The cables from the left side are bent upwards, this will help the cables to "fold" inside the boiler.

When assembled, there is about 25mm of space between the weight in the boiler and the back side of the PCB mounting plate.

You also can see that there is space for a speaker in front of the decoder.

The speaker would have to be angled towards the decoder.

If you don’t use smoke, you can just cut the bracket for the smoke unit, to give even more space in front of the PCB mounting plate.


Note: The Bachmann polarity switch is a 2 pole double throw switch, so it will connect the decoder to either the programming plug or to the track.

The reason I did this is to eliminate any bad / dirty connection from the rails to the decoder during programming. I often had this problem with my Bachmann locos.

OK, now just carefully feed the decoder assembly into the boiler.

In the slot in the bottom are only 4 wires: 2 from the track pickups, and the wires back from the switch to the decoder. Easy to handle and the wires will not have any chance to contact to the smoke unit.

Some pictures with the programming connection:

Arrangement for programming

For programming, I use the ESU Lokprogrammer, just left of the glass. Finally I could enjoy the glass of red wine!


Some additional remarks:

After finishing the Mogul, I installed the decoder the same way in my Spectrum 4-4-0 (American).

Some additional problems came up. The reason was that earlier I had already installed a decoder (in the tender) and "gutted” the boiler.

Therefore I had to reinforce the PCB mounting plate. I did this by adding a plastic board under the PCB mounting plate.

This has the disadvantage of facing problems during assembly into the boiler.

So I made the wiring a little different. I think, the following pictures are "self explaining”. Now all the wires are in the gap below the decoder.

Wiring alternative:



Chapter 5: the Tender

Stock, the tender only serves as additional power pickup.

There are 2 connections (wires from the loco) to the tender.

One 4-pin connector and one 2-pin connector.

The 4 pin cable has two wires used for the track power, the other 2 are free.

The 2 pole connection shall give the chuff signal to the tender, not further wired.

To open the tender just remove two screws in the front area under the frame:

They are just under the first wheels of the front truck, both sides.

On the back side there are just snapping latches at the body.

After removing the screws just lift the body in the front and take it off.

Now the frame looks like this:

The big ESU speaker for Loksound XL (dia 78mm) fits with some small modifications in the provided place, just grind a little around the frame and remove the four small supports.

The speaker housing (ESU) is a little high for the tender, so trim it down about 5mm.

Now glue the speaker in place.Just some glue around the metal ring of the speaker.

Solder the wires to the speaker and drill two holes for them in the housing.

Now mount the speaker housing on the speaker.


I always use white wood glue to fix the housings and seal it.

Now you route the speaker cables to the PCB under the frame.

Now, we come to the PCB. Just in the front middle under the frame.

Only two wires are connected.

The two free ones of the 4-pole plug we will use for the speaker connection to the decoder in the loco (see also attached file).

If you don’t install the speaker in the tender (but in the loco) and you want to use the chuff connection without having the work to disassemble the boiler from the chassis.

You just "route" the chuff through the tender.

That means just connect (bridge) the two free poles of the 4-pole plug to the two of the two pole plug.

Then you use the two free cables of the 4-pole cable in the loco for the chuff.


Below shows the the version with speaker in the tender.

Some additional notes on the installation of the speaker:

You can use a 3 inch diameter (76,2mm) speaker, it will fit in the provided place without any trouble.

You only should remove the four small supports, so the speaker sits smooth on the frame with his outer ring.

Also you may not install the speaker housing. It is up to you, many people have good results with the sound also without a housing like this.


After Assembly and carefully checking the electric, everything should work.


One last hint for "easy cabling":

All the "coded" cables on page 1 of the file "Mogul electric" have to be cut / unscrewed from the PCB ( the PCB will not be used later). Be sure to mark each of the wires before disconnection, so later there will be no confusion on which wire is which.






Weather Underground PWS KCACARLS78