Disassembly, Tracing Wire, and Decoder "Plugging"

My Bachmann Light Mountain (standing in for a New Haven class R-1), had been having intermittent trouble lately (it'd randomly decide not to move, despite the sound working) and I suspected the decoder to be the source of the trouble. This engine came "DCC-ready" way back in 2003 and was the first engine I ever converted, using a Soundtraxx "drop-in" decoder/speaker combo intended for a Bachmann 2-8-0 (so it was my first sound install as well).

While it's been serving me well these past 14 years, the sound was starting to sound dated - and the motor control problem was the final straw. I also wanted to try  Loksound's new Full Throttle steam sound so, having a Loksound decoder on-hand (and an  iPhone speaker), I figured it'd be a good time to attempt a conversion.

If you'd told me a year ago that I'd not only be able to disassemble a steam loco, but I'd be willing to remove & replace all of its electronics, I'd have called you crazy. But after attempting  a few projects which others thought crazy, this didn't end up being all that intimidating. You just have to be methodical, take your time, be patient - and keep good notes!

Notes re wire routing/colors on the PCB in the engine and the PCB in the tender, as well as the NMRA standard. (so you don't get lost,  click here for an exploded diagram - and if the worst happens,  click here for spare parts) coffee stain unnecessary

 

Begin by disconnecting the engine from the tender (being careful of the wiring harness/plugs), and remove the tender body shell (remove one screw and lift like a clam shell). To remove the boiler, first remove the front and rear trucks for access. There's a screw holding the smokebox to the cylinder yoke, and a screw toward the rear of the engine holding the back end.

 

From left to right: screw to remove drawbar to get it out of the way, screw holding the rear together, screw holding the trailing truck, screw holding the pilot truck, and screw holding the front together. NO NEED to remove the other screws - doing so would allow all the drivers to come out, which you don't want.

(you can always click on the image for a larger view)

 

Once those are removed, the boiler comes off. I then removed the old SoundTraxx decoder. Thus:

Tender on left, shell in background, old decoder and boiler on/in foam cradle, chassis in front.

Note worm gear which engages the main bull gear on the 2nd set of drivers.

These wires come from wipers on the left and right side driving wheels.

Part of the note-taking process involved physically marking the sockets with what wires go to them. In the photo above, I've unattached the small PCB at the back of the frame to 1) allow me to better see where the wires go, and 2) to make it easier to mark up. "T" is for track, "L" is for light, and "M" is for motor (left and right - I marked the "T" socket on the side for left and right as well).

Once I knew where all the wires on the engine side were coming from, it was time to figure out where they went in the tender. This is the PCB in the tender:
 

What's wrong in this picture?

Note all the extraneous stuff (capacitors & snubbers & such) that Bachmann added to comply with world-wide electronics standards. You don't need any of that stuff in the US (and maybe Canada?). I'd be getting rid of this board since I planned to hardwire a new socket, but first I needed to trace all the wires as I did on the engine.

Removing the two tiny silver screws allowed me to remove the board to get at all the wire tracings.

Pfffft!

And - inexplicably - I discovered that Bachmann had reversed the colors of the track/wheel wires coming from the engine (right side) and the ones coming from the tender wheels(!). I made special note of that fact.

From  Lionel Strang's excellent  DCC book)

For a plug, I used one of the plugs I'd snipped off of one of the Loksound decoders which I  hardwired into my FAs.

Snipped Loksound plug on the left, with tiny wire pigtails; on the right is the socket I plan to use (those pins are what you solder the wires to)

Starting the delicate process of soldering decoder wires to the tiny pigtails on the plug.

The good news is that the snipped plugs had these little pigtails of wire to solder to. The bad news is that those pigtails were REALLY tiny! It's delicate, close work, but remember to add heat shrink tubing to the decoder wire before soldering it to the pigtail, use a little flux, tin both wires, twist together, then touch with the iron. Finally, slide the shrink tube over the joint to insulate it and apply heat to shrink it in place.

And here's the NCE decoder all "plugged."  Hindsight being 20/20, next time I'll cut the wires all to similar length first so I don't get a kink caused by the shortest wire like you see above.

And that's where things stand at this point. The next step will be to "socket" the wiring harness that I cut off the old tender PCB. Once that's done, I can plug the NCE/test decoder in and confirm proper operation. Then I'll know for sure that the more-expensive Loksound decoder will work and I won't let the smoke out.

If you have any tips/suggestions/guidance, please be sure to chime in. In the meantime, stay tuned for more DCC adventures!

"Sock(et)ing" a Harness, Orientation Failure, and Final Install

As I mentioned last time, the next step on this decoder install is to add a socket to the wiring harness which I removed from the PCB in the tender.

It would have been great to not have to add a socket - and I suppose I could have just hardwired the decoder directly to the harness - but it's not as difficult to do as I thought it would be. And it allows me to test my install with an old decoder which is easily removable.

As with soldering wires to the plug, just remember to add heat shrink tubing to the wires beforehand, strip & flux the wire and tin the wire and pin. Bend a little hook in the wire, wrap around the pin, touch with the iron, and slide the tubing down to cover the connection.

Remember to solder the track pickup wires from the engine and tender together first before solering to the pin on the socket. And you'll need a larger bit of heat shrink tube. Yeah - I'd forgotten ALL of that and had to redo it.

VERY IMPORTANT: As with the plug, be sure and solder the correct wires to the correct pins. Unfortunately, you cannot rely on the wire colors on the Bachmann harness - you'll have to refer to your notes about what each wire does and attach it to the correct pin.

And above is the finished socket on the harness on the right, with the decoder plug on the left. The two "stray" wires (black & red) going off-photo to the right will be attached to the tender truck track pickups.

And here's everything reconnected in the tender: track pickup wires connected to the tender trucks, 8-pin socket, and wiring harness with the socket on one end and the engine-tender connectors on the other end.

So far so good . . .

I then plugged in the NCE/test decoder, powered up my  NCE Powercab, cycled through the menus to activate the Programming Track, put the engine on the test track, then connected the alligator clips to the track. I figured this'd be the safest way to proceed.

Then I went to read the decoder - "No Decoder Found" was on the readout. No problem - I'd just turn the plug around. Then the readout said "Short Circuit Detected".

Whaaaaat??!!

I double checked that everything was wired properly. And it was - kinda. By that I mean that the wires on the plug were perfect (it helped that the wire colors were NMRA standard and I had another decoder to use as a guide). And it looked like the socket was wired correctly - then I realized I'd made a mistake:

The diagram I was following showed the wire configuration viewed from the socket side; I'd soldered my wires to the pins - and did them in the same configuration, but on what would be the underside of the socket. Yup - I'd manage to spend an entire evening soldering tiny wires to tiny pins and did them in mirror-image away from where they were supposed to be.

ARGH!!!!

At first I thought I'd have to undo all my work - cut off all the shrink tubing, unsolder all the tiny wires, and reconnect everything the right way. But then - in keeping with the spirit of the season - 

I'd just saw the plug in half and reverse the sides!

Yup - that's what I did. And yes, it was a little tedious, and I had to use a very thin-bladed razor saw, and I had to be careful not to nick the tubing or wires. But I did it - and I'd like to think it took far less time than undoing/redoing everything. At least that's what I choose to believe.

I plugged in the test decoder again, put the engine on the programming track, and - Christmas Miracle of Miracles - it worked!

So, knowing that I had a working install, I next put a new Loksound Select decoder in my decoder tester, fired up the Lokprogrammer software, and loaded the  Soo Line Mikado Full Throttle steam sound package onto it while I finished working on the engine.

Primarily, all that entailed was cleaning out some excess grease around the bull gear on the 3rd set of drivers, making sure that the chassis/running gear would roll freely without any binding, and putting the engine itself back together (I wouldn't be able to reassemble the tender until the decoder was installed).

While I had everything apart though, I explored different locations for the speaker. I ended up putting it in the tender has I'd originally planned, but as you can see above, it might be possible in this engine to cut down an iPhone speaker to fit in the weight above the drivers where the lighting currently is. It'd take some fussing, but it's probably doable. I took the photo above for reference since I may try this in the future.

But for now, I wanted to keep things simple & clean. So I used some Kapton tape to secure the wires in the engine and reassembled it.

The Loksound decoder was all ready by this time and all I did to it programming-wise was to change the address to the engine number (3304). I figured I'd play with the unmodified file for a while before decided whether/how I wanted to program it further.

So "all" that was left to do was to install the decoder and speaker in the tender. This ended up being more difficult than I'd expected, since there's a huge mounting post right in the middle toward the front that you have to work around.

But as you can see above, I finally got a configuration that would work. The socket/plug are on the floor at the back of the tender, the decoder is on top of them, and the speaker is tucked in to the side of the mounting post, secured to the tender shell with a piece of double-sided foam tape. More Kapton tape makes everything nice and tidy.

Final Verdict

The engine sounds great, with the iPhone speaker providing plenty of volume. And of course the motor control is superb, which is typical for Loksound decoders. But I think I still have a lot of work left to do on the programming. Of course, the chuffs will have to be synchronized to the drivers, but many of the volume levels on the different sounds aren't what I'm used to hearing (having actually been lucky enough to work on a few 1:1 scale steamers). And I want to move the functions around to match the configurations I have on my other Loksound-equipped engines.

But all in all, I'm certainly on my way. And no matter what changes I have to make, using a Loksound decoder means I won't have to open this engine up again if I don't want to - I can make all the changes (and even upgrades) right on the programming track.

(Heh - I guess the only reason I'll have to get back in there is if that funky socket I rigged decides to malfunction at some point. But I'll take my chances.)

With my first "real" steam locomotive DCC install now behind me, I have to admit I'm not quite ready to tackle another one yet. I want the lessons I've learned on this to sink in a bit more. And of course I have plenty of other projects to do.

Hopefully though, sharing my experience here will give you some tips and/or insight - or at the very least, warn you about a few things NOT to do! As always, you can leave feedback in the comments - I'd especially like to hear how you would have done this differently (heh - other than "buy a ready made socket & plug!") and I'm always interested in any tips/guidance or suggestions you have.

In the meantime, here's hoping you and yours are having a wonderful holiday season!

Thank you

An informative (and entertaining) install. The best way to learn how to do something is to make a mistake and fix it. Luckily no magic smoke was released. I am doing an ESU install on a Bachmann 2-8-0. The non standard colours are very aggravating. I'll post my method when I ever get the boiler detailing done. 

Question

Would it unbalance the engine to cut off the front of the weight, or mill it to locate a sugar cube speaker there? Is that giving away too much weight? It would put the sound under the stack and above the cylinders, where it should be.

Thank you and Question

Thanks Greg! I'm glad you thought it was entertaining - which I did too, after the initial shock %^)  I'd be very interested in seeing your install.

And thanks Graham Line for the question - short answer is that I'm not sure. I actually don't think it'd be necessary to mill out the weight any more, since there's already a space there. But I think you may be asking more about whether to mill the weight where it's underneath the stack and above the cylinders. Again, I'm not sure how much would have to be removed and what difference that might make to running characteristics. But I may try it sometime.... :^)

What was the overall problem?

Did you figure out what was causing the Soundtraxx decoder to have a problem? If it was an LC or a 1st generation Soundtraxx, I understand. It is probably about as good as the old MRC sound decoder I currently have in a Bachmann light mountain.

I am curious because I am having similar problems with the decoder. It will act like it is getting hot and in about 5 minutes or less, the sound will quit and the motor control is all but gone.

I am just curious if the problem lies with that ridiculous belt drive that Bachmann designed or if the decoders from long ago just were really junk?

Actually not sure

The Soundtraxx was/is the first gen drop in, so it's likely the culprit. But yeah that belt drive leaves a lot to be desired. I'll definitely keep y'all posted as I figure out what the problem definitely is. 

Interesting Documentation with Photos

Very interesting install with documentation photos. I'm sure I will return to this discussion when I get to the point of opening up my many locos for inspection, upgrading, fooling around with DCC/Sound install,  etc.
Thanks

Interesting your experimentation with sugar-cube speaker(s). I ran across a fellow's claim that these are now the only type he will install. I think I will post a new subject thread on that subject. (and I will provide a link when I get that done)

Thanks, Chris for sharing

Thanks, Chris for sharing this install on your Bachmann engine. I appreciate your methodical and interesting way along with photos of explaining how you did it. Your humor is also a bonus .

I have five,Bachmann  2-8-0s, a few purchased on line with early DCC/Sound installed. Although, I find the sound capability good for these early DCC installations but they probably "pale" in comparison with newer decoders. However, I have yet to have replace the belt for the drive on any of them (I do have a spare) due to slippage/breaking and the oldest is over twenty years old. They just seem to keep rolling along smooth and reliable. For the price they are good value.

BTW, since I model IC and this 2-8-0, is based on an IC prototype I suggested to Bachmann that when/if they produce a "sound/value" edition of this locomotive they include a tender backup light and footboards since this engine was used primarily in local service. They thought that would be a good addition.

Barry

Thanks Brian & Barry!

Thanks for your comment Brian - I hope you'll let me/us know when you start doing your installs. And do be sure to share that link to the new subject thread when you start it.

And always great to hear from you Barry - glad you enjoyed the post (and the laugh at my expense :^) I'll be very interested in knowing how your Bachmann steamers continue to perform. A lot of these are getting pretty long in the tooth and I'm curious as to how well that belt drive is going to age or if it's going to turn out to be trouble...

New Subject Thread Link

Here is that new subject thread link I promised,...

Sound & Sugar-cube Speakers
https://forum.mrhmag.com/post/sound-sugarcube-speakers-12208699

...doesn't appear to have attracted replies?

DCC Installs---

I've run a business of installing decoders & sound from my home, since 2006. Some of you may have even sent models to me for sound, or decoder installation? In all the years since 2006, I've seen the wrong color wire used in many Bachmann (My friends & I call them "Botch-man") locomotives.

I've even joked that "Sum Ting Wong say, we out of red wire today, we use yellow"! I've had 2 of the same engines apart, say a 4-6-0, or a 2-8-4, and neither one of them will have the same color wires for the headlight, motor, etc. 

One time in my beginning years of DCC, I plugged a sound decoder into my Bachmann C&O 4-8-2 Heavy Mountain, with No Problems! The next one I bought, I did the same thing, plugged it into the NMRA 8-Pin socket, placed it on the track, applied power & "Poof"! Smoked rolled out the tender, and the decoder burnt up in a heartbeat!

Upon further examination of what caused it, I found that the track wires (which are normally wired through the 2-pin plug), were run through the 4-pin plug, and the motor wires connected through the 2-pin plug! With jumpers installed, this ran fine on DC when tested, but we all know the motor brush wires have to be isolated from the track pick-ups on DCC! 

Now, when I install a sound decoder in a Bachmann Steam loco, 99% of the installs I remove the DC board, and make sure where the wires are coming from, then hard-wire the decoder wires directly to the tenders plug connections! Check your work with a volt-ohm meter, and use a 9V Battery with test leads to find the headlight & motor wires coming from the connector on the locomotive! You'll save yourself a lot of grief!

Joe Bliss

Allegheny Model RR Services

8 Pin Plug Question

What tool did you use to strip the short pigtails on the 8 pin plug?  My wire stripper will interfere with the adjacent wires when I twist the tool to strip the insulation from the wire stubs.

Wire Stripping 8 pin socket

What tool did you use to strip the short pigtails on the 8 pin socket?  My wire stripper would have interfered with the existing wire pigtails when I tried to twist the tool to cut the insulation to expose the wire.