This installation documentation is for the Bachmann Light Mountain 4-8-2. This installation uses the WSK-BAC-1 kit, which includes the WOW121-Steam decoder, B-MB1, and 28mm round speaker. This installation was performed by TCS.
IMPORTANT NOTE: There are multiple variations of this tender in circulation with different configurations of the weight. DCC-ready or DCC-equipped models feature a different tender. See the installation variants of the Bachmann Consolidation 2-8-0 for examples of installations in the different tenders.
First unplug the tender from the locomotive and set the engine aside. Next remove the screw identified below in yellow from the bottom of the tender.
With the tender screw removed you can tip the shell from the front to the back (to slip the rear plastic tabs out) and lift it off the chassis. You should now be presented with something similar to what you see below.
This is as good a time as any to point out that there seems to be no standardization of wire colors in Bachmann steam engines. Do not use the colors of the wires on the original board as your wiring guide. The image below shows the standard wire coloring for DCC installations.
With the wires soldered to the MB1 you can now screw it into place using the original lighting board screws.
Now it's time to move on to the speaker. As you can see highlighted below in blue there is a nice opening up to the coal load where we can route our wires so we will mount the speaker up under the coal. To start we will remove the coal load from the tender by releasing tab identified below in yellow and lifting it from the shell.
Here is the coal load removed from the shell and unmodified.
The first thing we will need to do is drill small holes in the coal to allow the sound to leave the tender. We found that 70+ #68 holes worked best for our 28mm (1.1") speaker. Make sure that the holes you drill are only within the diameter of the speaker you intend to mount because any holes outside the diameter of the speaker will actually reduce the sound produced. The best way to drill these holes is from the top with a pin vise and a very sharp drill bit.
The coal load after we completed drilling the holes.
You can see how without light shining from behind the coal load looks almost untouched.
Now that the coal load is read to receive a speaker it is time to prepare the speaker itself. In this installation, we are using a TCS 28mm (1.1") round speaker which sounds absolutely fantastic. We have attached a male 2-Pin Mini connector to the speaker so we plug the speaker directly into the MB1 (NOTE: you can also solder your speaker to the motherboard. See the image at the bottom of this installation to see an example of a hardwired speaker). Next, into order to keep the cone of the speaker from hitting the surface of the shell/coal load we needed to add some short (1/16" or 1-2mm) standoffs around it's front lip. In the image below you can see that we just carefully applied dots of hot glue to four points on the speaker edge which worked wonderfully. It is important to note that you cannot get any glue on the cone of the speaker or its performance will be significantly reduced.
With the standoffs in place you can place the speaker face down inside the coal load and fill in around the edges with hot glue. It is important to create a seal all the way around the speaker to achieve its highest performance.
You can now replace the shell on the tender, screw it back into place, attach the tender to the locomotive and you are ready to run. As promised above, if you want to hardwire you can solder it to the two pads on the MB1 that are identified by "SPKR". In the image below you can see one such wiring solution.
Important Soldering Tip
Please do not use any flux either liquid or paste on the mother board. Over time, the acidic properties of liquid or paste flux will begin eating away at the fiberglass PCB and will damage it. Use only Rosin-core solder or no-clean flux approved for electronics use.
TCS recommends the use of Kester "44" Sn63 Pb37, .015" diameter Rosin-core solder. Kester part number 24-6337-0007.
You can order this solder from the following retailers:
Digikey - PN:KE1110-ND
Techni-Tool - PN:488SO6775
Other solder tips
When stripping wire, only strip a tiny little bit of the insulation. Strip no more than a 1/32 of an inch. When the wire gets tinned with solder, the insulation will shrink back more. Try to not expose any more wire than half the length of the solder pad at most. In no case should solder or exposed wire wire ever be outside the boundary of the the solder pad you are attaching a wire to.
Click here for important information on properly Stripping and Tinning wire