This installation is for a HO Scale Bachmann SD40-2 using a TCS WOW121 Diesel Decoder, AK-MB1 Motherboard with built in Keep Alive®. Shown prior to installation.
To start off this install, first remove the couplers and their housings. Then we must first remove the two screws located under the tank and then the tank cover. Save these screws for re-installation.
Next, remove the two screws on the bottom of the frame on either side of the speaker. Tank care with the loose speaker to not damage it. With these screws removed, while gently pulling outwards at each end and along each side of the frame, lift the shell off of the frame. Take care to release the handrails as you lift off the shell so they don't break. Save these screws for re-installation.
The Bachmann SD40-2 shown with the shell off. Remove the two screws and the wires from the original lighting board and remove it from the chassis. Save one of the screws for reuse. Trim, tin or lengthen the wire leads as needed and using small lengths of TCS 3/32" and 3/64" shrink tubing, insulate these solder leads.
With the board removed, remove the two screws holding the weight onto the chassis and lift the weight from the chassis. Set the front LED platform aside for re-installation.
On top of the moor is a cap and two resistors. Clip and discard these components as they are not necessary in this installation.
A view showing these components.
With the pieces removed, prepare the motor and solder new wire leads to it.
A view from the right side of the chassis showing the bottom motor lead installed.
A view of the top motor lead installed.
Using Kapton or another insulating tape, isolate the bottom of the motherboard from the chassis.
Using one of the saved screws, mount the AK-MB1 to the chassis as shown.
Solder the track, motor and speaker leads to the motherboard according to the included wiring diagram.
Using a small amount of hot melt glue, reattach the original front LED platform onto the chassis in its original position.
Replace the rear LED into it's original holder and solder the the front and rear LED wire leads to the motherboard. TCS motherboards include on board current limit resistors for LED use. There is no need to apply external resistors for LED use.
You can now plug in your WOW121 decoder.
Lastly, in order to keep the wires neat and prevent possible shorts, lace the wires into a bundle using lacing cord, which is a wax impregnated string
used for wire bundling and making harnesses. There are many choices of lacing cord available from Digikey www.digikey.com. We use part number 802534B BK032-ND
Now you can close up the locomotive and reinstall the tank and coupler assemblies. Be sure to be mindful of wire routing and reassembly of the shell as to not damage
or foul the installation. Your Bachmann SD40-2 is now WOWSound equipped and ready to roll!
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