This installation documentation is for the HO-Scale MTH 4-6-6-4 Challenger. This installation uses a TCS WOW121-Steam Decoder and an AS-MB2-NC Motherboard with included KA3 Keep Alive®.
This installation also uses a TCS 6-pin Mini Connector to connect the locomotive to the tender.
NOTE: The speakers in the tender must be wired in SERIES to avoid damage to the decoder's audio amplifier. DO NOT wire the speaker in PARALLEL. If you are not familiar with what that means, CLICK HERE to read an article all about it.
Note that MTH locomotives make use of a "Common Cathode" electrical design, whereas DCC decoders are "Common Anode." This means ALL of the LED lighting functions on the model will be in the opposite polarity from what a decoder needs. You either need to cut certain traces on the PCB's, or reverse the physical LED's in the model in order for the lights to function. Alternatively, you can remove all of the original lighting boards and replace them with your own LED's.
The MTH 4-6-6-4 Challenger shown with the shell on.
To start this install, first, slide the pilot truck to the side and remove the two screws located on either side of the locomotive, the right side one is shown highlighted above in red.
Next, slide the rear truck aside and remove the two screws underneath the rear of the locomotive, the right side one is shown above highlighted above in red.
Shown with the shell removed, remove the screws on the lighting board and clip the wire leads to the lighting board and smoke unit.
Note: Take note of the wiring order from this original board before removing it so you can be sure to splice the wiring harness correctly. The smoke unit will not be used in this installation and these wire leads can be left in place.
With the boards removed, lengthen or shorten the wire leads, trim and tinning as necessary.
Spice in the wiring harness to the track, motor and headlight, feeding it back through the rear of the locomotive.
With the locomotive properly wired, lace the wires into a bundle with waxed lacing cord and reassemble the shell onto the chassis in reverse order, being sure to route the wires carefully to avoid potential shorts. The locomotive is still complete.
With the locomotive complete, turn your attention to the tender. To remove the shell, remove these two screws highlighted above in red.
Next, also remove these two screws highlighted above in red at the front of the tender. The tender shell will lift off of the chassis.
Inside the tender shell, remove the lighting board shown above.
Underneath this board is this platform. Remove the screws shown above in red and remove this plastic shroud.
Then clip the wire leads from inside the tender shell and remove the lighting board highlighted above in red.
Remove all the components on the tender chassis and trim and tin the wires as needed.
Using foam, double sided tape, mount the AS-MB2 NC motherboard and KA3 Keep Alive to the tender chassis as shown.
Solder the track and KA3 wire leads to the motherboard. In this installation, the original speakers were used, wiring them in parallel.
Splice in the other end of the wire harness from the locomotive and solder the wire leads to the motherboard.
You can now plug in your WOW121 decoder. Secure the wires with small pieces of Kapton tape. Lastly, in order to keep the wires neat and prevent possible shorts, lace the wires into a bundle using lacing cord. Now you can close up the tender. Be sure to be mindful of wire routing and reassembly of the shell as to not damage or foul the installation. Your MTH 4-6-6-4 Challenger 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 then a 1/64 of an inch. When the wire gets tinned with solder, the insulation will shrink back more. Try to not expose any more wire then 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