Athearn SD40-2 Decoder Installation featuring the RTR-MB1 Motherboard with Keep-Alive™, WOW121-Diesel Decoder by TCS

Important Soldering Tip:
Please do not use any flux either liquid or paste on the mother board. It will damage it. Use only Rosin core solder approved for electronics use.
We recommend to use only Kester "44" rosin core, SN63PB37, .015" diameter, part number 24-6337-0007.
This can be ordered from Techni-Tool under Techni-Tool part number 488SO157

The Athearn SD40-2 prior to installation

First, remove the coupler box screws and the coupler boxes from both ends of the locomotive.
Gently grasp the shell on both sides, spreading the shell while lifting to remove it.


The Athearn SD40-2 with the shell removed. In this installation as all the original connections are direct to the frame,
it needs to be converted into wiring to be able to install the RTR-MB1 motherboard.

Using needlenose pliers, carefully open the tabs securing the front light bracket and remove it from the frame.

The Aethearn SD40-2 with the front light removed.

Next, unclip the elecrical connection and using a blunt end probe or file, push on the tabs underneath the frame to release the motor from its mounts.

The Athearn SD40-2 with the motor removed.

Pull outward as shown in red on the metal clip and remove. Be careful removing this phosphor bronze strip as it is holding in the motor spring which tends to launch when you remove this contact strip.

After bending the small tabs in the opposite direction on the clip, solder a motor wire to the underside as shown.

To ensure proper insulation, cover this metal strip with Kapton tape.

Shown with the mounts reinstalled.

Place a strip of Kapton tape down the center of the frame where the motor will sit. It is critical that there is good insulation here becasue a short between the motor and frame will destroy your decoder.

Next, tin the top of the steel strip mounted to each truck.

Clip the RTR-MB1 motherboard to the top of the motor and solder the RED track connections to the trucks, and the BLACK track pickups to the front lighting bracket (with the bulb removed)

Next, with the 25 x 14mm speaker wired and inserted into the UNIV-SH4-C enclosure and mount this assembly into the top of the shell using hot glue or double sided, foam tape. Solder this and the lighting wires onto the motherboard as per you installation diagram.

In this installation, we added a 1/4w 1k ohm resistor.

To ensure a neat and clean installation, prevent pinched wires, and avoid potential shorts during reassembly and operation, lace the wires in to a bundle.
Reattach the shell and couplers and Your WOWSound equipped engine is now ready to run!

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

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