This installation is for a HO-Scale Walthers EMD SD70 ACE using a TCS WOW121-Diesel Decoder, AS-MB2 NC Motherboard and KA3 Keep Alive®.

This was performed by our friends from DCC Xpress installations.
They offer high quality WOWSound installations for a flat rate complete with free return shipping!
You can find them at:

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

HO-Scale Walthers EMD SD70 ACE shown prior to installation.


To start off this install, we must first remove the front and rear coupler screws and their housings.
With the couplers removed, there are also several screws to remove including two located at each end as highlighted above in red and another two found on either side
in the middle as shown below.


With these all 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.

The Walthers EMD SD70 ACE shown with the shell off. Remove the 3 screws highlighted above in red along with the wires from the original lighting board
and remove it from the chassis.

With the original lighting board removed, trim, tin or lengthen the wires as necessary. In order to allow space for the AS-MB2 NC, the rear screw
post needs to be trimmed flush with a file or clippers.

Using double sided foam tape, attach the AS-MB2 NC to the frame as shown above and solder the motor and track pickup wires according to the included wiring diagram.

As this locomotive has a speaker pre-installed into the frame, solder the existing speaker wire leads to the motherboard as shown above.

Likewise, solder the existing LED lighting wire leads to the AS-MB2 NC according to the included wiring diagram. In this installation, the front and rear headlights were soldered
to the front and rear LED pads. The ditch lights were soldered separately to the #1 and # 2 pads located on the rear of the motherboard.

TCS motherboards include on board current limit resistors for LED use. There is no need to apply external resistors for LED use. 

Using the same double sided foam tape, secure the KA3 to the frame as shown above and solder the leads to the AS-MB2 NC.
You can now plug in your WOW121 decoder.

Now you can close up the locomotive and reinstall the shell 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 Walthers EMD SD70 ACE is now WOWSound equipped and ready to roll!

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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