This installation is for a HO-Scale Athearn Genesis GP40-2 using a TCS WOW121-Diesel Decoder and GEN-MB1. This install was performed 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

HO-Scale Athearn Genesis GP40-2 prior to WOW121-Diesel Decoder, GEN-MB1, and GEN-SH1 installation.


To start off this install, we must first remove the front and rear couplers and their housings. Once that is complete, the shell will lift off of the chassis.

Do this by holding the fuel tank with one hand and lifting the shell off by pressing up underneath the end platforms with your other hand.

With the shell off, we can now remove the factory light board. First remove all the black wire clips and disconnect the wires from the board.

All the wires have been unclipped prior to taking the above photo. Once the wires are loose the factory light board will then easily unclip from the motor mount.

Since we're installing sound in this locomotive, we need to remove the speaker housing weight. The two screws need to be removed to do so.

With everything removed, we can now install the GEN-MB1 and solder our pick-up and motor wire leads.

Next, secure the ? speaker and 35x16mm speaker with the two screws from the weight removed earlier.

Next, solder the speaker leads to the GEN-MB1.

To secure and seal the screw holes on the speaker, some hot glue will work well if the fit is loose.

Lastly, we need to attach our headlight leads to the front and rear headlight pads on the GEN-MB1, and plug-in the WOW121-Diesel decoder.

For the installers convenience, the forward and reverse headlight pads are already setup for 1.5v bulbs that Athearn models use.

If you require a 12v supply, please follow the GEN-MB1's instruction manual on how to do so.

NOTE: We have found that using lacing cord is an excellent solution to taming "wild wires". Using lacing cord is a important step to neatly bundle and dress the wires which are prone to being pinched or cut by the shell (during closure) or tangled by the drive train. This simple addition makes a tremendous difference in keeping your installations neat and preventing accidental shorts from damaged wires.
Lacing cord is a wax impregnated string used for wire bundling and making harnesses.
There are many choices of lacing cord available from Digikey We use part number 802534B BK032-ND

With all three main components mounted, we can now close up the locomotive and reinstall the coupler assemblies.

Make sure to position the lighting wires so as to avoid moving parts and the cone of the speaker when placing the shell back on the chassis.

You have now installed a TCS WOW121-Diesel Decoder, GEN-MB1, and ? speakerinto your HO-Scale Athearn Genesis GP40-2.

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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