Athearn P42 Installation including a WOW121 Diesel deocoder, RTR-MB1 Motherboard with Keep-Alive™, WOW121-Diesel Decoder
and UNIV-SH1-C WOWSpeaker Kit by TCS .

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:

These items are available in the WDK-ATH-5 which was used for this installation.

RTR-MB1 Motherboard with Keep Alive™ WOW121-Diesel Decoder UNIV-SH1-C Speaker Kit
Click here for more information on the WDK-ATH-5 and the rest of the WOWDiesel Kits line.

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 P42shown with the shell on.


First, remove the coupler box screws and the coupler boxes from both ends of the locomotive.
There are 4 metal points from the frame that stick into frame directly behind all 4 ladders which will hold the shell in place.
Use a flat head screwdriver to flex the plastic of the shell away from the metal tabs and lift the shell off.

Shell mounting tabs. Remove the wires from the original lighting board.

Then lift the lighting board up from the front of the engine to remove it.

When we completed this installation we found a short between the motor and frame. These next few steps will address that short and are easiest to perform at this point in the installation.
Please be sure to check with a ohm meter that there are no shorts between the frame and the motor. If you do not do this step you will likely fry the decoder.

First, remove the 4 motor screws from the bottom of the engine

Next, tip the motor to the side to get access to the bottom motor pickup.

This exposed wire from the Athearn factory is a decoder killer and needs to be addressed.

As you can see there is a large section of stripped wire left exposed. This could be corrected with heat shrink tubing or electrical tape. We used electrical tape to provide generous insulation.

Make sure you route the motor wire along the length of the phosphor bronze motor pickup bar and up along the front side of the motor.

With the motor short addressed, tip the motor back into its vertical orientation and screw it back into the frame.

Install the RTR-MB1 into the engine by clipping it to the motor like the original lighting board and solder the motor and track pickups to the motherboard.

Next, wire the RTR-MB1 according to the wiring diagram in the motherboard manual. All the original 1.5volt bulbs supplied with the Athearn loco were used. The white wire solder pad is the forward 1.5v solder pad for the front lights. The yellow wire solder pad is the reverse 1.5v solder pad for the reverse lights. The solder pad marked "1.5V" is the common power source for the bulbs. This motherboard can be configured for LED operation as well, the mother board has built in current limit resistors for LED use. Consult the wiring diagram for LED use.

Solder the two violet wires to your 35mm x 16mm WOWSpeaker, glue the speaker into the UNIV-SH1-C (we used hot glue) speaker housing and mount it under the fan housing at the rear of the engine. NOTE: You must be very careful to avoid getting glue on the speaker cone. Glue on the speaker will ultimately cause it to produce no sound and fail.

If your speaker enclosure installation covers the portholes on the enclosure, we recommend adding new port hole(s) similar to the original porting. Be sure that the new portholes are the same size and amount of the original and are vented freely into the locomotive We have found introducing a port of the correct size greatly increases the volume and sound quality of the installation. Too much or too little porting decreases the sound quality.

Finally, solder the speaker wires to the motherboard.

Shown with all the components installed and soldered. Plug in the WOW121-Diesel decoder, and replace the shell and coupler boxes

Your WOWSound equipped Athearn P42 is now ready to run!

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
We use part number 802534B BK032-ND

Please carefully notice how neatly the purple speaker wires are attached to the mother board in this photo. All wire attachments to the mother board should be done in this manner.

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

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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