This installation is for a HO Scale Athearn F7A Early frame.
With milling of the frame, they have been able to utilize a RTR-MB1 motherboard, WOW121 diesel decoder and UNIV-SH4C WOWSound kit.
HO-Scale Athearn F7A Early frame shown prior to installation.
To start off this install, you must first gently pulling outwards along each side of the frame and lift the shell off of the frame.
Take care to clear the front coupler as you lift off the shell so it dosen't break.
The Athearn F7A Early frame shown with the shell off. Remove the screw highlighted above in red on either side from the weight and remove it from the chassis.
Save these screws for later use. To allow a space for the motherboard and decoder, the frame must be milled as shown below to keep all the components inside the original top of the weight.
With the top weight removed, the frame shown pre and post milling.
Remove the original track pick up bars along with the front light assembly to prep the locomotive for the new motherboard.
Remove the four screws located on the bottom of the frame and carefully remove the motor.
Remove the motor pickup clip from the bottom of the motor, flatten the two bent out tabs and solder a motor pick up to the 'top' of the clip. Be careful when removing this as there is a small spring located underneath that will be released when you do. With the new motor pickup soldered in place, insulate this connection with a piece of Kapton tape to prevent shorts.
Reinstall this clip and the motor into the frame, reversing the removal instructions.
The RTR-MB1 has a motor pick up clip pre-attatched to the bottom, so mounting it onto the locomotive could not be easier.
With the motor back into place, clip the RTR-MB1 to the motor and solder the motor and track pickup wires according to the included wiring diagram.
Using small lengths of TCS 3/32" and 3/64" shrink tubing, insulate these solder leads if needed.
Solder a new track pick connection point to the original light frame and another to the top of each opposing track pick up.
In this installation, we replaced the original lighting with a LEDs, one for the headlight and a second as a Mars light. Using a small amount of hot melt glue, mount these
LEDs into the front top of the shell as shown above. We chose to isolate the light outputs from each other with a small piece of electrical tape over the Mars light.
We have found that LED light output is brightest when shinning directly into the end of the light tube, but in some circumstances they may be placed along the length
of the tube as well with satisfactory results. In doing so, white light LED output would be least affected, while non white LED output will be more affected by placement.
TCS motherboards include on board current limit resistors for LED use. There is no need to apply external resistors for LED use.
With the 25mm X 14mm WOWSound speaker inserted into the UNI-SH4-C enclosure, mount this assembly to the rear, top of the shell as shown below.
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.
With these componenets in place, solder the wire leads to the motherboard according to the included wiring diagram. When attaching the wires to the pads, it is not necessary to insert the wires through the holes. We recommend attaching the wires flat on top of the solder pads.
The RTR-MB1 and GEN-MB1 have on board 1.5volt power supplies to conveniently power all the original 1.5volt bulbs that come with your Athearn locomotive. The front headlight and rear light pads are configured for 1.5volt use. Additional 1.5volt pads are available for other connections for ditch lights etc. If you prefer to use LED lighting as an option, use the LED solder connection pads. Current limit resistors are built into the board so no external resistor are needed for LED use.
You can now plug in your WOW121 decoder.
The installation shown complete. We placed a small piece of Kapton tape over the installation before replacing the weight, to insulate these two surfaces from potential shorts.
Using care, replace the top weight, routing the wires properly to avoid pinching the wires when doing so. Replace the original weight screws.
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 locomotive. Be sure to be mindful of wire routing and reassembly of the shell as to not damage
or foul the installation. Your Athearn F7A Early frame 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. 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
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
In order to keep the wires neat and prevent possible shorts, we recommend lacing the wires into a bundle using lacing cord. Lacing cord is a wax impregnated string used for wire bundling and making harnesses. There are many choices of lacing cord available from Digikey www.digikey.com.
We use part number 802534B BK032-ND