Gilbert American Flyer steam engines are great subjects for converting to DCC with sound. Common ones are readily available at train shows at reasonable prices. They look good, and with the addition of a can motor and DCC, they run and sound as good as anything available in any scale!
This article describes a conversion of a 312 Pacific using an SnS can motor and a SoundTraxx Tsunami decoder. There are multiple ways to do this, and I continue to modify my process as I do new conversions. But this method works, and works well. Here is a video of the completed project.
Currently this is not a step-by-step how-to article, because I didn't take enough photos. But the procedure isn't too complicated, if I missed something please send me a note.
Start by separating the tender from the loco. I like to rewire the loco first, so take off the shell. This unit didn't have the original 4 pin plug with it. If it did, I would use it. In this case I'll use a small Miniatronics 4 pin cable. Remove the original AF motor, label it and put in in safe storage for the future. A nice feature of this conversion is the loco can always be put back into original configuration if desired. Install the SnS motor being careful to follow the orientation written on the mount. This is a 2 screw installation. Don't worry about wiring it yet.
This locomotive will use a SoundTraxx Tsunami sound decoder to control the motor and generate the sound. The headlight bulb will be replaced by a 5mm Golden White LED, and it will also be controlled by the Tsunami. The smoke unit requires too much current to control directly, so the Tsunami will control a small relay which will control the smoke unit..
The Tsunami decoder has a wire for chuff syncronization. Since the smoke is what you really want to sync with the chuff from the decoder, we need a sensor tied to the smoke unit. There are several ways to do that, my choice in this conversion was to use a magnetic (reed) switch and a magnet. To mount the switch as well as the decoder, I built a little platform of balsa. It is glued to the chassis straddling the connecting rod for the smoke piston. The Miniatronics magnetic switch is gluded into the corner as shown in the photo. The magnet is glued to the connecting rod, you can see it better in the next picture.
I mounted the components, then wired them together. In this picture you can see the Tsunami decoder mounted on the balsa shelf. The SnS motor has also been installed. The capacitor which comes with the Tsunami is glued to a convenient spot on the chassis to keep it out of the way. You can just see the end if the magnetic switch sticking out from the top corner of the balsa shelf. The magnet which actuates it is glued to the connecting rod of the smoke piston.
Here's the wiring:
The pickups and the speaker are in the tender. This means we'll need 4 wires connecting the loco and the tender, 2 speaker and 2 track power (from the pickups). If the standard AF 4 position cable/connector are in good shape you can use it. In this case I used a 4 wire cable/connector from Miniatronics. I number the pins left to right, 1 to 4. Use the 2 outer pins (1 and 4) for track power, the two inner (2 and 3) for the speaker.
This side shows the relay which is used to control the lights and smoke unit.It is glued onto the side of the balsa platform. I use a 12V, 1A relay from Radio Shack. Note the piece of cork used to close the slot on the smoke unit. This decreases the mechanical chuff so it won't compete with the electronic one.
Here's the other side, fully wired. The 4 pin cable/connector is held to the top of the motor with electrical tape for neatness, its not required. The wires sticking out the front are for the headlight. They terminate in a 2 pin socket made from a pb board header. The leads of the LED plug right in. You could also use a 2 pin cable/connector from Miniatronics, or just solder them directly to the LED leads.
Here is the boiler front with the LED installed. I used a 5mm Golden White LED, turned down a bit to fit. I put shrinkwrap over the leads to avoid a short. Next time I plan to try a 3mm LED. It will fit easier, and I think it will look just as good.
That completes the locomotive wiring. I usually wait until I can test it with the tender brefore reassembling.
After removing the mechanical reverse unit and wiring and storing them for the future, test fit the speaker, mark where it will be on the tender floor, and drill some holes to let the sound out. I used a SoundTraxx oval speaker.
Glue the speaker to the floor using Goop or rubber cement. Wire pin 1 of the cable to the left side pickup, and pin 4 to the right side. Connect the 2 middle wires to the speaker.
Plug the tender and locomotive together, and put it on the programming track. If you can successfully program, you probably don't have any shorts, so its a good test before trying it on the mainline. Program the address at this time. Also, set CV 112 to 128, which turns on cam chuff sync.
That's it! The Tsunami defaults will be for a directional headlight, and the smoke will be on F5. Have fun!