Blue Comet Railsounds

First off, you need to provide exact part numbers for the motherboard and boards you're going to install.

You can get all the connectors and pins from Digikey for Lionel connectors, they're the JST-EH (2.5mm), JST-PH (2mm) and the JST-ZH (1.5mm).  The mating pins are on the page with the connectors.

I use the Engineer PA-09 crimp tool to put these together.

Mother Board is 6912MB00AB, speaker is 6308401536, volume pot is 6918040T41, and the speed sensor is 6309104166.

All of these were listed under parts for the Giacobini Heavyweight Station Sounds Diner on Lionel's Support web site. I was planning to use a reed switch in lieu of the speed sensor. I have the reed switch, and can easily splice it to the speed sensor cable once I know where it goes.

I use a reed switch, it just goes on two of the sensor pins.  I don't have the wiring for that motherboard, I had one some time back, but I used it.

Doesn't the motherboard have silkscreened legends for the signals at the connectors?

Yes, there are silkscreen markings, I just found my magnifier. I can make out where most of the stuff goes, but I was wondering what the marking for the speed sensor would say. It has stuff like "nsaid" silk screened on the bottom.

Also, the pot has a red, a brown, and a yellow wire. Which is high, which is low, etc.?

Thanks 

The pot connection should be the middle for the wiper, and if you get the other two wrong, the operation will be backwards.  You can just swap the wires to fix that.  The pot is a 10K pot.

The sensor has a common, an input signal, and a power feed, normally 3.3V or 5V.  Depending on the sensor, you either connect the input to the common or the power to trigger it.

I have connected the speaker and pot, but not the motion sensor. When I tried to program it, the number took, as it made the steam let-off sound, but when I moved the switch back to "run" and powered it up, all it did was screech when I selected Aux1 7, or any of the other commands.

I know the boards are in the right places, as the motherboard is silk-screened with their locations.

Well, I now have sound. Apparently it wasn't recognizing it's number, but now it is.