Cool! It would be interesting to see the underside of it.
OK, there a couple of ways to parse that request, so I'll answer the most literal and show the electronics & wiring under the board. The control PCBs daisy-chain together for different requirements, this one with the main control PCB, two motor/cab-control PCBs, and a small customization PCB for running things like the start gantry and the vibration motors in the controller handsets. All the wiring uses plug-in cables. I have 3 different test tracks on that board, which explains the two sets of holes and track connectors lower down that aren't wired up at the moment.
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