Looks like LEDs to me. I suspect your problem is either the pickup wire (which you checked) or the wire coming from the wiper on the axle for the common. If it's not that you have a board issue on the LED circuits.
A more important question is where is the power feed to those boards from the trucks? Up the end of the car?
The arrow point to the LEDs there is another opposite side of each board for a total of 4. The circuit boards are highlighted.