Electrical connections have been made to all the fixed sections of track in basically a tree topology through chocolate blocks, B&Q red&black speaker cable, 5-pin DIN plugs between boards to a chocolate block distribution point under the main board and from there a pair of wires come out to the controller.

(For readers considering DCC: there are still lots of wires under the tracks but they don't come back to the control panel, like many of them would in DC, they just keep on joining together, red to red and black to black, until they reach the "tree trunk" of the final two wires, which connect to the DCC controller.)

While I had everything broken down so I could get at the undersides of the boards I took a photo of one of the track joint ends:

I'm happy to report that when everything was put back together, one dropper re-soldered and a board-to-board connection polarity reversed everything worked fine. Rolling stock still click-clicks reliably over the board joints. The next time I make rail joints between baseboards I'll try to use a thinner cutting disc because I think the gap I have now is too large. The clickety-clicks are a pleasant sound but they are a bit loud. On the plus side I know which of my second-hand rolling stock has plastic wheels now - because it hardly makes a sound!

Next it was time to ditch the Prodigy Express controller (which is simple and reliable but a bit limited), and connect up the PiSprog One. This was very easy to get working from another computer on the network or from a throttle app on a SmartPhone, but it took a lot of fiddling around to get a working display connected directly to it! I wanted to use an old monitor with its DVI input connected to the Pi's HDMI output but it just wouldn't work. After a lot of research and trying all sorts of suggested changes I found that the magic incantation, for me at least, was to set hdmi_group = 2 in config.txt.

So now, at last, I can sit in the operating well and really get to grips with fine tuning the control system.

Next jobs: Understand JMRI better, mount the PiSprog underneath somewhere, set up a roster of locos, fit metal wheels to various items, find out why 4705 keeps jamming up.