I have made good progress on this project.

I wired the chassis back up, initially for a quick test on DC power, which involved tack soldering the feed wires to the brush wires. It ran perfectly, so the next step was to wire in a decoder. I chose a TCS M4 that I happened to have lying around. While I am only using two functions at the moment (for the headlights), it leaves the way open to improving the lighting later with separately worked tail lights or cab lights, if I so choose. One correction from the last post: the PCB I referred to did not, in fact have a resistor; it had two diodes and the actual lighting is provided by incandescent grain of rice bulbs. This meant I could discard the PCB completely from this project and wire the lights directly to the decoder.

The presently unused purple and green wires were left intact and secured out of the way. The blue, yellow and white wires were also tacked temporarily out of the way and the red and black wires were shortened and connected to the track pickups and the orange and grey wires were similarly shortened and connected to the brush feeds. I removed the capacitor at the same time. The decoder was secured to the top of the can motor with a piece of double-sided thick tape that also acts as an insulator. I tested again on the programming track, and it all read properly. Address 9222 was allocated (for 92 022).

A quick track test proved it ran very sweetly indeed. You can also see the shiny bits where I ground the height down a little.

After that test, the lights were wired, noting which way the locomotive had run, so the white wire was connected to the forward bulb and yellow to the rear, with the blue common return connected to both.

Photo with lights on at the forward end:

... and photo with the light off so you can see the wiring a bit better.

The body was clipped back on and it had its first run around the layout, minus couplings.

The lighting is fairly crude and is crying out to be improved ... later! The whole cab is illuminated at the moment when the headlights are turned on, as are the tail lights in white. It works as well as I had hoped, though and that's the main thing.

There are still a few minor things to do. I did fit couplings immediately after the last photo. It could do with some handrails on the ends. The cab interiors need painting, which would also reduce the lighting effect. The body is still sitting about 0.5mm too high on the chassis.

I made a small error with the undergear and stuck one small bit on the wrong side so will fix that later too. I suppose my only other problem with it is that I cannot tell which is the front (for DCC operation purposes)!