25.5x15.5x4.5 mm phew! They're big decoders, aren't they?
Doug is right you may have to cut some metal if you want to fit the decoder in the loco, otherwise you can run four wires under the back edge and into the tender, which is what I did with my J39, it just means they are permanently joined together unless you include a miniature plug.
When you separate the two halves of the split chassis you'll see two springs go "pinggg!" off into the blue. These carry(ied) current from each half of the chassis to each terminal on the motor.
Go find them later: You don't need them any more but it's always nice to have spare springs.
If you're going to put the decoder inside the tender do it now. Drill a hole in the bottom just behind the hook to thread the four wires (red, orange grey black) through.
Get some very small (3mm) heat shrink tubing and slide two short lengths (about 1cm) onto the orange and grey wires of the decoder. Solder these wires to the terminals on the motor, the orange goes to the bottom terminal, the grey goes to the top. Now slide the heat shrink tubing down over the terminals and shrink with a hot air gun (carefully) or hair dryer. Unfortunately there's no way of testing whether the chassis touches the terminals, just make sure you can't see any metal when you've finished shrinking. REassemble the two halves of the chassis making sure that the heat shrink tubing doesn't get too squashed. REassemble the wheels and running gear and replace the bottom plate.
Now find some air inside the shell where you could stand two PCB pins that look like this only smaller:
(I put mine just behind the fire door). Drill two holes slightly smaller than the pins and then tap the pins in with a small hammer (or a
big hammer)
Strip about 1cm of insulation off the red and black wires. Twist the bare red wire and wrap it around the pin in the right half of the chassis. Wrap the black wire around the pin in the left half. Solder.
I drilled two small keyholes in the bottom plate with open ends to thread the wires through but it may be different on the Jubilee. See photos (click to enlarge):
Drag all the extra wire into the tender and tie it up with a piece of wire or slide some bigger (6mm?) tubing over it. Test run the loco before reassembling. You can paint the wires black to make them look better but somehow I've never gotten around to it.
You're done :^)
