Replace one wire at a time. Take great care not to dislodge rotten wires as they’re extremely fragile and will easily disintergrate or become disconnected and if that happens then you’ll need to begin referring to circuit schematics which will just add to this painstaking task. A little brush, like an artist’s paintbrush is also very useful to sweep away the small fragemnts of jacket sleeving that will constantly drop off the cables as it falls apart. No matter how careful you are these old Binson cables will slowly disintergrate making a mess everywhere. It really is a labour of love to restore one of these machines.
When you have removed one wire, measure it and then cut a new piece of wire to the same length. Strip the ends of the new wire, tin them lightly with solder and then replace it. I worked through methodically replacing the single conductor wiring, starting around the mains transformer and power outlet. then went onto the coax. Heat-shrink sleeving can be used to cover the any ‘live’ mains power connections from the the mains inlet to the on-off switch potentiometer, however I prefer to use the more old-fashioned, ‘Hellerman’ rubber sleeves.
More coming at some point. I just wanted to get as much information online as quickly as possible as this is a tricky job.