These alternators are usually fairly reliable unless water gets in. Before you go shipping it off for an expensive rewind, check for broken wires where they come through the case and for poor connections to main harness/rectifier under seat. The yellow, blue and brown output wires are the ones you need to look at, earth is via black/white wire and connects direct to battery.
The solid black and white wires connect the points to the coils and are not part of the charging circuits.
Might be easier to buy a good used alternator. Should be plenty out there. Brian.