Hi Guys
There has been much written about alternators recently
Whenever I get problems I take the alternator off the car and drop it into my local auto-electrical Mr Fixit and they usually manage to fix it on the bench. Very often it's a case of replacing diodes or rectifiers, although on one occasion they changed the field winding, replacing the damaged winding with one I got from a scrap yard. This from a similar sized, same make alternator with different end plates.
They have a really ancient machine for testing alternators, it looks like something out of a Frankenstein movie but does the biz
The last one they did for me was off a Toyota Hilux, a very expensive part to buy new because there is a vacuum pump on the back for the brake servo system
Anyway check it out use your fingers to walk thro' the yellow pages and good luck
Jenksman