Just restarted my MX5 after a period of inactivity. Engine fires, runs for a couple of seconds before belt starts squealing, few seconds more - much smoke. Open bonnet, broken belt. Cannot turn alternator by hand. Remove broken belt and put socket and breaker bar on alternator. After about 5 deg of movement ( hardly any effort ) alternator frees and can now easily be turned by hand but with a slight tight spot. What has happened? Is the alternator knackered? I have got a new belt to fit but if the alternator is on its last legs I would rather fix it now than be stranded by the roadside. Advice please.
PS alternator is 60k miles/13 years old.

I think I would bung it in for an exchange unit. It has done it's work and not worth a breakdown which could cost you much more.

there were a couple of different alternators fitted,wrong one wont work so make sure you get it right first time

could be a couple of things, for instance it may be:
a small stone being ingested,
or the baring failing.

maybe other causes too.

best bet is to replace it, because
a) it may have caused damage
b) you will always worry about it
consider yourself lucky, they usually wait for the worst possible moment to fail. (much like computers!)