Replaced Alt.twice still running off battery still not chage

'98 S-10, 2.2, Stick, 120k. Alternator died so I replaced it once. still no charge to the battery. took it in to the shop they said i got a bad alternator from the car parts place. went a got a better end alternator and still no charge to the battery. I check connections from alternator and battery and checked for any blown fuses. Help me.