Alfa Romeo Repair: Starting problem, check voltage, battery connection

Question
I have an 88 Graduate. Recently, the battery died.  I jumped the car only to have the battery die a few days later.  Then I replaced the battery with a new one.  The car started fine and ran w/o problems for a couple days.  After not driving it for 1 week, I noticed that the car would not start and all electical systems were out (horn, clock, etc.).  Something drained the battery - no lights were left on.  After putting the new battery on a slow charge (it came back to fully charged) and reinstalling it in the car - the same symptoms resurfaced.  No power anywhere in the vehicle.  Any suggestions?  Thanks.

Answer
Classic symptoms of an alternator not charging the system.

Charge the battery. then start engine and check voltage at battey with engine runningd.  Any reading below 12.67 volts means alternator not working.  Next check for voltage at alternator battery connection.  Next check for voltage at field connection.  Then check for volt drop between engine block and negative lead at the battery.  Now change the alternator.