Classic/Antique Car Repair: car not keeping charge, altanator, volt meter

Question
I replace battery and voltage regulator, took off hot on batt while running after jump off and car still runs. car won't start again after cutting off. what should i check now. should i still get my alternator checked anyways. thanks

Answer
Anthony;
       Hi - I thought I sent you a reply a day or 2 ago.
I would get a volt meter and check the output when it is running - see what the altanator is putting out .if no good replace it.  ok / you might have run the battery down when you took the cabel off.