Charging Issues

I have a 1976 Datsun 710, runs great (120+ Compression on all 4 cylinders) however I have had some minor electrical problems. I got a new Alternator, Battery, Starter and Voltage regulator, everything seems to run and charge fine for 10-15 minutes then the alternator seems to drop and it goes running off the battery. The battery was dead, I am charging it overnight to see if that is the problem. If this doesn't help anyone have any ideas? Also have replaced the battery cables and terminals and I do not see any fried or shorted out wires.....

Mac

i just joined the forum today so if you fixed the problem ignore me. I have one question about how you tested the alternator's charge to know it was charging for the first 10-15 mins. It sounds like a parasitic draw problem if you ask me. reply if you still need help