Cadillac Repair: charging system, cadillac fleetwood brougham, 1989 cadillac fleetwood

Question
I have a 1989 Cadillac Fleetwood Brougham 87,000 original miles,5.0 engine.the car when purchased was fine;everything worked;the only thing wrong was that you could hear the AC compressor running even when the AC was off.Anyway, the car was stitting in the yard idling and the lights went dim;didnt pay much attention to it at the time.turned the car off came back 1-2 hrs later the car wouldnt start.got a jump and it started,let it run to charge up for maybe 45minutes moved it in the yard cut it off DEAD.was told that the starter could be at fault,so i changed the starter.nothing still died.Then changed the battery to optima red top.It started up went to work the next day,stopped to store to eat,came out it started,went to work,got off work at 6pm dead,had to get a jump drove home approx 8miles home on jump.so now changed alternator everything seemed to be ok.checked the voltage at the alternator had 14.5 volts.drove home started car again started right up.came home from work next day started car cranked right up with a few pats of the accelerator.then i start to hear this loud hum in the radio (when car was going dead would always hear loud hum in radio or when i press on brakes) so i knew something was wrong.cut car off and it wont start.replaced all the parts is there something i missed or did i burn up the alternator that quick.the check engine light is on also.

Answer
Something is drawing an excessive amount of amperage from the battery when the car engine is shut off as if parked for the night.

What you need to do is charge the battery and drive it to any auto parts store such as AUTOZONE and they will test your charging system for battery condition, Alternator performance and the amperage draw of the battery. The normal amperage draw of the battery when it sets overnight is 1/2 amp.

Until we know what condition the above are in, We cannot do any diagnostics.