new alternator troubles

Greetings Friends,

I just installed a new 75 amp alternator into my 89 f150, I6 4.9L 300. I believe
it had a 60 amp in prior. however the guy at the parts store said it should be fine.

After putting it in I tried to start it, I needed to have it jump started because the battery was drained. (left my phone charger on). The truck turned over then it went completely dead, no dash lights, nothing. The jumper cables were warm to the touch. What do you think could have happened? i never have had any problems like this until now.. please help!!!
thanks