Electrical problem please help
 

I fried my main fusable link and sence I replaced it my car wont start. I cranks for a couple of seconds then the link fries again. I thought that my starter was drawing to my amps so I replace it with one I had laying around(that I had tested at a parts shop) but it still is doing the same thing. When its cranking it sound like it turns on and off real fast, Like its getting power in pulse's. If anyone can help please post. Oh and the link will burn up even when the key is in the on position so I cant compression start it.

P.S. First gen