So I swapped the logic board and memory, rom into another se/30 and it boots fine. But the hard drive from the system having problems into the working se/30 system and it hangs at the welcome to mac screen.

So it appears to be the hard drive. But it's weird that it hangs. No system bomb error or anything. And I don't understand why when booting from the OS 7.5 floppy it does the same thing????