Only think to remember about all Amiga PSUs is that they are all now getting old, with some reach 20 years old. So they are all at the age that their capacitors are starting to beak down and they will fail.
Good luck finding an original one. Failing that there are PC PSUs that should fit inside an A3000 case. You could even look at the mini-itx based PSUs if you can't find any small enough for standard PC cases.