There is a diode that gets blown on a lot of A3000's when plugging/unplugging powered external devices. Test/replace it and see if that's it.
also check the diode is good and not shorted. It was installed backward on some a3000 revisions. termination wont work without this diode that supplies +5v term power.
@Huron : A3000 scsi is not fickle, all the problems are known and fixable. In the 20 years i have been messing with Amigas i have proven this to many people who swore they had to do a ritual to sacrafice a chicken and dance on 1 foot while touching the scsi cable to make it work
:roflmao:
