5400 SCSI

[Franklinstein]

The SCSI bus on my Performa 5420 seems to have died. No drives work, internal or external, in any configuration, regardless of the OS.

The same drives work fine on any other computer.

Nothing seems charred or otherwise destroyed on the logic board, so I'm kind of at a loss as to why it suddenly decided to crap out.

Anybody have any suggestions as to where I should start looking for the problem? I haven't seen anything clearly marked as a fuse anywhere on there...

 

[equill]

Only in one machine out of eighty-odd that I have worked on have I been forced to conclude that the SCSI controller chip had died, but it does happen. If there is no other SCSI bus in the Mac, as is the case in the 5400, the inescapable consequence is that you must replace the MLB.

But first try a (grounded) one-inch bristle paintbrush to clean around and between the pins of the relevant controller, and follow that with canned air cleaning. See whether there are tell-tale goops around the pins from a burst/leaked capacitor. You can swab that off with a cotton bud/cotton tip and clean water containing a little vinegar, if it is limited in area, being especially careful to free the pins of the controller chip from (green) corrosion. Then use clean water to rinse. Allow time to dry—from a day to several days depending on your geographic situation—before firing up the MLB again.

If the above is successful, know also that, ultimately, the cure will have to include replacement of the capacitor.

de