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.
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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.
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