Percussive maintenance sometimes works but with disk drives I would first remove it and twist it quickly a few times to cause inertia to move the disk platter. That twist has worked for me in some cases.
Good point.
Percussive Maintenance....Heh heh.
Wally Shirra, on Apollo 7, used the more common terminology. His control panel lights were "actin' funny". He told mission control that every thing was honky dory when he applied some brogan maintenance!