This one has me quite puzzled. I have a 5 MB profile that suffered damage during shipping - the case bottom was broken badly but I had no idea if it had caused any harm to the electronics or mechanism. So I obtained a new bottom case, disassembled and cleaned the internals and started to reassemble. Before complete assembly, I checked the drive by powering it on. It seemed to startup just fine, stepping through each track and ending with a steady LED on. Great!
The I reassembled the drive and turned it on again. This time, not good. I could hear the head stepping out to track 0, to the midpoint, and back a couple of times, then parking and settling with the LED off.
So I disassembled the drive again, checked all the connections, and turned it on again. Worked fine - hooray. Reassembled, then test again and no joy! After some trial and error it seems that when the outer screws holding the drive to the case bottom are not in, the drive starts up fine. When the screws are in, it fails. WTH? This is almost 100% repeatable 4 or 5 times (one time after reassembly, the drive turned on ok, but the next time I turned it on it didn't).
Anyone seen anything like this or could hazard some guesses?