Help needed on HP 7900A disk drive (mechanical)

I'm in need of sage advice from others on the list, due to my lack of troubleshooting/repair experience with large (14") hard drives. I'm a sophomore with electronics, but these beasties are largely mechanical and out of my meager knowledge set. Background: I finally got a brand new (yes, really brand new) blank disk cartridge for my HP 7900A disk drive. The drive has never been powered up since I got it. The spindle motor won't even start on these drives unless the cartridge is in place (there is also a fixed platter underneath). Since the drive is obviously not checked out, I wanted to get blank media to test so I didn't ruin valuable data on a cartridge I am getting later. First I very thoroughly cleaned the drive inside and out, cleaned all contacts, heads, positioner reticule, etc. etc. etc. I then checked the power supply out carefully. Then I powered up the drive (without the cartridge) and tested a number of the basic mechanical functions, interlocks, and test points on some of the cards called out by the operating manual. Then I wanted to try loading the cartridge to see if the heads would crash nicely :) Keep in mind that once the cartridge is in, there is a load switch that powers up the spindle and 30 seconds later the heads do a seek. At any time during the spin up or seek, the unload switch will immediately and very quickly retract the heads and then the drive spins down. "Problem": I put the cartridge in the drive and hit load. You can hear the spindle come up to speed. Exactly 30 seconds later as stated in the operators guide, you can hear the heads move and then the drive ready light comes on. From what I understand if there are any problems at all up to this point, the drive fault lite would come on (including a seek fail, etc.). I kept my finger on the unload switch. The second the heads came out I could hear a disconcerting noise. I immediately hit unload. I removed the cartridge, and inspected both the cartridge and heads carefully. No obvious signs of problems. I reloaded the cartridge. This time, when drive ready lit up, the drive was nice and quiet for about 25 seconds. Then I started hearing the noise again. On and off, more and more, so I hit unload. Rechecked the heads and cartridge again - no obvious signs of damage. Tried loading the cartridge again. This time it ran for a few minutes before I heard the noise. I unloaded and rechecked everything, still no signs of problems. Gee - can you tell I'm paranoid about possibly ruining the new cartridge and/or the heads? :) The sound is not quite metallic, but very close. It sounds like something rubbing at high speed but at a pretty high pitch. The best way I can describe it is that it is almost identical to the sound an 8" floppy disk makes when you put it into an RX02 drive and close the door (the media turning inside the sleeve), but much louder. I'm pretty uncomfortable proceding with diagnostics, etc. unless someone here can calm my fears as to what the sound might be. Is it just due to the fact that it's a brand new cartridge, or is it indicative of a potential head crash, just a belt issue, dust, etc? I'm pretty familiar with the whine a drive makes when the bearings are going out, and it does not sound like that sound. Any help, ideas, thoughts, etc. are MOST appreciated! Jay West