7900A drive: 1 , Me - 0

Here's another installment in the ongoing HP7900A drive saga (yes, it's a plea for advice and/or sympathy <grin>) Installed new (refurbed) lower heads and new lower platter. Recleaned inside of drive. Powered up, put in new removable cartridge. Hit load switch and waited 25 seconds, then hit unload. Did this a few times (the blowers and drive spins up, but the heads don't load for 30 seconds - did this to get any remaining particles out). Removed cartridge, powered down, removed covers and reinspected everything inside. All looked well (including heads, which were fully retracted). So, this time I powered up and hit load. Waited 30 seconds, heard the heads move out to cylinder 0. Ran drive like this for about 3 minutes, no problem. Hit unload. When I removed the removable cartridge, I noticed the heads weren't quite retracted all the way. They were well off the media, but not all the way back home (the heads weren't touching each other, but they were close). Manually pushed the heads back, rechecked everything I could find. Repowered up the drive, after 30 seconds the heads loaded. Drive ready lite comes on and ran for about 15 minutes. No HDI sounds at all. I was elated. Hit unload, and after about 20 seconds heard very soft HDI. This time I left the cartridge in, powered everything off, removed the covers, and this time the heads weren't retracted at all. They were sitting right on the media. Strange thing is, there's no marks on the media, the lower heads I replaced look pristine, and the upper heads have only the very slightest indication of oxide. Gee - perhaps this is why the drive originally had a head crash before I got it? I've been through the "theory of operation" text and flowcharts. Several things confuse me. First, I thought that hitting the unload switch was pretty much of an immediate voice coil retraction - I didn't think this went through all the normal logic circuits. Second, the coil can't be completely shot I wouldn't think, because as I understand it the drive ready light won't even come on unless the positioner moves out to cyl 0 correctly. Before I replaced the heads and media, I don't THINK I had this problem, I think I would have noticed if the heads weren't retracting before. But, I can't imagine that anything I did related to replacing the lower head set and the lower platter would have anything to do with this. Input anyone????? TIA! Jay West