[cctalk] Shugart 850/851 repair needed

Hi folks -- long time no post. I'm wondering if there's anyone who would be interested in trying to fix my Shugart 850/851 8-inch floppy drive. It was new old stock when I bought it, and hasn't been used much, but last time I tried it, it would no longer read any data from the back of a floppy, only from the front. I use it with a Catweasel and my cw2dmk software, so I was able to try a few experiments from the software side. What I see is just plain noise coming out on the data line when reading the back. It's possible of course that some unobtainium chip has gone bad, so I don't expect much. But it would be nice if someone with more electronics skill than me, and more knowledge about these drives in particular, would be willing to take a look at it. The drive is of course big and tough to ship, so it probably only makes sense for someone within driving distance (I can drive it over or you can come by), which means being in the SF Bay area. I live in Palo Alto right near downtown. FWIW, the drive and a power supply are mounted in a case that I made by ripping the guts out of a surplus desktop PC case. The power supply seems fine and the drive can read the front of disks fine. Thanks for any help, Tim