FD400 drive troubleshooting

From: rcini at optonline.net> > All:> > As you all know from previous posts, I?m having trouble with the drive> system on my IMSAI. While I wait to receive a memory board and some other> stuff from a friend of mine, Herb Johnson gave me some new energy in looking> at the existing iCOM Frugal Floppy system.> > This system uses Pertec FD400 drives. One works perfectly, the other one> has consistent CRC errors as evidenced by the CRC light on the drive> cabinet, and BDOS errors reported by CP/M. I ensured that the spindle is> engaging the diskette hub, and I also cleaned the heads using a wet cleaning> diskette.> > Is there any common failure mode on this model of drive that I should> start tracking down? I looked over the maintenance procedures for the drive> and many if the tests allude to a diagnostics program that can manually> control the spindle and head stepping. None of the iCOM manuals I have> provide diagnostics code for manually controlling the drives in this manner.> > Before I start coding, does anyone have diagnostics code I can use? I> found some code in the SIGM archive (for the iCOM 3712 controller) but it> doesn?t seem to work properly with this controller.>