NEC Drive Problem (CP/M System)

Ok, I have a puzzle that I need help on. I have an NEC Dual 8" Drive System. This is a CP/M system. But my drive #2 has a problem. Drive #1 works fine. Symptoms: Can't boot from drive #2 Can't read files from drive #2 Can't write files to drive #2 CAN get a directory listing from drive #2 CAN write to FAT, as when trying to copy files If I try to load files from drive #2, I get a failure with the following error: "Bdos Err On B: Bad Sector" If I try to write files to drive #2, the directory entry is written (except that it is TEST.$$$ instead of the correct extension). But the data for the file is apparently NOT written. I get the same error. I see attempts to read and write but these always end with the error above. It looks like the write head must be good, as a filename is saved to disk. It looks like the read head must be good, as the directory can be listed. Any suggestions as to what could be causing this? Could it have something with head movement? Perhaps the directory storage is on a track (sector) that can be reached and the others can't? I'm stumped. Note: I have not actually looked inside to see if the head is moving properly (that may be next but I know it does move some.) but I have reattached all the connectors to the drive and controller. SECOND QUESTION: The drive is an FD1165-A. I can't locate such a drive. But I have located an FD1165-FQ. I wonder how compatible the FQ version is with the A version. Can parts be exchanged?