HP 9885M troubleshooting tips

Hi all -- Picked up a (mostly) complete HP 9885M (8" floppy drive) set up for my HP 9825 computer. I have the 9885M drive itself, a 98032A interface, and the "Flexible Disk Drive" ROM pak for the 9825. I am unfortunately missing the "9825A Disk System Cartridge" tape (hp p/n 09885-90035). Any ideas if this has been archived anywhere? I haven't found it in my searches. (Not that I currently have any means to get it onto my 9825...) Looks like this is actually required in order to format disks. Sigh... Unfortunately, the drive appears to be failing the built-in diagnostic; there's a single LED that goes on when the test starts and it's supposed to go out within a minute if the diagnostic's passed. The LED on mine just stays on permanently. Unfortunately that's the -only- diagnostic indicator on the unit. I've read through the service manual and unless I'm missing something it doesn't really describe how to go about narrowing down the problem. There's a flowchart that basically says "if the light doesn't go out, it's a problem with the controller in the drive unit" which seems fairly obvious... The service manual mentions a diagnostic on the tape, but I don't have this to aid me. Anyone have any experience with these drives? Any pointers for starting out? (I've checked the obvious things -- the power supply voltages look good, etc). Thanks as always, Josh