studio 440 "proprietary" floppy drive

[Rob]

I need a floppy drive primer here... And, yes, I know that this may be a
moot point due to the fact that i will be getting the scsi update and be
able to use my zip drive shortly, but it still bothers me that the
floppy doesn work.

Ok, first question, how does the drive signal to the processor that a
disk is present? I had always though it worked on a beam being broken.
The controller is a WDC1770..

Another thing is, if the floppy IS broken, how hard is it to repair? 
I have had some advise against this, but if the floppy is proprietary,
how else do you make it work?

Given that the WDC1770 controller is fairly standard, what would
preclude me from just hooking up another drive? If i were to know the
pinouts of the drive, why couldnt I just  hook up an ordinary drive? 

Its like saying that a screwdriver will work here, but if its over there
it wont.

Hopefully I just have a few bad ROMs (those little window EEPROMs go bad
once in a while and the programming degenerates). Then I wont have to do
any of this