I've a ZVX4 interface card for the Apple II. This was produced in San Diego, California by Silicon Valley Associates. It allows the Apple II to interface with an 8-inch floppy disk drive such as those made by Shugart.
Along with this card I have some 8-inch floppy disks that make use of a special version of DOS 3.3. Apparently, the DOS 3.3 on these disks has been patched to support the 2.2MB capacity of the 8-inch disks.
The interface card and the 8-inch disk drive I have were just sitting around for years. I got them from a former Apple II enthusiast. I recently decided to try them out in my Apple IIe Platinum. The interface card is supposed to be used in slot 7 only, so this is where I placed it. I put the DOS 3.3 disk into the 8-inch disk drive and booted ... the interface card's red LED lit up and the computer attempted to boot, but the 8-inch disk drive (both left and right drives) refused to work. It seems that due to age this disk drive unit has failed. 
My goal was to eventually use an Apple IIgs to try and make .DSK disk images of the special 8-inch disk version of DOS 3.3 so that it could be archived for collectors and emulator developers, since when I mentioned this find in the Apple 2 forums back in 1999, no one knew anything about it.
Unfortunately it seems this is impossible now, and I hate to think the disks will one day go bad and there isn't a backup of them anywhere.
I don't know what to do ... is this DOS 3.3 version already preserved and I'm just worrying for nothing? Can someone make any helpful recommendations as to what I can do to preserve this software?
Thanks.
I realize that the cars says to use in Slot 7, but I
believe that is because the normal 5 1/4 drives would
be already in Slot 6. The Apple normally looks to Slot
6 first in the bootup sequence and if no drives are
present then the drive search may fail at this point.
If you are only using the 8 inch
drives without the 5 1/4's, try putting the 8 inch con-
troller card in Slot 6 and see if they boot. It should
not hurt your controller card. I have done this with
other hardware cards and suffered no problems. The worst
that should happen is that, again, the 8 inch drives
will not boot. Let us know the results.
Of course, I tried using the card in slot 6 also. Like I said in my first post, the computer attempted to boot the disk in the 8-inch drive, but the 8-inch drive itself appears to be broken. There's nothing wrong with the Apple II or the interface card that controls the 8-inch drive.
Here's a replacement drive.
Hi,
was the ZVX4 interface card the only interface card that supported 8 inch floppy drive on Apple II, and what was the brand/model for floppy drive itself?
Wbr,
I.
Hello together, in Germany there was the company IBS that manufactured different partialy very advanced Interfaces for the Apple II series.... you should take a look at my own downloadsite
http://www.harrowalsh.de/Elektronik/APPLEBOX/appleboxdownload.htm
at the very bottom where i display different Diskcontrollers.... spot out the IBS AP14 Diskcontroller down there...
It had Schugartbus for 8 Inch, 5,25 Inch and AppleDisk connectors to work with all 3 Standards....
the controllers were sold with Patch- and TestDisks for 3 different Systems ( DOS ( partialy ), UCSD, ProDOS and CPM ).....
probably the TestDisk might help with detecting Trouble at the Drive itself and otherwise you might be able to use the Disks too for testing, if pluging into Slot 6 normal controller and accessing the drives connected in Slot 7 anfter booting from Slot 6 with normal Disk and afterwards starting up programs from the patchdisk or testdisk and attempting the controller in Slot 7.... the images of the Disks are added at the right side of the controllerpicture...
clicking at the title of the controllercard links to a page with the entire german documentation - including the programcodes and the circuit plan from that controller...