pavane -

My Google search (mainly because I was curious what an SD35 is) showed a few places that claim to have "hard to find drives" for "legacy Roland" machines, but nearly all that I found were US or Canadian based. Nearly all have a "no-warranty" disclaimer for such hardware, indicating it's likely to be "salvage grade."

As an example - NOT A RECOMMENDATION - Trycho has a banner at their site stating:

"WE ARE ONE OF THE LARGEST SUPPLIERS OF HARD TO FIND LOW-DENSITY (DD) BLANK DISKS FOR OLDER SEQUENCER MACHINES. WE ALSO HAVE HARD TO FIND REPLACEMENT DRIVES FOR OLDER ENSONIQ, ALESIS, KORG, AND ROLAND MACHINES
GIVE US A CALL OR EMAIL! 1-800-543-8988 (U.S and Canada) trycho@trycho.com"

(Check out their (NO) Warranty disclaimer at the bottom of the page.)

I found a couple of SD35 units for sale at about $800 (US) and a few more at auction sites (eBay etc) showing as low as $325, but these may be just "current bid" prices - I didn't check to see whether they were near closing.

If you're considering a (Roland) replacement, you might get some help from the listing at Roland sounds. "This section includes commonly available new and second hand synthesizers, samplers, sound modules and master controller keyboards."
(Note that I found this page a lot easier to read after a "Copy" and "Edit – Paste Special – unformated text" in Word.)

The "rolandus.com" company page is unable to find the SD35 using their search engine, and I can't even identify a category of currently listed Roland products that looks like it.

If the SD35 truly can't use an HD floppy drive, it would imply that the driver is in a BIOS chip of some sort, and it would seem they should have a "flash" to allow use of a more available floppy - but no luck there.

I did find a couple of "support chat" groups where people complained about the SD35 being finicky about disk quality, and 2D disks are likely to be subject to some aging, since hardly anyone makes them any more and they're likely to be "old." A simple machine like this might report the same error for a bad disk as for a bad disk drive. One fellow in particular noted that his Mac could detect and skip bad clusters on the disk, but his SD35 "requires a perfect disk" and he was having problems getting them "perfect enough." (posted about a year ago.) His "analysis" was a little "newby" and somewhat suspect; but if your machine can read some disks but not others, you might suspect problems with the disks rather than with the drive.

There are archaic techniques for isolating bad clusters that format doesn't detect (by writing "dummy" information in them) that might be used to see if this is a problem, but since you have to do it individually for each disk it's not very practical for actual use.

Repair and maintenance of floppy drives used to be fairly common, but is probably a "lost art" for most maintenance people now. With 5.25 floppies, you could get "cleaning disks" but with the small floppies you usually have to open the floppy drive case and use a Q-tip with a drop of alcohol to swab the heads (gently, of course). Be sure the cotton tip doesn't leave strands behind. It is important to get any "loose crud" in the whole machine (inside the drive case) cleaned out, but the stuff that sticks tightly enough to resist a gentle blast of air probably won't hurt anything, unless it's where inserting/removing the disk might shake it loose. Non-functional surfaces can be wiped with the alcohol dampened swab.

People used to try to adjust tracking of the floppy drive heads, but this requires software (and skill) not easily obtainable now. I can't recommend that you start bending the head arms to try to do this. If the SD35 can format its own floppy, you might try formatting in the SD35 and then see if your computer can use the disk without reformat. If it can, the head tracking is "good enough" although you may want to format disks in the SD35 instead of in the PC before recording for best readout.

The SD35 gets pretty good ratings in the few descriptions I could find. I'm puzzled by the difficulty of finding even a category of similar machines in current stuff at Roland.

John