I have a few PowerBooks: a 140 (that doesn't work), a 520 with a PowerPC upgrade, and a Duo 230. I accidentally damaged the ribbon cable for the floppy drive (which I will soon replace) while unjamming and lubricating the floppy drive in the 520, and the PowerBook Duo doesn't have a floppy drive. So, I decided to order an external HDI-20 floppy drive, to temporarily replace the PowerBook 520's floppy drive, and for use with the Duo. The problem is, I didn't realize that all of my PowerBooks use the HDI-30 port, instead of HDI-20, until my package with the external floppy drive arrived today. Unfortunately, the buyer doesn't accept returns, and reselling it likely wouldn't be a great option, since I can't test it, nor could the buyer. I, rather short-sidedly, just assumed that I would be able to fix most of the problems that could have occurred with the drive. That means that I am stuck with it, and can't properly use it until I get another PowerBook with the correct HDI-20 port, so I am looking for suggestions with what I could do with it, or ways to use it!

You can use that external HDI-20 floppy drive with your Duo 230 with a Duo Floppy Drive MicroDock Adapter.

Not terribly expensive on eBay:

The Macintosh HDI-20 External 1.44MB Floppy Disk Drive was originally released for the PowerBook 100. The only other PowerBooks that can use it are the PowerBook Duos ...if you have a dock of some type that has a HDI-20 floppy port. There were third party options other than the above, the only other Apple dock that has a HDI-20 floppy port is the Duo Mini Dock:


Which also does quite a bit more.

Hope this helps.

You're right! I already have a Newer branded SCSI MicroDock for my PowerBook Duo, but it has an HDI-30 port. This lead me to assume that other SCSI docks I would find for the Duo would also be HDI-30, but I guess I was wrong. Thank you very much for telling me this!