Opened up a Disk Unit Type-2 (dual floppy) and then one of the SMD-400's.
This what I found out:
- 3.5", 720 kByte/1.2 MByte, 80 Trk. (from system guide)
- 34 pin connector
- single +5V power supply
- +5V on pin 9 and 11
There is room on the PCB for a standard 3.5 power connector, but it isn't there. Without exactly seeing where Charlies extra cable is soldered to, I guess it is a replacement +5V.
On the hard disk side, I made some images of an 26-pin hard disk from an Toshiba T-3100:
http://fjkraan.home.xs4all.nl/comp/divcomp/26pinHD.html