Part 11 of a series: DEC PDP-11/23+ Restoration
The PDP-11/23+ was typically housed in a BA23 chassis containing an RX50 floppy drive and an RD52 hard drive. These drives are installed in the front of the chassis and connect to a special signal distribution board that, in turn, connects to a DEC controller board (M8639). One of these boards was included with the original eBay purchase and, like most of the other components included, it only required a bit of cleanup.
The RX50 is a dual 5-1/4″ floppy drive. It’s a very unique design in that both drives share an enclosure and a motor! I eventually figured out that the top, or data sides of the floppy disks need to face the middle of the drive. I haven’t cleaned the heads yet, but it’s on the to-do list.
The RD52 is an MFM 5-1/4″ hard drive with a storage capacity of 33MB, which was huge back in the day. It’s pretty much a standard hard drive of the era and DEC repackaged drives from several vendors like Seagate and Quantum.
The BA23 chassis, like most other DEC equipment, is built like a tank and heavy. I’m impressed by the quality of the hardware and modularity of the system. I guess this was part of DEC’s need to reduce the cost and complexity of the machine in order to compete with IBM.
I hooked up the drives and powered up the machine. It works!
It’s starting to come together!
Update (2022.10.25): Since I’ve located and switched over to a proper BA11 chassis, I think I’ll abandon the MFM and floppy drives in favor of the more historically accurate RL02 drives.
Head Spin Labs 
If you need an emulator for the RD52, may I recommend https://www.pdp8online.com/mfm/mfm.shtml . We used those for a recent retrocomputing project (also PDP-11/23-based, by coincidence — not “+” in our case). The developer was very helpful with software mods, including adapting it to our oddball non-DEC controller’s sector format. (Nice design touch: it also emulates the 5.25″ drive’s physical footprint, so it fits right into the original drive bay.)
As you say, such old drives are no longer for everyday use. Purchased new in 1982-84, so going-on an order of magnitude beyond their 5-year design lifetimes. Our hearts were in our mouths every time we spun one up, never knowing whether, this time, it would give up the ghost. *Very* relieved to finally get the irreplaceable (and of course, not-backed-up) data off of them onto the emulator!
Two of them took heroic effort, described here: https://forums.theregister.com/forum/all/2021/01/04/who_me/#c_4180191