After many delays and false starts (it's been almost a year already? 😮 ), I was finally able to do some testing of the CD7.
I first tried the Future Domain TMC-1680 ISA SCSI card. Setting the jumper block was easy; installing drivers was a bit laborious (had to do a New Hardware search for Windows 95 to find the card and add the CD7 DOS ASPI drivers manually). I succeeded and got everything to work, but my Socket 7 PC slowed down quite a bit. Not a good sign 😦 . I only installed the PowerSCSI! DOS 4.1 drivers from the floppy; I did not install anything from the CD (everything there is for Windows 3.x anyway).
Next I installed the Diamond Fire Port 40.

Much easier this time, Windows 95 found it right away and asked for drivers (still had to add the CD7 DOS drivers manually). With this setup working I saw the computer return back to normal performance levels; CD access was a bit odd however - sometimes the CD7 would stop and retry reading the inserted CD for no apparent reason. Hmm 😒
Last but not least, the Adaptec AVA-2906.

Since this SCSI card has a 25-pin external connector (the Fire Port 40 and TMC-1680 have 50-pin connectors) I had to get a different SCSI cable to match. Installing drivers was pretty much the same as the Diamond card, but operation and performance of the CD7 appeared to be much better - got up to speed a bit faster and didn't stop/retry to read any CDs. Very nice 😊
So why did I have to add the CD7 DOS ASPI drivers by hand? Because the setup program couldn't do it. For some unknown reason it kept telling me to add needed entries to both Autoexec.bat and Config.sys, which I did; after a reboot, the CD7 was fully accessible and functional. Incidentally, both CD7 floppies actually have drivers and utilities; the first floppy has standard drivers that list each drive slot with a single letter (7 drive letters in total); the CD PATHfinder floppy has a driver that creates a single drive letter and lists the 7 drive slots as virtual directories; each CD gets listed and associated with the slot it was used in last in this manner. It's a neat way of saving drive letter usage and while it works well enough with productivity and media applications, it's not very compatible with games (Warcraft 2 and Whiplash complained constantly about not finding the CD, Creature Shock lost track of where the CDs were 😖 ). The utilities are meant for Windows 3.x and did not try them. As for the CD7's performance, it's what I expected of a 2x CD-ROM drive - not very fast, but steady and spot-on (FMV games do have issues like skipping and freezing); it is noisy however because of the tray loading system (it is also very fast to load/unload a tray).
Before I started testing the CD changer curiosity got the best of me and compelled me to open it to see what it was like inside. The CD7 has 5 screws holding the top cover, 2 on each side and one on the back; they were very tight, but some gentle persuasion with a Phillips screwdriver got them loose. Here's what I saw:




This thing is jam packed, there's hardly any empty space left! That explains its weight (almost 4lbs 😮). Most of the space is taken up by the slot loading mechanism; I did spot a couple of fuses and some large capacitors at the back.


(Sorry if the pics are not very good, it's very difficult to take them in such enclosed areas)
As interesting as it was to test the CD7, I can't use it on a daily basis. I don't have a permanent area to keep it plugged in, is cumbersome to setup externally and fairly large to keep around.

These pics show how big the CD7 is; since I don't have the room, I'll have to go back in storage for the time being. It was neat to have up to 7 CDs available all the time however; if my current living arrangements change in the future and I get more space, I might consider having it around with my Socket 7 PC in a more permanent setting. We'll see.
P.S.: I made images of the CD7 floppies, PowerSCSI! floppies (WinImage 5) and CD (Imgburn) and uploaded them to my Dropbox account. Here are the links for anyone that wants them.
Mountain CD7 CD-ROM changer drivers & utilities (two 1.44mb floppy images):
https://www.dropbox.com/s/jg27gr5q5vkrvbg/CD7_FDI.ZIP?dl=0
Future Domain PowerSCSI! drivers (two 1.44mb floppy images):
https://www.dropbox.com/s/o0bl55kg0q0dg0t/FDPS_FDI.ZIP?dl=0
Future Domain PowerSCSI! bonus software (one 247mb CD-ROM bin/cue image, has two CD audio tracks):
https://www.dropbox.com/s/16iyyujgoka92yq/FDPS_CDI.ZIP?dl=0
In case anyone is wondering I don't have a VOGONS Driver Library account, and at this point I don't expect to ever get one. Sorry 😐