This brings back some memories. When I was a young trainee engineer back in the mid 80's I worked at a Data General (DG) broker/repair shop. One common job we

This brings back some memories. When I was a young trainee engineer back in the mid 80's I worked at a Data General (DG) broker/repair shop. One common job we did was refurbishment of DG Phoenix and Gemini drives. We sometimes had Diablo's, which is the drive make in the Alto video (possibly a model 30) and Zebra units (these were monster multi-platter units). The ones I worked on were the Phoenix and Gemini drives (models 6045 and 6050) and were known as 5+5's (MB's) and 10+10's (MB's) meaning that they had a fixed platter, usually carrying the OS and you could top-load a single platter cartridge. There's quite a good picture here with one of these drives in the drawer out position : https://en.wikipedia.org/wiki/File:Data_General_NOVA_System.jpg https://en.wikipedia.org/wiki/File:Data_General_NOVA_System.... There was a plastic lid you'd put on top of the cartridge which is why you can't see the cartridge release handle in that picture. Normally you wouldn't be able to spin up the disk unless the chassis was pushed back into the rack, however the spring loaded "drawer open" sensor switch could be pulled back a notch towards the rear of the rack so that you could start the drive for service/repair work. We used to do head replacements, re-alignments and fix head crashes. As was mentioned in the video, so that you could ensure that a cartridge could be reliably used across different disk drives you had a special disk that contained servo tracks which you would align the heads with. I think there were two, possibly three servo tracks on this disk (my memory is a bit vague). There were test points on the electronics you'd hook a scope up to so that you could check the alignment - there would be various pot tweaking to get things just right. Once you thought you had things "just so" the next step was to run the exerciser tests from DTOS (Diagnostic Tape Operating System - yes we booted the diags from tape) or ADES (Advanced Diagnostic Executive System). The Gemini and drives also had these huge linear motors that when in full test mode (seek tests in particular) were quite scary things to behold. This video gives you sort of an idea: https://www.youtube.com/watch?v=qZsHTWiI0-4 https://www.youtube.com/watch?v=qZsHTWiI0-4 We used to do regular trips from Scotland to London with a pair of Phoenix or Geminis in the company Sierra estate (1st generation). These things were so heavy that you really had to think about your braking distance once up to speed :) That poor car eventually had to have its chassis around the tailgate re-enforced after a few years of battering up and down the motorway with all that big kit in the back. Fun times though.