Not the submitter, but just for context, this is a post by the admin for the groups.io community for users of Tektronix oscilloscopes and related test equipment, answering a query from a user looking for service documentation on an instrument from the 1990s era, somewhat newer than most of those discussed on the group.

Service manuals from Tektronix, like those from Hewlett-Packard, used to include what amounted to a BSEE lab syllabus in their service manuals. They would include full schematics and operational theory that often went well beyond what was needed by a technician who was tasked with maintaining the gear. Often the documentation was written by the design engineers themselves, who were the Michael Jordans and Kobe Bryants of their field. The educational value of this material was (and is) immense. Not only could you get your scope up and running after spending some time with these manuals, you understood a lot about how it worked and what motivated the underlying design decisions.

Dennis is right in that this wonderful literature went away well before its time, but I think he undersells the other side of the argument, which is that these manuals would inevitably become less useful over time as well. It was true that management became less engineering-driven in the 1980s-1990s period, which was both unfortunate and avoidable, but it's also true that over the same timeframe he's referring to, companies like Tektronix and HP had to migrate to custom ASICs and software-heavy architectures that were inherently less user-serviceable.

These aren't like products from manufacturers like Apple, Tesla, or John Deere whose overt market abuses have spawned the right-to-repair movement -- they're the tools used by the people who design those products. The instrumentation companies had to stay well ahead of the technology curve, just as they do now, and increasing integration often has the unfortunate side effect of making the inner workings of the product less accessible to the user. Personally, I'm not sure things could have evolved much differently than they did, regardless of the ratio of MBAs to EEs in management.

Bummer, too, because those manuals were AWESOME. One thing that is indisputable is that both Tektronix and HP stopped publishing component-level service manuals about 5-10 years before the technology justified it. Because their technology had to stay ahead of the market, a lot of gear that is still very useful in many applications today is now almost impossible to keep running.