My mid-1980s digital alarm clock came with a full schematic. Can you imagine that today?

Actually, yes I could imagine that quite easily. Just buy "hackable" products which do that as a matter of course. A digital multi-purpose device with an alarm-clock form factor would not even be especially complicated to make.

That stuff is really cool, but this was a bottom-of-the-shelf model from K-Mart.

Of course nowadays something that simple could be a chip the size of a rice grain, power included. So that's something :)

Once things started going to multi-layer PCBs it was the end of reparability. It’s too bad because I have fond memories of fixing broken components on PC hardware and game consoles, even as someone who’s not an expert and simply a hobbyist.

> Once things started going to multi-layer PCBs it was the end of reparability.

Very true, however having full documentation would help nonetheless. My water heater electronic board cost over €250 to replace, although it contains less than €20 parts; a preprogrammed uC makes it impossible to replicate it. If it had public hardware and firmware documentation, someone could repurpose a similar but cheaper board or replicate the functions using a different rugged enough uC board, which would also likely bring down the retail price of the original spare part.

My understanding is that the new manufacturing techniques stop many people but usually not skilled technicians. It's component serialization, keeping schematics secret, and exclusive supply chains that are the real problem.