Ask HN: How can I break into retro computers?

I grew up in South America where computing culture wasn't really a thing in the 90s and 2000s (at least in my neighborhood). After many years of programming and browsing through HN I've gotten interested in getting an older computer that I can "fully understand." I want to be able to take it apart and know how the CPU, memory and graphics works all the way up, something I don't think is possible in a modern computer. I also think they just look cool. I've seen some people mention the pdp11 and Vax machines. Any thoughts?