Looking for resources on the basics of Heavy Equipment repair

I'm looking for some resources to familiarize myself with the basics of heavy equipment repair and maintenance. I'm an apprentice operator that spends a fair amount of time in the shop when I'm not out in the field operating and right now if I'm in the shop I am either welding/fabricating (the field from which I came) or helping mechanics. I am good with my hands, so I have no trouble doing what they tell me, but I lack a good understanding of why I'm doing the things I am and I definitely don't know how to diagnose an issue. Now, I as I said, my primary focus is on operating equipment so I'm not required to learn mechanics as part of my apprenticeship, however I like to learn and I like to do a varied amount of work, so I'd like to at least be able to understand basic mechanics topics. Can anyone recommend any books, videos, etc. that I can use after work hours to step my knowledge up?