Since they were old even then, and NZ was something of a computing backwater (on a training course I met a guy who's territory of 3 or 4 floors of the world trade center had more machines than my territory of half of the North Island) there were no formal training courses on them, and I was on my own with the manuals and the insights of the gray beards in the company lunch room.

It wasn't until I found Ken Shirrif's magnificent animated explainer https://ibm-1401.info/KenShirriff-1403Animation.html many decades later that I really understood how the machines I had been fixing worked.