I'm with you. I like to know the why , what and how of the components. I learned a lot through the Navy but needed a primer when I got back into pinball and started doing board repair. This book is pretty good and uses physical experiments to show you how it all works from batteries to integrated circuits.
http://www.makershed.com/products/make-electronics-2ed
As for a buzzing machine, most can be eliminated by good grounding and a new volume pot.