Electronics Concepts for Beginners?

Does anyone know of a good resource for electronics concepts for beginners? I’m a game repair hobbyist for my personal collection and occasionally for friends. The most I can do however is some “assumed” continuity testing and replace a capacitor or two. However a lot of what I do is mostly assumption based on what I’ve seen others do. I don’t actually have that deep of an understating on basic electronics. I would love to be able to more accurately pin point specific problems with game cartridges and mother boards. For instance, I don’t exactly know what each component is actually doing with the signal and what is normal and what is an issue when trying to find problems on a board.