To debug electronics effectively, you cannot underestimate how much EE knowledge is needed.
Start with something like The Art of Electronics by Horowitz and Winfield.
An example of the kinds of EE stuff you don't heave to know to be an effective troubleshooter of basic issues, might be, oh, say, what it means for the poles of a transfer function lie in the left half of the s-plane.
As a counter, you can get amazingly far with little to no EE knowledge - depending on your troubleshooting skills and how modular something is.
A stereo that loses the right channel unless you push on the board? Broken solder joint.
Visibly exploded caps? Bad caps.
Some basic understanding of electricity and current flow and the high-level concepts will help, but a detailed education is more for building your own than just repairing existing mass-produced setups.
AoE is probably a good book for that kind of "beginner" who has a degree in a STEM discipline (or in the middle of getting one), but doesn't know electronics.
Start with something like The Art of Electronics by Horowitz and Winfield.
An example of the kinds of EE stuff you don't heave to know to be an effective troubleshooter of basic issues, might be, oh, say, what it means for the poles of a transfer function lie in the left half of the s-plane.