In truth, it's only in college that a fault finding solution get's looked at in detail.
When I started work fixing stuff (I don't do it anymore) the instructions were: 'Replace all the obvious components, all semiconductors and IC's, if that don't work, replace the board.' It's cheaper to do that than spend hours proving and rectifying a complex fault. Fact is, time costs more than electronic components.
However, if you have the time, it can be a very interesting process, dicovering what's exactly wrong. Won't earn you much money though