Let’s face it. It can’t be very hard to do; or I wouldn’t be able to do it. No. Reading one is EASY. You need to be able to remember what a line looks like. And what two parallel lines look like. And what a wiggly line (or a rectangle) looks like. And a triangle looks like.
There are, maybe, a dozen or so symbols that represent components: resistors, capacitors, transistors, IC’s. They connect together with lines. None of this represents where they are in an amplifier, just how one component connects to another. So the whole technique of reading a schematic diagram involves following lines and finding where they go to. SIMPLE. But……
Why do engineers take so long to learn their job, if it is so simple? It’s because the reading is the simple bit. INTERPRETING…..well….that’s something else.
So your line (track/wire) goes to this transistor. Fine. But the amp doesn’t work. Not fine. So what can be wrong? what is it supposed to do, just there? Why is this voltage high? why does this chip put out dc? These are questions that happen all the time, and the schematic won’t help you to solve them. It tells you what connects to what, what the ‘what’ is. It doesn’t tell you what it is supposed to do or why it isn’t doing it. Now that is the hard bit.
I read some time ago that ‘a good engineer doesn’t need a schematic’. It was written by either a hyper-optimistic or woefully inexperienced bloke. Although I wouldn’t argue with the fact that we can repair without schematic diagrams, (carrying around a lot of generalised ones in our heads) I would argue that the customer will be charged a lot of money for the privilege, and that is an irresponsible attitude on the part of the engineer. It will take much longer without our trusty schematic. Which is why I frequently rail against secretive attitudes of amp manufacturers.