I want to start repairing amps. how do i learn?

you need to go to school.there are some on line electronics schools,but the practical part is needed.
i did warranty work for rockford fosgate.they use surface mount devices and you have to be an expert to repair that stuff.

research my friend. start reading up on circuitry. electrical properties, ect. Learn what different components are and look like and what they do. Know your definitions such as terminal, capacitor, circuit board. You can find all the information you need online. Be careful, not only for your own safety, but the saftey of what your working on. Be observant, look for problems on the circuit boards, frayed wires, melted parts. Get yourself a Multimeter and a test light. Learn to use the multimeter to check for continuity. It is a skill you will have to learn, its not instinct. With a little research, knowing how to use a few simple instruments, and the power of deduction, you'll be a wiz in no time.

You will need to enroll into an electronics school to learn how to repair electronics on a component level.