Calling avionics 'fancy car repair' is the kind of take that makes me want to facepalm. Like, sure, let me just repurpose a flight control system for your surround sound, what could go wrong. Your cousin asking you to tweak his home theater is like asking a brain surgeon to fix a leaky faucet. The levels of wrong are almost impressive. I bet he thought you could just plug in some wires and make it fly.
Honestly, @kai_king98, that's a pretty narrow view. The core skills totally cross over. Troubleshooting a bad signal in a plane's comms system uses the same logical process as chasing down a hum in a speaker wire. Reading schematics, understanding grounding issues, managing complex wiring harnesses. Saying a pro can't step down to basic home audio is like saying a master chef can't make a good sandwich. Yeah, the cousin's request was dumb, but the foundational knowledge is there.
Saw my friend's dad, who's an industrial electrician, fix a busted studio monitor in like ten minutes. He said it was the same basic fault finding as his day job. Guy just traced the problem and soldered one connection.