Create continuity tester circuit with buzzer and LED for check solder joint defects, not kill components on PCB, as probe gives tiny current and voltage.
Imagine your dad is old. Sure, he hears anything weak sound. How do you do? You are an electronics inventor, right? Yes, you can try to make a tool. To help him back to listen to great music again. This project is small, use only one 1.5V battery. Using normally components you can buy in stores near you.