Whether you are a musician looking to repair your own instruments and other gear or if you are a technician there is one thing that we all can find useful and that is the schematics of a product.
Suppose you want to create an audio circuit or if you wish to repair an audio product, this process would become much easier if you have detail schematics on your hand.
That said sometimes it might just be time for something new but if you want to keep up the diy spirit then you should look at the best diy guitar kits.