Typically, when checking out a PCB, I will immediately check all IC, or "Intergrated Circuits", by putting the part number in an online search engine. There are a few I'm always looking for as they are commonly used in the building of simple synthesizers, and these are **Op-Amps** and **CMOS logic chips**. Additionally, you could be lucky and discover a microcontroller, allowing you to flash your own program. To my surprise I found a microcontroller in a LED lamp, but I haven't managed to figure it out yet.
Not only are loads of schematics published online based around (oddly specific) IC's, they tend to break very fast. I cannot count the number of time the number of times I've accidently put a chip in upside down, causing the + and - to be flipped, and burning out the chip within seconds. In a world of plenty you'd just replace the chip with a new one, but in the reality of working with salvaged hardware, this is not that easy.
