| There is absolutely no way for us to know without at a minimum seeing detailed closeup pics of the board; and even then, most electronics diagnostics can only be performed in person.
Plus, Boss has made a few different phasers over the years, and it matters which one you have. So, which one do you have?
If it happens to be an older analog one that used thru-hole components, and if the chip(s) inside is/are still in production, then you may be able to rebuild it with new components. If it's digital, or uses SMT/micro components, or if any chips inside are out of production, then it's nothing but a paperweight now.
You could salvage the case if you wanted to build a totally different circuitboard from scratch, but it doesn't sound like you're at that level of tech yet. | 
