The OB8 was my first major repair endeavor, I learned a lot from itZ wrote: EDIT: Sorry, I confused the OB-X / Xa's innards with the OB-8's. adhmzaiusz was correct, that there are only 2 voice boards, but each voice board has all the components for a single voice arranged in a rectangle in a fashion similar to individual voice boards of the OB-X / Xa.
IMO the OB8 is an extremely simple synthesizer inside, at least as far as the voice boards go. It's a very nicely laid out circuit board and it really helps that all of the ICs are socketed. There are no rare parts other than the CEM's, all of the 74LS logic chips are very easily obtained.
My only advice when swapping out IC's in this-- don't bother with an IC extractor they are more trouble than they are worth. Best thing I ever learned to remove them from the socket is to use a tiny flat head screw driver and gently pop each of the short ends of the IC little bit by bit until its free. Just a little bit on each side until it comes loose, this will keep the pins from bending too much.
Years ago in my learning experience I made the mistake of trying to pop one of the EPROMs using the extractor and one of the legs broke off, it was a pain in the a*s to carefully create a new pin without damaging something else. But anyway go ahead and make mistakes, learning how to correct them makes us strong!