Well, I checked my HQ manuals and schematics folder and it's not in there. However, if the only thing wrong with it is the monitor and volume, you probably won't need the schematics (but hunting down a copy for the future probably won't hurt. If one isn't available on the 'net, you'll have to phone some arcade companies in your area or the manufacturer themselves (if they are still around. It is manufactured by a company called Project Support Engineering and they haven't made a game for nearly 30 years).
I'd say grab it... If you are like me, you've probably invested 50$ in worse things. (I didn't remember that game until I saw the scoring instructions on KLOV. I used to play that game when I was a pre-teen. Coolness.)
APf