If you really like the unit, do some research ahead of time and replace all known-to-go-bad transistors, all electrolytic and tantalum caps, possibly bias and offset trimmers, and any resistors that have drifted. In units of this age, only fixing the current problem on guarantee another issue to present itself in the future.
I recommend that someone should not buy vintage unless willing to take the time and money to bring it back to spec. In the long run it will be better than having to continue fixing issues and it "nickle and dime-ing" you to death.