Maybe there’s someone still at Lyric HiFi that can help you or inquire within Lexicon for the answer. Didn’t the Lexicon line under Harmon International take over Madrigal when they closed the doors? The original owners of Proceed were the Lyric owners I believe. You probably will not have any luck contactIng Harmon or Lexicon but Lyric might or if they have a service department they might have the service manuals.
212-439-1900