Dizengoff D4 problems and questions

My Dizengoff D4 mic pre hasn’t worked in a couple of years. (Redd mic pre wannabe) Anyone know where I could get it repaired without a schematic?

Sounded great when it was working. First symptom was significantly gain than previously with occasionally no gain at all. Sent it back to Dizengoff while they were still open where it never really got fixed. Maybe they were in turmoil and going under at that time. Matt Newport himself worked on it and thought he had solved it. Came back still intermittently not working so he sent me a new gain pot circuit and now it’s completely dead.