@raggah. I don't believe that you contacted George Meyer AV repair facility in Los Angeles, CA.
They are an authorized Mark Levinson repair facility and a simple call would confirm this.
I have had two Mark Levinson 23.5 amps repaired and one ML3. Also many Audio Research pieces.
Also, just for your information regardless of whether a technician is authorized or not, a good technician can diagnose and repair. Unless the parts are simply not available.
I know for certain they repair 331 amps.
Their website list the following.
Authorized Audio Research Service and repair
Authorized Levinson Service and Repair
Authorized McIntosh Service and Repair
Authorized Krell Service and Repair
Authorized Wadia Service and Repair
Authorized Hegel Service and Repair
Authorized Jadis Service and Repair
and if you click on their link, they list about eighty brands they repair.
Also, speaking to their technicians, they stock hard to find parts.
Anyway, I'm not affiliated with them other than being a many times customer, but it is good to know of a repair facility that I can trust.
enjoy