It is a tube product which means that the circuit is most likely relatively simple and that any repair tech that is good at working on tube gear should be able to diagnose and repair the problem as long is there aren't proprietary parts.

If that doesn't work I believe that was Anthony Michaelson of Musical Fidelity's first company. Maybe try contacting the Canadian importer of Musical Fidelity. They might go the extra mile to offer some assistance, or advise. Failing that try contacting Musical Fidelity directly.

Update:

The unit is fixed after several years of trying. The highlights of the ordeal below:

• did on-line search for similar problems
• this led me to a lead - Papworth in Britain, they took over the design of M & A amplifiers including a TVA-10 like integrated
• their head man (Eddie Fincham ?  can't quite remember) provided some very good advise for the tech to check. Still no luck.
• contacted Tim de Paravacini (now with EAR), the original designer of the TVA-1 and TVA-10 for advice. His response was basically, "he did not have time to address problems with a 30 year old design...." fair enough.
• Musical Fidelity was not contacted (advised that this would be futile)
• The unit sat for another year, until I ran across a teck in Edmonton who used to sell these "in the day" and has a experience in fixing tubed equipment. He fiddled for about 8 months and discovered that a large number of discrete components were well out of spec. (even for parts this old). This caused the unstable bias and the extra heat which further "baked" the components. He replaced all the suspicious parts, slapped in some cheep tubes and the unit was good to go.
• months later a resister failed but this was a quick fix.

The unit is once again producing sweet, sweet music.

Neil D.

now that is what i call percervierance.  way to go.  glad you have your old amp working again.  the internet has been the cause of much bad, but also as in your case, much good too.