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.