Probably not. I could probably have repaired them no problem (other repair services are available
) as could any good engineer.
It never ceases to amaze me the way many seem to think only the manufacturer or someone who once worked for the manufacturer can repair things successfully, but it simply isn't true. The only time that yes, "only the manufacturer can fix it" is true is in those small number of cases where a part specific to that manufacturer is needed and they won't sell the part to an independent repairer. In a typical valve power amp this would mean only the output transformer and maybe the mains transformer. All other parts are generic generally.