Well, first thing is: you got to have an amp tech you TRUST. And if you don't have any you know yet, you look for advice from someone you trust (including on this forum or the TDPRI). Once you have an amp man you trust (from experience or hearsay) you take the amp to him with a set of fresh tubes and he'll do the right things – period. Or he may have the tubes… phone him first. That's my experience and never once have I been overcharged or disappointed. There may have been difficult repairs, but we worked through them – my trust of my tech being a key part of the recipe: I've never double-guessed him and heeded his advice. I'm happy, my amps are happy, my bands are happy, he's happy. If you lived in Milan, I'd direct you to him… a passionate, honest tech and has become a friend over time. I'm sure there's plenty like him (or nearly like him ) all over the US. Once you find a good one, it's for life.