Valves go bad - even new ones (in fact, new production are more likely to go within the first few months - if they last through the burn in, they will likely last a few years).
Just let them swap out the faulty valve (or set if it's a power valve). If it goes again, let them get it fixed or swap it out for something else.
Gearhead wrote
Why would you buy an amp like that new? ???
Well
someone has to. WHere do you think second hand stuff comes from? ? And a lot of guys like to know the history of an amp and have the manufacturer's warranty.
