Bugera
When my brand new Crate V50 new style, Spuds, blew up after only two months, not to be found repairable, the Crate engineer advised me that a power tube from a bad, supposedly, run of tubes, Ruby I think, blew and catastrophically. Resulting in destruction of the power supply and capacitors and other components. Working on those tubes was probably a very good idea.
It was a great sounding and playing amp.
I made out great though because the Crate guy told me he would refund my check for 164 I paid getting the amp from MF on sale, and I replied that I would be better off if he could find a Crate amp laying around the headquarters or in the warehouse that he could send me, even if a big nice solid state one, but that I would love a Palomino V32 or Palomino V50. He told me he had a brand new V32 212 NOS that he would send me. I jumped on it and had it in like two days along with the invoice for 799 dollars that I didn't have to pay, it was just for inventory tracking of the replacement amp.
The Palomino V32 212 is an awesome amp.
What I learned is: I heard a popping sound once or twice from the power tubes and ignored it, brand new V50 new style, unreliable switching power supply, etc. The next day it blew up catastrophically, not to be repairable. Crate was awesome in dealing with my warranty claim.
So, therefore, I would advise to be extra careful with a tube amp and when you suspect a tube problem, get right on it and have a tech check it out or replace the tubes with JJs or something great and have a tech bias it correctly, not too hot or anything like that. I won't mess around taking chances with suspectedly failing tubes again.