3 years is actually a long time for power tubes to last. They can last longer, but usually ~2 years is the average, for a non gigging amp. The vaccum cleaner being ran could definitely played a roll in how the amp was acting. I've heard all sorts of pops, clicks, and hisses and such when certain appliances come on/off, etc... I would say that it's about time for a tube change. Dieing power tubes can cause all sorts of funky stuff to go on with an amp. They can blow fuses, cause a loss of volume, cause unwanted noises, etc...