Newbee,
The act of turning off a component, often results in noise, without any component necessarily being defective. That is why one should not turn off sources or the linestage/preamp first, because any such transient "pop' will be amplified by the power amp, perhaps to destructive levels.
Sometimes noise in tubes is eliminated by the very act of pulling and reseating the tube. Often noise comes from poor contact at the pins, other times, something deposited on a surface inside the tube can be shaken loose and the source of noise eliminated.
Perhaps the best reason to have a tube tester is not to find out if a tube is beginning to go bad, but rather, to determine if a new tube is safe to use at the outset. I own a tester and lent it to a friend. The tester determined that one of the rectifier tubes he was keeping as a replacement showed no voltage drop in either direction (shorted); it is frightening to think what that tube would have done had he inserted into an amp.
The act of turning off a component, often results in noise, without any component necessarily being defective. That is why one should not turn off sources or the linestage/preamp first, because any such transient "pop' will be amplified by the power amp, perhaps to destructive levels.
Sometimes noise in tubes is eliminated by the very act of pulling and reseating the tube. Often noise comes from poor contact at the pins, other times, something deposited on a surface inside the tube can be shaken loose and the source of noise eliminated.
Perhaps the best reason to have a tube tester is not to find out if a tube is beginning to go bad, but rather, to determine if a new tube is safe to use at the outset. I own a tester and lent it to a friend. The tester determined that one of the rectifier tubes he was keeping as a replacement showed no voltage drop in either direction (shorted); it is frightening to think what that tube would have done had he inserted into an amp.