i need to test my tubes, iv'e got buzz/hum, other web sites say pull them out one at a time untill you find the one that makes it stop. dumb question but how does that work... wouldn't the amp just stop working entirely with out a tube in it?
If its not fender than whatever]
Tap the preamp tubes with a pencil with the amp on. If you can hear the taps through the amp, replace the tube.
Bad power tubes don't generally buzz (sounds more like a ground issue than a tube problem to me), but you can always replace them and see if that helps.
they can still be producing hum and buzz with out being microphnic right?
If its not fender than whatever]
Buzz? No.
Hum? Maybe. You could buy a couple preamp tubes and try swapping them for yours.