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Harmonic Components


unclej
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before i put the alamo back into it's cabinet the other day i discovered something that's got me curious. the amp was powered up and connected to a speaker. i was gently tapping around on all of the components, wire connections, tube pins, etc. looking for any loose connections. when i got to the bass channel i was tapping on the lugs of the pots and when i tapped one of the wires leading into/out of the pot it made a noise. it wasn't an electrical popping like a loose connection. it was a harmonic noise heard through the speaker each time i did it. the wire led to a small tag board. each of the pots had a wire going to it and connecting to a couple of resistors and a capacitor each and then going on to a tube. most, but not all of the components on the tag board did the same thing when i tapped them. a hollow, harmonic noise heard through the speaker.

the bass channel sounds fine when a guitar is played through it. there's no excessinve humming. so what could cause such a thing and is it something i need to correct?

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thanks steve. actually i was using a chop stick per gerald weber's suggestion in one of his videos. i watched it again last night and had missed one statement that some harmonic in that area is normal and nothing to worry about.

and lk, as usual you're right on. one of the 12ax7's was very microphonic and when i replaced it there was a reduction though not total elimination from the components on the tag board.

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that sneaky rascal probably got the idea from you..you'd think he'd be descent enough to give you credit. :D

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