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Mesa 2:90 power amp is humming loudly


LIVEtoROCK86

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Hey everyone. So my Mesa 2:90 power amp is humming. First, lemme give you a run down on my set up. It's simple...I run my guitar into a Rocktron Chameleon 2000 and that runs into the Mesa. Done. When I flip the standby switch to ON on the Mesa, it hums and as I turn the volume knob up of course it gets louder. What I've been doing to compensate is turn the volume down on the Mesa to reduce hum and crank the volume on the Rocktron, which helps, but still...I'd rather pump the volume a little bit more on the Mesa. I had the amp serviced in March...tubes (power tubes, not preamp tubes) changed along with some circuitry (something burned in there! so I figured it was time for a fix). It was fine after the fix...but now the hum is slowly but surely becoming more present with each use. I'm in a band and am recording very soon so this will become an issue. have you guys had this problem before? Is it a simple fix? I've checked the cables...it's not them. The power tubes were already replaced. Oh another piece of info is there are only tubes in Channel A and I only use that channel. Channel B isn't being used (volume is all the way down since you can physically turn it off). The techs said that was fine.

 

So....any suggestions???

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Yea I figured it was a tube problem...but you said its the 12Ax7's? Do those create a humming? I thought they created more of a hissing...I'm not sure though. I don't think it'd be the power tubes because those were changed only 6 months ago...

 

 

12AX7's can cause hum also. Also, tubes can go bad at any random time, so it doesnt really matter how new they are. I've had some die in like a week, so you just never know.

 

The only circuit related thing that normally causes a lot of hum is bad filter caps. But, I dont think those units are old enough to have that problem.

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