hey there, just bought a Peavey JSX 212 combo, and so far I've encountered 2 problems:
1. inside the cabinet, right beneath the fuse, there is a black box-like object (not sure what it's actually called sorry!) and when I play with the bass up past about 6, and at higher volumes, it vibrates and creates this annoying sound. Is there anyway to fix this?

2. The amp has a hum on all three channels even if the master volume is completely turned off. Is this maybe a tube problem? I'm sorry if these are terrible descriptions, or if this is a simple fix, this is my first tube amp. I'm a newbie when it comes to this.

Any help would be very appreciated!

Does that amp have reverb? Sounds like a reverb tank.

Pics are really really helpful, you should get some up.

Could be tubes, could be bad power in your house. Do you have a power conditioner? Normally to lower noise floor we recommend a JJ ECC803 in the V1 position, but it's not a great idea in a combo amp. Since the speaker is so close to the chassis, vibrations can cause the ECC803 to go microphonic prematurely.

If you don't have JJs in the amp, get a few and replace all your 12AX7s with them as a start.

Then look into getting a power conditioner.

Oh, also first try the amp in different outlets in your house first. If there are too many things drawing current on one breaker, that can be the cause of subpar power conditions.
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I'll try and get some pics up tomorrow. And now that you mention it, it just might be the outlet. It's been plugged into a powerbar with a couple other amps, so I'll try it elsewhere. If that doesn't work I'll look into the other things you mentioned.

Thanks for the response, really appreciate the help!
alright, a few people recommended I try tapping the preamp tubes with a pencil to see if that causes any heinous noises to come out of the amp. When I did this, nothing happened. So it seems the preamp tubes are ok.


that's basically what the back of my amp looks like in case that helps at all. The thing on the left right below the signature has wires going into it that vibrate when I hit certain notes, which was the vibration problem I was talking about. I think I'll just have to tape them to hold them in place or something
oh and yes, the amp does have reverb, and when I turn the reverb all the way up the hum level does go down, but it doesn't stop completely
All tapping the tubes does is test for microphonics. A tube can hum and not be microphonic.
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oh ok, that's good to know. I think I'm just gonna take it into the tech this weekend, I don't trust myself to **** with it too much. Still got a lot to learn with these tube amps obviously
That black 'box' on the left is the Power Transformer. I wouldn't mess with the wires on that. Who knows what's wrong. Weird that the hum goes down when you turn the reverb up. I'd try unplugging the reverb tank altogether and see what happens.

It also kind of looks like maybe the Output Transformer has been replaced but I haven't seen enough combos to know one way or the other.

I do know that the JSX has had problem in the past with faulty (power tube) sockets.

I really think you should just take it to a tech though as you've already considered.

Good luck,
I second 311. But before you bring it in disconnect the reverb tank. They are just like two rca jacks and see what happens. If all you do is disconnect the tank itis safe.

If nothing changes bring it in.
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I had this problem with my TSL100 yesterday, I turned the amp on and tapped the preamp tubes.. seemed to solve it. Maybe dirty connectors or something!