Rectoverb 25 Head Reverb buzzing humming

[nom3d7]

I just bought a Rectoverb 25 head and Marshall 2061CX 2x12 cab and everything sounds fantastic! I have now noticed thought that when I dial up any amount of reverb I get a humming buzzing sound. It sounds like a 60 cycle hum but I'm not certain. When I turn the reverb dial (on the back) to 0 the hum goes away and the amp has no buzz at all. I've tried plugging into different outlets and even a power conditioner but nothing seems to make a difference. What could cause this to happen only on the reverb? Could there be something wrong even if the amp is 2 months old?

I've read some forums about guys having similar issues but could not find a clear answer. Some said that's just how it is other's replaced the reverb box.

I did also noticed in our jam room that our vocal PA had a slight 60 cycle hum coming though.

I'm wondering to test if I use a 12 volt battery with an AC Inverter to power the amp if that might isolate things?

 

[elvis]

Obvious question - what happens when you turn the guitar volume down with the reverb turned up? Does it affect the buzz?

There is a good chance that there is a tube related to the reverb circuit that is noisy/microphonic/sensitive to interference. Tube-rolling would be a good thing to try.

In tube amps, the most likely cause of failure is bad tubes. Regardless of the amount of testing of tubes, they can and will go bad at any time, no matter how new.

It is also possible that your reverb tank is picking up interference. Try turning off any fluorescent lights, and also try moving the amp to a couple different rooms to see if it affects the noise. Many people have their amps set up right next to a computer, refrigerator, or other source of interference and never think about that.

 

[nom3d7]

The volume of the guitar makes no difference to the hum. It will hum even without the guitar plugged in. I sent a ticket to mesa and they suggested swapping the 12ax7 tube that goes to the reverb tank. So I guess I'll try that and see what happens.

As for lighting, I tried turning off all lights and it did not affect the hum. I'm thinking I may take the amp to my home or different place and plug in to see if that makes any difference.