Reverb is buzzing

[bird_droppings]

Just got the new Mark V delivered today and have been hugely enjoying tweaking it in various ways and trying to create specific sounds.

But.

It's been very noisy, and I suspect something is wrong.

In particular, when I turn up my reverb until it is straight up (12:00 o'clock), the clean channel makes a static sound much like an AM radio on a bad station.

Surely, it's not supposed to do this?

Do I have a suspect tube?

Thanks for your help in advance!

 

[eudaimonia02912]

Tubes V4 and V5 control the reverb. Try replacing those one at a time and see if the problem goes away.

 

[Scary]

It's certainly not supposed to be like that. I have no noise with the reverb.

 

[bird_droppings]

I was thinking this wasn't right.

How do I get to V4 and V5? All of the 6L6's are in the way...

 

[SteveO]

I was thinking this wasn't right.

How do I get to V4 and V5? All of the 6L6's are in the way...

You'll have to pull a couple of the power tubes to get your hand in there.

 

[bird_droppings]

I was afraid of that.

Is there anything in there electrically hot that I should be careful not to touch?

 

[eudaimonia02912]

You should do this when the amp is turned off, since you have the pull the power tubes. As long as the amp is off and the tubes are cool, don't worry about it. You won't electrocute yourself from changing tubes. Make sure to put the power tubes back in their original spots.

The good news is that changing the two tubes will take only about one minute. If you want to try them one at a time, it will take longer, since you'll have to start the amp up to see what difference changing one makes.

 

[Tuna141]

Also keep in mind that the tubes are "keyed" so they can only be plugged-in in the correct orientation. So, never force a tube in or you may damage its pins. Just rotate the tube until the pins on the tube line up with the pins on the tube socket.

 

[bird_droppings]

I bought this from the Mesa Boogie store in Hollywood, so I called them up this morning and talked it over with them. They suggest it may also be a problem with the reverb tank. They asked me to unplug the RCA connections and try it again. If the noise goes away, it's the tank. If it stays, it's the tube.

And if it's a tube, they confirmed that it's V4 or V5 just as you told me.

That's my project for tonight.

Thanks for the help!