Deluxe Reverb: Reverb buzz?

[Rhodesplyr]

I've just done a little work on a Deluxe Reverb Reissue, and I noticed that the reverb is pretty noisy. The owner doesn't really use reverb much, so he didn't want me to spend a lot of time working on it.

The major problem was a bad RCA connector at the output of the reverb tank, but even after replacing that cable, there's a buzz that increases with the reverb volume setting. From the sound, it has to be a grounding issue, but the main amp chassis and reverb tank body are connected via the return cable shield. And the reverb drive cable is isolated from ground at the tank, so there doesn't appear to be a loop.

With the reverb tank disconnected, the buzz disappears. It's not the reverb recovery AX7.

Is this just a noisy reverb circuit, or is there something I haven't found?

[Rhodesplyr]

What I found: the buzz disappears if I plug in the Reverb/Tremolo footswitch. Not sure why yet. On other Fender amps I've worked on, you could use reverb without the footswitch plugged in.

[Enzo]

Oh well, I was gonna suggest unplugging the FS. The reverb FS is nothing more than a shielded cable connected to the return, and the FS grounds it off to kill the reverb. Of course the jack and cable are connected right to the reverb signal path then.

[riz]

Someone actually told me once that it was "an old studio trick" to plug in the pedal to reduce reverb buzz/hum... that would be on the older amps, of course.

[JoeM]

My DRRI does something similar. The weird thing is the physical orientation of the tank can change or eliminate the buzz, like a ground wire makes connection if the tank is orientated in a particular place. I've considered trying the tank from my 70's SFSR to see what happens. I dont have the FS attached, I'll try that and see it the buzz stops.

[Enzo]

Keep the OUTPUT end of the reverb pan as far from the power transformer as possible. The little pickup transducer can also pick up the transformer field. SOme pans have a metal plate covering the botom opening, or at least part of it, as a shield. Sometimes installing the pan facing the other way does this.

[Rhodesplyr]

Keep the OUTPUT end of the reverb pan as far from the power transformer as possible. The little pickup transducer can also pick up the transformer field. SOme pans have a metal plate covering the botom opening, or at least part of it, as a shield. Sometimes installing the pan facing the other way does this.

In fact, when I was replacing the cable, I noticed that the output end of the reverb pan was turned towards the power transformer end of the amp, so I turned it around. This did decrease noise.

When I built my replica Farfisa power supply/spring reverb, I experimented with different reverb pan/power transformer orientations to find the one that allowed the least noise coupling. It's not always easy to predict.