Bad Buzzing in SF Bandmaster Reverb

[Blues Lyne]

I have a SF Bandmaster Reverb that was Blackfaced about 12-13 years ago. Both channels are connected to the reverb, so they are in phase. I use an ABY box to switch between the two channels. It also has a Vari-Watt installed.

Lately it's buzzing really bad, but the volume of the buzz will fluctuate. Some days it's better than others. Sometimes it will change from one minute to the next. If I turn both volumes off, the buzz stops. If I have nothing plugged into the amp the buzz stops. It buzzes if anything it plugged into the amp. It's not buzz from my guitar. It does it even if the pedal board is muted (Boss tuner is the last pedal on the board and it has a mute function). It buzzes even if a calbe is plugged in, but not connected to my board or guitar. It's worse If I plug into both channels. It doesn't change depending on whether I'm touching the strings of the guitar, like some grounding issues cause. One night it seemed like it was worse if the reverb was on, but that hasn't always been the case. It seems like the switches on the ab box and my pedals tend to pop more than they used to, but that could be unrelated.

I am running the volume around 7 with the Vari-Watt turned down, but this seems like more buzz than I should get. This is buzz, not the usual white noise.

My first thought was caps, since it's been almost 15 years since it was recapped. But, if it was filter caps, would it stop if nothing was plugged into the amp, or if the volumes were turned down?

Anyway, anythoughts on where to look would be appreciated. Thanks.

[Mutronics]

Ground loops?
Does it hum if you plug a guitar straight into one channel?

scx

[Blues Lyne]

Yes, it buzzes with just guitar>cable> amp, or even just a cable into the amp. basically anytime there is something plugged into either channel, and the volumes are turned up. I've tried several different cables, and while it was worse with one of them, it was there with all of them. We tried pluggin it into a different circuit and it still buzzed.

[booj]

Maybe you've lost a ground connection, or have a loose input jack or control?

[Mutronics]

Safari just crashed (again and lost my whole response!), grrr.
Do you get the hum when plugged into either Hi or Lo jacks?
Is it a low level or guitar-swamping level?
If the latter then I tend to agree with booj.
Check that the jacks ground connection to the chassis (is that where the ground ref for the jacks comes from?) is good and we can work from there.

scx

[Blues Lyne]

This is so wierd. At one point the buzz seemed to go away if I unplugged the reverb cables, but then came back. I tried it with just guitar-cable-amp and it buzzed. But last night, it only buzzed if it was connected to my pedal board. I unplugged my onespot and all the buzzing stopped. I'll have to bring my other amps in and try the onespot with them, because I didn't get any buzz from it when I was using my other amps previously.

I plugged in another power supply and the buzzing was gone, though there was more hum or white noise than when the pedal board wasn't plugged in. I started to unplug the power from all of my pedals to see what happened if they were all run from batteries, but realized I'd have to take the board apart to get some of the plugs out. And, some of the pedals didn't have batteries in, so I'd have to get some batteries and pretty much completely disassemble the board. So, I plugged everything back in, and now I'm getting a lot of hiss from several of the pedals that were totally quiet before.

I'll experiment with using my pedal board with different amps tomorrow at rehearsal.