Problems with Rivera TBR-2SL Tube Head

[vaijem777]

Ok...I haven't run into too many tube amp problems that I've not been able to remedy, but I'm about ready to toss my Rivera out the window!

I had (2) Rivera TBR stereo rackmounted heads: a TBR-1SL (60W per side) and a TBR-2SL (160W per side). I had the 1SL in my rack because I got it first and it was too much of a pain to swap them out, etc. Anyway, the amps are identical with the singular exception of the power. I grew to prefer the sound of the 2SL though- much meatier, more power, etc. So, I sold the 1SL and rebuilt my setup around the 2SL.

That's where the trouble started. Everything was connected exactly as it was with the original setup. The amp was given a fresh set of JJ tubes (power and preamp). I checked with Rivera, and they said that there should be no problems popping new tubes in, as long as they were the same types (EL34s).

The problem is that I'm getting some pretty nasty buzzing on the gain channel. I've tried the following:

-removing EVERYTHING else from the equation, and gone from guitar, to amp, to cabinet. Still buzzing.
-I've tried (3) seperate sets of new tubes (Svetlana, JJ & Groove Tubes)
-All new cables (both guitar/FX cables and speaker cables.)
-Tried both Pentode & Triode modes, and with both power amps
-I've even tried different guitars and different cabinets

It's driving me nuts! The TBR-1SL was completely silent, and with the same model of JJ tubes, and I've had great luck with JJs in the past. I'm honestly at a loss here. I've got a backup rig, but...it's just not the same. The noise gate on my G-Major helps cover the noise up for the most part, but...it really bugs me because it shouldn't even be there at all. I'd expect SOME hum, since it is a fairly high-gain amp. But, what I'm getting is definitely not normal.

I'll most likely end up trying to get ahold of Paul Rivera Sr. or Jr., since they've both been very helpful in the past. But, they've been extremely difficult to reach lately, so...does anybody have any ideas/suggestions? Is it possible that the amp needs rebiased after all? I've not had to rebias any of the dozens of amps I've had before, including the other TBR. But...if that might help it may need to be done.

Thanks in advance for any and all input!
Chris

[microdmitry]

Does it buzz without G-Major connected?
Without anything connected to its input?

Sounds like a grounding problem (ground loop inside or outside the amp) or a bad capacitor to me.

[vaijem777]

Yup...I still get the buzzing with nothing at all connected to the amp but a guitar and a cabinet. I've tried all (3) settings on the ground switch, but there's no change.

[Gresh]

How about swapping out the preamp tubes?

Is it buzzing or hissing that you hear?

[vaijem777]

I've tried swapping out ALL of the tubes- preamp and power. I've had (3) full sets, all different manufancturers, and from different sources.

It's a definite "buzz"- not the normal hiss. It's infuriating!

[ATDVSBL]

Does the "buzz" characteristic change in frequency or level as the output load changes?

[vaijem777]

When the volume goes up, the buzz simply gets louder. But, that's the only change in the frequency or overall character of the sound at all.