Fizz at Certain Frequency's on Princeton Reverb

[Perkinsman]

I have an odd issue on a Princeton Reverb that I've never dealt with before. There's an unatural sound that occurs more prominently around certain frequencies, mostly around an A chord, which immediately made me suspect that something was loose in the cab. At first I thought it was a loose speaker on the baffle but tightening the nuts didn't help. I looked for other loose joints in the cab or even staples holding the cloth but couldn't find anything loose that might be causing the rattle/buzz/fizz sound. I thought I remember seeing a youtube video once about a similar problem but i can't find it now. Looking under the chassis for loose components didn't yield anything either. Most all of the ecaps have been replaced. Has anyone here experienced a similar problem or have suggestions?

[Enzo]

Isolate the problem. Disconnect the speaker in the amp and wire it up to some other speaker cab. Does it do it over there?

And a different ttest, remove teh amp chassis, but leave the chassis connected to the speaker in the cab. Does it still do it that way?

[Arbutt]

Hi. Ive done a few of these recently and turned out to be the power tubes, Replaced them cure the issue, I would check it with another speaker / cabinet to see if it the speaker as enzo says ,

Just as another point, I have had a fair few set of TAD ( Tube amp doctor) that have had this problem
6V6 and EL84
Mr A

[Perkinsman]

That's good to know about those tubes, luckily I have my local tube supplier who i know and trust and has good test gear. As far as the noise, isolating the problem as you both suggested was the key lesson to learn here. I could have bet my next paycheck the fizz/rattle noise was a loose part in the cab, my second guess was the possibility that the speaker was loose on the baffle, my third guess was a tube...but all the tubes tested strong. Using my Deluxe head to power the Princeton speaker cab and still having the problem, I knew it was the cab. I switched out the speaker and voila, no more fizz/rattle!

[g1]

Glad you solved it. But just to let you know, a rattling or squealing tube will test fine on a tube tester.

[Arbutt]

That's good to know about those tubes, luckily I have my local tube supplier who i know and trust and has good test gear. As far as the noise, isolating the problem as you both suggested was the key lesson to learn here. I could have bet my next paycheck the fizz/rattle noise was a loose part in the cab, my second guess was the possibility that the speaker was loose on the baffle, my third guess was a tube...but all the tubes tested strong. Using my Deluxe head to power the Princeton speaker cab and still having the problem, I knew it was the cab. I switched out the speaker and voila, no more fizz/rattle!

I have had the same issue with a new set of tubes, that on the tube tester worked perfectly, but in the amp there was a slight noise out the speaker at certain freq.
I changed the tubes for another new set, noise went away