RV 50 combo

[douguitar]

Hey - new guy Doug here...Love my RV-50 combo, but have been having what appears to be a severe microphonic problem. Certain frequencies (f sharp in particular) cause a rattling hissing noise. I've replaced tubes and tapped around, helped a little. When I tap the choke transformer, it set the sound up and at certain volumes (higher) gets downright annoying. Anyone else out there with a combo have any similar problem? Any suggestions? I've also tried rubber mounting bushings on the choke transformer and a couple of the tube retainer clips, but it's still there. Plugging in to an extension cabinet with the internal speakers disconnected solves the problem, so it's definitely vibration induced. I hate to use this thing just for a head!
Anyone?

[Les Paul Lover]

Sorry mate, I'm of no help, but I've noticed how my radiators pipes will vibrate more on F#, G & D than other notes.

Dunno what it is about those notes vibrations patterns that pleases my central heating so much.

Hope you get it sorted soon. A good thing you have another speaker cabinet at hand!

[llldavid]

no help either sry if it makes you feel better the song im workin on is in the key of F#

[greyvents]

Hi Doug,

I had this prob with my Cornford combo. Certain frequencies caused a rattling / vibrating / buzzing noise.

What I ended up doing after numerous suggestions from the guys on here, was to swap out my power tubes. Cornford sent a new pair. Thankfully this worked for me - no more rattle.

One of the original tubes, when shaken, made this weird metallic sound like something had come loose.

So maybe try swapping tubes?

[riffmonster]

Hi

1) Sounds to me like a speaker problem - if swapping tubes didn't solve it but a different cab did?

Had a problem with a Bass combo recently, weird buzzing noise on certain notes and eq setting. Tried all sorts of things, eventually solved by putting in a new speaker.

2) Might be worth posting on the technical forum

[greyvents]

oops, sorry missed the bit where you said you'd already tried swapping out the tubes.

[irish_admiral]

Hi Doug,

If swapping to an extension cab made the rattle go away, I think you've solved your problem there.

Unfortunately, part of the mojo of combos is that they tend to have all the little rings caused by internal vibrations. Not much you can do about it other than your solution above. You can try tightening all the fixings - just normally - and you can get high-heat resistant O-rings to go round valves to stop them ringing out if that's what's doing it, but other than that, like it or lump it...!