Nomad 100 2x12 combo issues...HELP !

[prs1999]

I found a killer (looks is **** mint) Nomad 100 combo w/the graphic EO for a cheap price,BUT.... When the gain on ch.2 and 3 is put anywhere above2 to 3 oclock the thing makes an un-godly "worbleing"( fluttering,pulsating) sound. the more gain you add,the worse it gets.Sounds like a tremlo effect on a medium speed.

I tried swapping preamp tubes around,but it still does this.
Now in clean mode and clean mode pushed,it does not make this nosie even when the gain is maxed.

I doubt this to be a power tube issue as the amp sound beautiful anywhere else but super high gain settings. Also the master volume cuts out when near maxed out (thats a new pot oissues..no biggy).
But,I'm wondering to buy this,then find out its a simple fix or...$$$$ is needed to get her working and sounding like new.
Anyone got an idea???
Thanks

 

[prs1999]

By the way,this amp was purchased by the owner in 2001 and has never had new tubes put in,but he is a bedroom player and told me this amp has does this noise since new and he just dealt with it.
I still cant see it being a tube issue.....I smacked the 6L6's pretty good and they dont make a noise.

 

[FEUD]

Hi

I had (possibly!) the same problem a while back, and it turned out to be the effects in the effects loop - are you running anything through there?

 

[prs1999]

no..there was no F/X's in the loop...and I didnt buy the amp..yet.
still trying to figure out why its making that noise.
anyone else got a clue?

 

[dennq45]

Its called motorboating.. You may have a bad or an unsoldered capacitor.

 

[prs1999]

LOL..thats about the noise it makes.."motorboating".
Thanks,sounds like a cheap enough fix.