help with noise... Fender Supersonic 60... soundclip...

[ruger9]

Soundcloud below.

Prelude:
It only happens when the amp is LOUD, like gigging-without-micing loud.
It has happened with 2 different speakers, one of which is brand new.
It has happened with 2 sets of power tubes, and 3 sets of preamp tubes.

I think I have eliminated those, meaning it's something inside. It's the static-y sound you hear on the soundclip. And I couldn't get the amp to do it that day, but it has in the past gone into, for lack of a better word, oscillation... that static-y noise seems to be a precursor to the amp going into full blown "weeeeeeeeeeeee" high-pitched noise, and the only way to stop it is to put the amp on standby for a few seconds.

It's been with a "Fender Authorized Tech" for 3 weeks.... he said "I can't find anything wrong, and I can't turn the amp up loud enough in this room for it to make that noise".

Anyone have any ideas? I need this amp to be reliable- it's my gigging amp (a Supersonic 60, the 2nd generation)

Soundcloud:
https://soundcloud.com/ruger9/amp-noise

[Justin Thomas]

I vote bad connection somewhere. How comfortable are you opening up the amp? Because to me it seems to be frequency dependent. You'd want to have someone playing the frequency steadily or use a looper & chopstick various connections.

One idea: check your input jacks. Wiggle the cable in the jack while someone plays & see if that sets anything off.

If the tech can't turn it up loud enough in tjmge room then time for a bigger room! If you get him that recording then he should get an idea. Then it's dummy-load-&-scope time, I think...

Justin

[Mick Bailey]

Two things spring to mind here - either noise levels vibrating something, or something breaking down due to being stressed electrically. The scenario is fairly common where 'something' only happens at high volume and sometimes after a period of prolonged playing. In a workshop environment it's inconvenient and unpleasant to have to crank an amp while working on it and most people in the repair business have their own techniques to avoid this.

Chopsticking is my first approach, but beyond that I use a handheld engraving machine that has a plastic rod and rubber tip especially for amp work. It operates like a tattoo machine - basically just a solenoid with an adjustable stroke/intensity. I can dial up the Richter scale and apply it to boards, connectors, cables or the chassis. It rarely fails to reveal a mechanical problem. To stress the amp electrically, I use a signal generator, dummy load and scope - sometimes in combination with vibration.

I usually try to divide the problem to narrow the fault down to preamp or power amp. By injecting a signal into the 'power amp in socket' this bypasses the preamp. If that's OK I shift my attention to the preamp.

[ruger9]

Thanks for the replies. Yes, I've lost confidence in the tech at this point, "Fender Authorized" or not. I'll take it to the local guy (really the ONLY other local guy) who's been doing since I was in hair bands in the late 80s lol. That's where everybody goes. I just know he'll keep it for awhile, and I was looking to avoid that.

[Jazz P Bass]

I had a Super amp with a similar issue.

There is a tube socket all by itself mounted slightly under the main board.
There was a grid wire that was never soldered at the factory.

It took the amp being cranked to jostle the wire enough to make a bad connection.

Moral of the story.
"It could be anything."