Quote from: J M Fahey on January 30, 2010, 01:09:29 PMI did replace the rubber feet,however I also tightened the reverb pan screws down tight,I'll have to loosen them.
Then, as Enzo guessed correctly, your reverb sprongs are feeding back because the speaker makes them vibrate.
Manufacturers use various "medicines" to avoid it, none of them very effective, but if you use many ....
Obviously that defect didn't exist when the amp was new.
Manufacturers do:
1) the spring sub-chassis "floats" inside a larger metal box, suspended by 4 tiny springs. If one or more stretch or unfasten and the subchassis touches the box: it feedbacks.
2) that box is held to the cabinet side or bottom by 4 screws that go through soft rubber rings, If they are old they crystallize or become a sticky goo; replace them.
The screws are *not* tightened, they are loose and let the box bove around a little.
A typical un-experienced owner tightens them. Mistake !!.
3) Fenders wrap the box in cotton-like padding, and stuff that into a Tolex envelope, lightly fastened to the bttom of the amp.
To avoid the cotton touching the reverb springs, they close the box with a piece of cardboard.
I see you get the point: "float" or decouple mechanicaly the reverb tank from the vibrating cabinet.
Some players, Paul Young and Dick Dale come to mind, mount their reverb tanks in another enclosure *away* from the main amp, even in another room or under the stage.