reverb self crashing

[Searing]

When my amp is just sitting there the reverb crashes ever so slightly, not loud or anything.  There is no vibrations?  Any thoughts?  Thanks!

Chris

[rafe]

Do you live in California? Earthquake? Mine has done that on a wood framed floor that wasn't stiff enough
when I'd get to moving about the reverb would crash......

[phsyconoodler]

Microphonic tube.

[Searing]

No earthquakes, although it is on a hardwood floor.

I replaced the tubes and tapped on them, did not seem microphonic, the reverb still crashed.  Tubes was my first thought.  Perhaps there is something going on in the tube that is causing this?  I will swap even more to compare.

[phsyconoodler]

Did you check the reverb springs in the tank?If they are flopping loosely they will crash a lot.How old is the tank?

  Also,is it in a bag and does it have a cardboard shield on the bottom?If it's just sitting in the cabinet with no bag or cardboard it will be set off by the vibrations on the floor.
 Try lifting if off the floor on a piece of carpet or a chair and see what happens.

[tubesornothing]

Tape cardboard to the bottom.  Put a strip of 1/2" thick weather stripping on the top.  Put it loosley in a tank bag. Screw it down through the bag, but not through the tank.

[RicharD]

Could it be a little static pop/crackle on the input side?  I knew an old Fender that for the first 5 minutes it was on, the reverb made some fairly serious noise.  Once it got hot, it stopped.  Never could find the problem.  I think it might have been the infamous conductive fish paper.  Only the shadow knows.

[Dave]

Yeah, if the plate load resistor is crackling on the 12AT7 (or whatever else might be causing it to crackle) that would cause the reverb to "crash".

Dave