Strange reverb noise

[NBlair930]

ThIs morning when cranking my 22 watt BFDR-inspired combo, i notice the reverb was making a short distorted 'boing' only on the lowest notes or low power chords. Not full on distortion of the fundamental sound coming out of the speaker, just a seconday short noise. It also started doing this with a wha pedal in the heel down position (also low notes). Any thoughts to cause? Cure?

 

[terrapin]

I had a similar problem once with my Juke Coda and Gary troubleshot it for a LONG time before we realized one of the springs in the tank had come off and was hanging loose in the tank. Only showed on low notes as a distorted after effect. I would look at the tank.