Admin Post Just brought home a Fender Fudge Brownie PRRI. Way different sounding than the "regular" model with the ceramic speaker. Problem is, if I turn the reverb up past 2.5 or so, huge feedback roars out of the amp, even with nothing plugged in. I've had a ton of Fender amps, both vintage and reissue, and have never had this problem. Before I lug the amp back to the store (50 mile round trip) I'd like to ask the collective wisdom of the group here. My first guess is that it's a pre-amp tube. Which one should I try swapping first? If that doesn't work, any other guesses as to what the problem may be? Thanks for any help.