I bought a used walkabout a couple of weeks ago off ebay. I have two problems that I would like your opinions on since I am a relative noob to bass amps (especially tube amps). 1. When I recieved the amp, I heard a rattling sound. I removed the cover and found a missing tube (left side tube looking at the front of the amp). The tube was rolling around under one of the boards. I talked to the guy I bought it from and he says he never opened the case and said that maybe the tube fell out of its seat in transport, but when I replaced it, the fit was way to tight for that to be the case. He also said that it worked perfectly when it was shipped. Can this amp run without that tube? 2. It wasn't happening at first, but now I hear a somewhat faint sound like a very small vacuum cleaner that comes and goes no matter what the volume knob is at. And, about every 10 minutes, the low E and low B will distort (this is at low volumes). What is going on? Could that tube have been damaged when rolling around? I know you guys have a wealth of experience and knowledge, do you have any thoughts on this?