I powered up my Ampeg PF500 today and all looked normal, but I got no sound. Checked everything: cords, inputs, etc., nothing. I turned it off and then on again. Nothing. Then I waited a few more minutes, turned it on--and it was fine! Tried again a few hours later and the same thing happened. Took two "start-ups" and it worked fine. I haven't had any trouble in the over two years since I bought it, though I know all about the threads claiming otherwise. I'm sure I am out of warranty, so I guess I have to go amp hunting.