Re: New Tube Amp Problem
Surprised no one suggested a dead or dirty input socket - You've found the source of the issue it sounds like (which is great), but the general rule is to check the simple/obvious things first before opening the amp up and tinkering. More often that not amp issues are the result of very simple problems - tubes being the most common! I've had an amp go dead on me, only to come back alive after I sprayed a little contact cleaner in the input socket and plugged a cable in and out a few times. I also wrap a small piece of sandpaper over a small pencil and use that to take any corrosion or gunk off the socket as well. Keeps them going without having to replace.
As for tubes, if a tube is a milky white colour, doesn't light up at all (which can be hard to see sometimes), or has visible damage (cracks, broken, etc) then it needs replacing.
Let us know how you go with the replacement tube though, hope it solves it for you!