Hyllej,
The fact that all the tube voltages are correct is a good sign that the tube circuitry is functioning properly. The first thing to do is to tighten the tube socket. To do this you just need to get some sort of sharp, pointy tool and gently pry the tube socket contacts closer together to help them grip the tube pins better. Sometimes they get spread a little to far apart in the “loosening the tube socket” step, and they don’t make good contact with the tube pins.
If this doesn’t work then you probably need to re-flow (re-solder) the solder joints again. I know it’s a pain, but the fact that you had one bad solder joint is a sign that other’s could be bad as well. At first, just re-flow the resistors from the top (component side) of the board so you don’t have to take out the PCB. If that doesn’t work then you’ll have to take out the board and check really closely for solder bridges (shorts) and re-flow the capacitors and other components that you weren’t able to get to from the top of the board.
You really shouldn’t turn on your amp without a load (speaker) attached. It’s really bad for the tube. So make sure the speaker is plugged in when you test it. It’s not uncommon for properly working tube amps to behave like that when they don’t have the speaker plugged in…so i’m not worried about the buzzing with no load. The problem is that the signal is not making it through somehow. We’ll get it sorted out one way or another.
-Brach