There's only so much testing you can do before you have to bite the bullet and plug it in.
There are some detailed test plans but frankly, I couldn't be bothered with all that. I was keen to see if my amp worked. I did at least take the precaution of powering up for the first time with no valves.
Added all valves, powered main switch.
All valves glowing nicely. Waited a couple of minutes.
Moved standby switch to "on".
After powering down and unplugging the amp I put it back on the bench and looked for any wiring problems. After about two minutes of staring I saw what I'd missed - the ground wire for the cap can wasn't connected to the star ground, it was just curled under the turret board. Whoops! Stripped, tinned and soldered then time for a retest.
Right. Time for the signal test. Plugged guitar into normal channel, edged up volume carefully...
Bollocks. No time for any further investigation so powered down amp. Paranoia sets in. Could be a dodgy valve (can be eliminated by swapping them round) or could be something more serious - like the most expensive component of the amp, the output transformer, which can't even be replaced as the boutique maker doesn't make them anymore...