You build something, it looks scruffy with the component layout, a few instability problems sorted by a 100 pF cap (anode hf bypass) but at the end it all works and sounds OK.
So you do a board layout, get feedback and change a few things. Get the boards made, go bigger with the metalwork to act as a bigger heat-sink, spread the valves further away from the transformer so it does not get direct heat etc.
You wire components up, add the output transformer, get the valve bases connected and do a temp connection from the power supply and to the speaker, have bits of audio cable from the PC to the input. You then power it up and listen to a song or two!
So, why the hell should I be so surprised when it appears to work? It's to late to start with the scope and multimeter to check every voltage tonight to see if it meets previous specs, but wondering why I have to think it would be a failure?
I can only guess apprehension after the time and effort.
Sorry for the temp connections, with the heater wires I will be trying some hot glue to anchor them to the board.
The chassis is approx 244 x 150 x 40mm I need to contemplate a heat-sink from the aluminium valve collar to the chassis, the valve holder on this one is proud of the chassis so the TT15 base does not sit on the chassis to dissipate any heat and the aluminium collar soon gets very hot. I remember a metal clip on the aircraft set between chassis and valve base, but I assumed it would be to keep the valve in place, the aircraft radio also had forced air cooling!
Adrian