Hi there, I successfully built a 5e3 Deluxe Micro by RobRob and tried to follow it up with a Blackvibe build. All seemed well as the build seemed to work but the amp seems to have a problem specifically with the power tube (12AU7) or the socket or something around there. When I turn it on, it takes maybe 5 min to warm up enough to get enough headroom. Prior to that it sounds almost silent and you can coax out some distorted sounds by cranking the master volume and turning up the preamp volume. After 5 min, it sounds fine. But after playing for maybe 20 min or so, something happens to the 12AU7. The output goes down a lot, and you can crank the master to around 7-9 and it'll make noise, but very quiet. And the tube while it still works in other amps, it's not the same. I've put in a new 12AU7 and the same situation repeats itself. I've gone through 3 tubes so far. I confirmed without the power tube, the voltages in B+1, B+2, B+3 are what I expect them to be. When I put in the power tube instead of reading 395V DC at B+1 it seems to be more at 345V DC. Also I thought there should be no DC voltage at the grids (pin 2 and 7) on V2 and V3 (phase inverter and power tube) but I'm getting around 40V DC there. I thought that meant I had leaky coupling caps so I replaced those with new ones but the old ones read fine and no change. I also re-soldered connections to the power tube. At this point, I don't really suspect any components on the turret board so much as connections to the power tube socket or the socket itself. My problem with the 5e3 Deluxe Micro build was around heater wiring and soldering. This time seems to be fine, but soldering to tube sockets seems to be where I run into the most trouble. If anyone has any ideas what might be wrong or any tests to confirm / deny any possible issues, I'd appreciate it. Thanks for reading.