trinityamps.com

When I begin powering on and begin testing with no tubes in place, all is well when the Power Switch is on, but Standby Switch is off - voltages where they are supposed to be at all check points. When I install a rectifier tube, power on and hit the standby switch, the tube turns quickly hot red, the fuse blows, & the tube is shot. I've checked the wiring numerous times, run continuity tests, and can't seem to find a obvious short. I've gone through 3 rectifier tubes at $23 a pop.

Any ideas on what might be the problem? Or how can better diagnose the problem?

This is my second Tweed build from a Trinity kit. The first one works well.

It's concerning that your rectifier tube is overheating and blowing the fuse when you switch to standby.
Always unplug the amplifier before working on it.
Double-check your wiring for any shorts or loose connections before powering on.
Replace blown fuses with the correct type and rating.