Looks like that 5U4G rectifier tube is about to launch itself into low earth orbit.... This isn't one of my experiments "gone wrong", someone just sent me this picture "what's wrong with this picture"...

The sharp-eyed obsserver would also notice that metal 6L6s are inserted into sockets marked for "6L6G" but that woldn't cause this impending meltdown, as they are basically interchangeable.