I noticed when turning on the crack the 6080 tube starts glowing blue/purple ish and then the glow quickly goes away. Is this normal? all of the ohm resistance checks and voltage checks seem to be pretty close to the ones stated in the manual and the amp works and sounds perfectly fine. I recorded a video of the glow and uploaded it to youtube but i can't seem to post the link. Here's a picture (sorry for the crappy quality).