I bought a used Ghia head a couple months ago. I finally got a cabinet. I played it a couple hours last night though tha cab sounded purty good. I bought some NOS tubes that came today. I put the tubes in &...... It made a deep bassy humming sound ..I could still hear the guitar then it just died. The light on the front of the amp went out... no power at all. You think it's something to do with the tubes ..or just a coincidence that the amp died after putting the tubes in it?