i've got a max jr (212 nr) and i'm pretty sure i've got a dead preamp tube. no sound coming from the amp, i put new power tubes is, tried diff guitars, and cables too - still nothing. if i'm looking at the back of the combo the preamp tube just to the right of the power tubes isn't lighting up. two questions - 1. what position is that tube? (v1?,), 2. what do you suggest i put in its place? i pulled the suspect tube and it's a sovtek 12ax7lps. any advice is appreciated!