I think it's time to replace my power tubes on my Rivera Quiana 212 since I saw a bright blue flash out of one of the tubes and heard some unusual crackling. Plus, the tubes are five years old. Since I've never done this before, I've been reading up on different methods of biasing, plate voltage, current, dissipation, etc. I have a few questions for those of you who've worked with a Rivera. 1) I purchased a Weber Bias Rite with the plate voltage option. Rivera recommends unplugging the speaker when biasing using their method. Do I leave the speaker plugged in with the Bias Rite? 2) It also seems that I need to turn both masters and volumes all the way down and leave the input jacks empty. Is this correct? 3) Do I have to remove the chassis cover to access the bias pot? Is there no external access hole? 4) In general, should the bias be turned all the way down when starting with a new set of tubes (in case they're significantly different from the previous set)? In that case, which way is all the way down? Clockwise? Counter-clockwise? 5) Lastly, I just want to double-check my methodology. It seems the rule of thumb is 60-70% plate dissipation. For a 30 Watt 6L6, I would need 42 mA at 430 Volts to get 60% power dissipation. Correct? 6) One more thing . . . any general safety rules for opening up the chassis? Anyone who can enlighten me, your help would be much appreciated. I want to make sure I have everything correct to prevent ruining a pair of $80 tubes.