So I bought a Bias Rite recently along with a new set of NOS RCA 6L6s for my 67 Vibrolux. When I hook the Bias Rite up, I get 427 for plate voltage but my tubes are running at 33/35. From talking with friends and referencing online docs, it appears that, at that plate voltage, I should be biasing it so that they are in the high 50s or low 60s. So I turned the bias pot all the way up - and it moved the tubes from 33/35 to 34/36. Ugh - it was barely a half turn and then I'd turned it all the way up. I then swapped tubes to a new set of Ruby 6L6s - they measured roughly the same. I then swapped one of the tubes to another old RCA that I have - it measured at 35. By this point, I know that it isn't my tubes. What would you suggest? Someone suggested I change out to a new bias pot. I can do that - I just don't want to do that unless I need to. I could take it to a tech but I'd hate to spend $75-$150 if it's something as simple as replacing a resistor or replacing a single pot. Stuff I think may be important: The amp sounds kinda cold biased As far as I can tell, all the caps/guts are original with the only exception being the 3-prong power cable. All other tubes are original to the amp (or are NOS possibly) Thank you!