Before plugging in the tubes I tightened them and cleaned them as best as I could but I’m still getting this discrepancy. Any thoughts on what could be causing it? Bad socket? Transformer? All 4 plate voltages are the same.
It doesn’t seem to affect the sound but I lost a tube in that socket prior to adding the auto-bias. I also checked resistances on the cathode circuits prior to the AB and found no differences in any of the sockets.