When you open the top and look at the main board, the bias pots, which are located on the rear left area of the main board are easy to spot because they are the only variable pots on the board, and they are each marked the this text: BIAS.
We normally start a new unit in QC with the pots set in the halfway position, but that’s unnecessary when replacing tubes. You can simply start with the existing position and tweak accordingly, or go back to the mid-point and adjust from there.
We set the bias according to the procedure attached.
Dave
2902Bias.pdf (50.2 KB)