That depends. What is the B+ voltage? If the supply is high, like 490v, too low a bias can raise the B+ up a little. That's not good if the filter caps are rated at 500v. Double check the B+. You may need to change a resistor on the bias supply to get the pot in range. Also 10watt wirewound? 1Watt should be enough. If you don't want to do all that, just crank up the amp and wail on it for 5-10 minutes. watch the power tubes as you do this, if one or both start to glow in the center that's the tube burning up, lower the bias.