The Boogie Board

If I change the 2 6L6's from say "red" to "green". Do I need to re-bias the amp to accommodate the new color code ?

Also. I know the F-50 has set bias. What is it ? and should I get the bias checked on the reg to make sure its still at factory setting.

Thanks.

If you are using Mesa branded tubes you should be good to go. Just plug them in. If you have lingering doubts a tech could probably check that the amp negative bias voltage is still where it should be. It would take a total of about 5-10 minutes on the bench so it should not be that expensive. I am rehabilitating a 50 Caliber at the moment built in 1989. Had to change out a few of the carbon comp resistors in the bias supply as they had drifted a little. Negative bias voltage was off a little bit. Put metal oxides in this time so that section of the amp should be good for many more years.