I tried to bias my old Marshall tubes in my Ma50C. So I could get them at 53mA and not at the recommended 35mA to 40mA. I put some NOS siemens EL34 tubes in there and biassing at 35mA was piece of cake.
On the feet of these Marshall tubes I read 49mA 8/37. Does that mean they were once biassed at 49 mA?
Wich surprises me?
I changed out the Marshall tubes for the Siemens. Are these Marshall tubes toast? Or is it ok for them to be biassed so out of spec? They redplated at 70mA. But at 53mA they did sound allright and did not redplate....