baudouin0,
Good catch!
30% UL.
Another thing I notice about that circuit is:
It puts the screens Quiescent DCV at 75% of the UL Tap Quiescent DCV.
Suppose the UL tap is at 400V. In that case, the screens are at 300V quiescent.
That is Lots easier on the screens in terms of the maximum screen current during the time when the plate is going low voltage on its way toward the cathode.
At 30% UL, If the plate goes to 50V, the change is 350V. 30% of 350V = 105V, that puts the screen at 300V - 105V = 195V
Look at the curves to find the screen current for Vp = 50V, Vg = 0V, and Vs = 195V.
Not too much screen current.
At 40% UL, If the plate goes to 50V, the change is 350V. 40% of 350V = 140V, that puts the screen at 400V - 140V = 260V
Look at the curves to find the screen current for Vp = 50V, Vg = 0V, and Vs = 260V.
Lots more screen current.
How is that for a little bit more analysis?