Here are some approximate measurement numbers. I have no test yet to replace the D5 and D6
Pre stage drive Transistor KSA992FBU (PNP)
Q1, E = 0.7V, C = 42V, B = 0.15V
Q3, E = 0.15V, C = 42V, B = 0.9V
Q2, E = 1.5V, C = 39V, B = 0.9V
Q4, E = 1.5V, C = 43V, B = 10.0V
Varistor
D5, + 2.3V (across)...