Hello Les Jones !
You were right. I investigated this matter about an hour ago because I, too, believed the base current was too high and the transistor, saturated. So I changed R3 and R4 to both 47kOhm, and good news : now my AC signal shows up on the base ! I measured U_base = 2.6V DC +- 0.3V AC (x10 probe, so... 26VDC + 3VAC? Strange :/ )
Also I made a mistake regarding the input decoupling capa : it is 100nF and not 10uF as shown on the graph. Anyway, signal flows through.
Now the issue is, there is close to no power on the output. Did I choose my transistor wrong? (BD135, gain of 25 to 250 according to datasheet). Should I review the circuit design, and if so, how?
New measures : The voltages (DC coupling, x10 probe) were 3.8V DC +-0.15V DC at the collector, right between the transistor and the outpout capacitor. Why such a small variaton? I'm surprised because those tensions were measured with the X10 probe, that would mean I had 38VDC +-15VAC on my probing point? surprising.. How would you explain this, you, experienced members?
Best regards,
Benjamin