Just to clarify: ?The FET on the small board is the driver (Q504). ?The pre-drivers are Q101, Q102.?The first adjustment in section 4-4 sets the Driver idle bias. ?The remaining steps adjust the PA idle bias.
I would check the bias voltage (ID3V) at R501 and at the gate of Q501 (VHF PA) to see if it varies when you adjust it. ?If it does not, then there may be a problem with the bias circuit. ?Otherwise, Q501 may be defective.
I haven't seen your symptom. ?The two Q501's that I've replaced both had low output, but that's a small sample.
Steve, W3AHL
Steve W3AHL