[old_tv_nut]

It is ususal design process in transistor circuits to design for proper operation whenever the transistor current gain (beta) is above a certain minimum.

Looking at Q801, you see that the peak to peak waveform on the base is twice the size of the DC voltage, so this stage is being overdriven to clip the AC waveform. The DC bias uses feedback from the collector load. Given all this, it's likely that any general purpose transistor with a beta of say 100 or greater would work.