A frequency modulated signal is available at the output of theMixer/Amplifier block at tp34. Check that it is present by monitoring this
waveform. The frequency deviation is quite small so, if you have an X-
expansion control on your oscilloscope, you can adjust the timebase to
display about 20 complete cycles. Expand up the rightmost cycles on the
display. There should be a slight uncertainty in the positions of these cycles,
indicating that the sinewave at tp34 is being frequency modulated.