Alinco DJ-X3, Service Manual, Page: 5 / 35

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6. Audio
FM/AM/WFM
The audio output signal for receiving FM/WFM and AM is switched at IC9. The
output audio signal is input to pin 1 of IC13 of stereo multiplex demodulator
through AF amplifier IC17. When the input audio signal doesn't have a pilot
signal, each audio signal is output from pin 9 and pin 10 to pin 1 and pin 16 of
the audio amplifier IC14 equipped with the electronic volume. After the volume
is adjusted, the signal is output from pin 7 and pin 10 to drive the speaker, etc.
When the input signal has a pilot signal, each audio signal is output; L side
signal is output from pin 9, and R side signal is output from pin 10.
Then the signals are input to the audio amplifier IC 14 equipped with electronic
volume; L side signal is input to pin 1 and R side signal is input to pin 16. After
adjusting the volume the signals are output; the L side from pin 7 and the R side
from pin 10 to drive the speaker, etc.
7. VCO
The 1st Local
VCO for the 1st local consists of the Colpitts oscillator. D15, D16 and L4
determine the frequency, and the signal is oscillated at the transistor Q9. The
oscillated signal is supplied to pin 2 of PLL-IC1 passing through the buffer
amplifier Q11 and Q10.
The 2nd Local
VCO for the 2nd local consists of the Colpitts oscillator. D20, D21 and L15
determine the frequency, and the signal is oscillated at the transistor Q19. The
oscillated signal is supplied to pin 19 of PLL-IC1 passing through the buffer
amplifier Q20.
8. PLL
PLL-IC1 is used to control the oscillating frequency of VCO. IC1 is controlled by
the serial control signal sent from the microprocessor IC7. The reference frequency
of 12.8 MHz is generated by oscillating the crystal oscillator X1 inside
the circuit.
The 1st Local
IC1 compares the frequency gained by dividing the signal added to pin 2 of IC1
by the control signal from IC7 with the frequency gained by dividing the
reference frequency of 12.8 MHz inside IC1. When the phase difference is
found as a result of phase comparison, the pulse signal is output from the
charge pump output of pin 8 of IC1, then the signal is converted into the DC
voltage at the active filter Q13 and Q14 and added to the cathode side of VCO