Icom IC-551D Instruction Manual page 43

010 ОМ. The voltage at the emitter of 010 becomes approximately 0.6V below the voltage at the
base of 010.
Thus the input voltage of regulator 1С7 is regulated at the total of the zener voltage
of D2 and the emitter voltage of Q10. When the input voltage of ІС? varies, the emitter voltage of
Q10 varies because the zener voltage is stable.
The variation in the voltage controls е
Бу
controlling the base current of Q9. Thus the input voltage of ІС? is regulated.
VCO UNIT
The VCO (Voltage-Controlled Oscillator) is a Colpitts circuit, using O1, and oscillates in the 40MHz
range. The oscillation frequency is controlled by a DC voltage which is supplied from the loop
inserted in parallel with the oscillation coil.
DRIVER UNIT
CLOCK PULSE GENERATOR AND UP/DOWN CONTROL CIRCUIT
UP/DOWN CONTROL CIRCUIT
SCHEMATIC DIAGRAM Ка Ki K2
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