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The detected signal output from the PLL IC (pin 2) is con-
verted into a DC voltage (lock voltage) at the loop filter and
then fed back to one of the VCO circuits (Q5521, D5521,
L5523).
The oscillated signal from the buffer amplifier (Q5601) is
also applied to the MAIN unit via the "M1LO" line as a 1st LO
signal after being amplified at LO (Q5602) and buffer
(Q5603) amplifiers or passed through the bandpass filter
(L5602–L5604, C5610–C5616).
4-3-3 2ND LO AND REFERENCE OSCILLATOR
CIRCUITS (PLL UNIT)
The reference oscillator (X5251) generates a 32.0 MHz fre-
quency for the DDS circuits as a system clock and for the LO
output. The oscillated signal is doubled at the doubler circuit
(Q5202) and the 64.0 MHz frequency is picked up at the
double tuned filter (L5203, L5204). The 64.0 MHz signal is
applied to the RF circuit via the "M2LO" line as a 2nd LO sig-
nal.
4-3-3 3RD LO CIRCUIT (PLL UNIT)
The DDS IC (IC5701) generates a 10-bit digital signal using
the 32 MHz system clock. The digital signal is converted into
an analog wave signal at the D/A converter (R5701–R5720).
The converted analog wave is passed through the low-pass
filter (L5781–L5783, C5781–C5785) and is then applied to
the MAIN unit as the 3rd LO signal (422.500 kHz) via the
attenuator (R5781–R5783).
• PLL CIRCUIT
PLL IC (IC5401)
Programmable
Programmable
divider
DDS IC
(IC5101)
Programmable
Phase
divider
detector
Programmable
divider
D/A
convertor
MAIN loop VCO
Phase
Loop filter
detector
Q5604
LO
divider
Loop filter
Reference loop VCO
Q5301, D5301
AMP.
Q5351
DDS
Reference OSC. (32 MHz)
X5251; [USA], [CAN]
X5281; [OTH]
4-4 FRONT UNIT (RC-26)
4-4-1 LCD CIRCUIT (DISPLAY AND CONNECT
BOARDS)
The LCD (CONNECT board; DS8920) is controlled by the
LCD driver (CONNECT board; IC8940) via the drive signals
(CL1, RES, CS, RS, WR, RD, DB0–DB7) from the display
board.
The
(DS8300–DS8304). The LEDs are controlled by dimmer
(Q8300, Q8303) and dimmer controller (IC8280) circuits.
4-4-2 MICROPHONE CIRCUIT (DISPLAY BOARD)
The AF signals from the microphone are amplified at the AF
amplifier (IC8280) via the "MIC" signal. The signals are
applied to the IC-F7000's main unit through the J2501, pin 1
via the "FMOD" line.
4-4-3 KEY'S BACK LIGHTS CIRCUIT (DISPLAY
BOARD)
The key"s back lights compose of DS8305, DS8306,
DS8308, DS8309, DS8311–DS8314, and are controlled by
the dimmer (Q8301) and dimmer controller (IC8280) circuits.
The dimmer circuit is controlled by the FRONT CPU.
4-4-4 RESET CIRCUIT (DISPLAY BOARD)
The reset IC (IC8202) resets the FRONT CPU (IC8201)
when IC-F7000 is power ON or OFF.
Q5601
Buff
LO
Q5521,
D5521,
L5523
Q5202
Doubler
Q5302
Buff
4 - 6
LCD's
back
light
employs
Q5602
Q5603
Buff
D/A
DDS
convertor
IC5701
5
LEDs
1st LO
(64 94 MHz)
2nd LO
(64 MHz)
3rd LO
(443 kHz)
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