Power Supply Circuits - Icom IC-R7000 Service Manual

4·1·27 SQUELCH SWITCH CIRCUIT (MAIN UNIT)
The base of Q2 receives output voltage from IC7(B)
via 027 when the noise squelch is activated, or
output voltage from IC4(B) via 020 when the meter
squelch is activated. Q2 switches 03.
Q6
turns Q1
(the squelch switch) ON and OFF, and Q1 switches AF
signals. The collector voltage of 03 is applied to
the base of Q4. The, and the output of Q4 lights up
the "SIG" INDICATOR on the FREQUENCY DISPLAY.
4·1·28 VSC (Voice Scanning Control) CIRCUIT
(MAIN UNIT)
This circuit sends the VSC signal to the LOGIC UNIT
when the IC·R7000 receives signals with AF signal
components.
Output from Q1 is fed to IC1{A). An active low-pass
filter consisting of IC1(A), R7-R12, and C6-C10
blocks signals higher than 1 kHz to prevent circuit
malfunctions. Output from IC1(A) is amplified by
IC1 (B). 02 detects AF signal components in the
output of IC1(B), and then the detected voltage is
charged at C15. The voltage of C15 is applied to
comparator IC2(A). IC2(A) outputs "HIGH" output
to pin 7 only when receiving signals with AF signal
components.
Q5 and Q7 control relay RL 1 for the [RECORDER-
REMOTE] JACK. RL 1 turns ON when the squelch
opens. VSC operation is given priority even when the
squelch opens. When the VSC function is activated,
the MO signal form the LOGIC UNIT is applied to 07,
and RL 1 turns OFF.
4·1·29 SCANNING CONTROL CIRCUIT (MAIN UNIT)
Output from the center detector circuit and the MUTE
signal from the LOGIC UNIT is applied to the base of
Q10. 010 turns OFF only when the CENT signal and
MUTE signal is "LOW" (the squelch opens when the
receiver is tuned to the center frequen~y). When Q10
turns OFF, a STOP signal is sent to the LOGIC UNIT
via R72 and Q11, and scanning stops.
Q11 switches the STOP signal OFF when the
[SQUELCH] CONTROL is turned fully counterclock-
wise.
4·1·30 METER CIRCUIT (MAIN UNIT)
(a) S·METER CIRCUIT
In FM (wide} mode, the METER receives $-meter (SM)
signals via D16 when receiving a strong signal, or SM
signals from IC4(A) via 015 when receiving a weak
signal.
In FM (narrow), SSB or AM modes, the METER receives
SM signals via D18.
4-6
(b) CENTER METER CIRCUIT
CENT signal from the IF UNIT is inversion-amplified
at IC2(B). Output voltage from IC2(B) is applied to
the METER as a center meter (CM) signal.
In SSB mode, Q17 turns the center (CENT) signal
from IC5 and the center meter (CM) signal from
IC2(B) OFF.
4·1·31 AUDIO FREQUENCY (AF) AMPLIFIER CIRCUIT
(MAIN UNIT)
Output from Q1 is applied to IC3(B) (pin 1). The
[AF GAIN] CONTROL controls the voltage of IC3(B)
(pin 13) to vary the AF gain.
Output from IC3(B) is amplified up to a sufficent AF
level by IC8 to drive the speaker SP1.
Output from Q1 is also applied to buffer amplifier
IC3(A). Output from IC3(A) is fed to the [RECORDER·
REMOTE] JACK.
Q18 amplifies SPK signals from the optional IC-EX310
VOICE SYNTHESIZER UNIT, and signals from Q18
are applied to IC3(B).
4·2 POWER SUPPLY CIRCUITS
4·2·1 REG CIRCUIT (REG UNIT)
The AC power source from the AC POWER SOCKET
is fed to T1.
Voltage from T1 is rectified by 01, next it is then fed
to the stabilization circuit consising of Q1, Q2, and
Q3, and then it is supplied to other circuits.
4·2·2 DC·DC CONVERTER CIRCUIT
(DC·DC UNIT)
This circuit converts 13.8V DC from the REG UNIT
to -7V, -12V and +24V DC voltage. This circuit
consists of a oscillation circuit, a voltage step up/
down transformer, and three regulator circuits.
(MAIN UNIT)
RL2 is a power ON/OFF switch operated by the
optional RC-12 WIRELESS REMOTE CONTROLLER.
The power control (POC) signal from the RC-12
switches Q13 and 013 switches RL 12.
IC6 is a voltage regulator that supplies a stabilized
9V to the MAIN UNIT, IF UNIT and RF UNIT.