Icom IC-701

enough to prevent damage. To indicate the dangerously
high temperature, all the luminous indicators on the front
panel begin blinking. This is done by the autodimmer
circuit composed of 014, and O15. The output of the free
running multivibrator, Q11 and Q12, and driven by the
voltage through Q10 is applied to the circuit.
6-6-2 AUTODIMMER CIRCUIT
R20 in the driver unit is a cadmuim sulfide (CdS) element
to detect brightness of the surrounding light. It’s output
is applied to the Schmitt trigger circuit composed of Q14
and Q15 through the dimmer change over switch in the “’*B”’
unit. The output of this circuit is connected to 016 which
conducts when the surroundings are bright and a voltage
of about 12.5 Volts is obtained from the emitter of O16.
This voltage turns ON lamps through D9. The output from
the emitter of Q16 through R66 is fed to the Zener diode
(D37) in the “A” unit to obtain 5 Volts which is driven by
Q1 to light each LED. When the surroundings are dark,
Q16 turns OFF and the voitage for lamps on the front panel
is fed from the 13.8 Volt line through R20 (47 ohms)
which drops the supply voltage for lamps to about 8.5
Volts. With Q16 in the ““B”’ unit is OFF, a voltage of about
7 Volts is obtained from the Zener diode D8 and fed to
R66 through D28. This voltage is reduced by half with
R66 and R247 in the “A” unit and driven by Q1 to light
each LED with about 2 Volts.
6-6-3 VOX AND CW BREAK-IN CIRCUIT
The voice signals from the microphone are amplified by
Q18 through Q20 and detected by Q21 to drive Q22. Q22
switches the power supply line ON and OFF corresponding
to voice signals. C78, R120 (VOX DELAY control) and
R121 compose a circuit to determine the time constant to
the VOX circuit. The output of this circuit is amplified by
Q7 and Q8 to drive O9 to switch the transmit circuit ON
and OFF. The anti-VOX circuit prevents erroneous ope-
ration of the VOX circuit caused by sound from the speaker.
Signals from the speaker are amplified by Q24, Q25, and
Q26 through R131 (ANTI VOX GAIN Control). These are
then fed to Q23 to raise emitter voltage of Q21 which
reduces the sensitivity of the detector circuit.
The CW break-in circuit is composed of Q5 and Q6 amplify-
ing the signals from the key at O5 and feeding it to O6 for
switching the power supply voltage ON and OFF. This
ON-OFF voltage is fed to the circuit composed of C14, R32
(CW DELAY Control) and R33 having the specified time
constant to control the transmit circuit by way of Q7,
Q8, and Q9.
6-6-4 CW MONITORING CIRCUIT
Q7 in the “B” unit is a CR phase shifting oscillator whose
frequency is set to about 900Hz. Q8 is a switching circuit
to make and break a ground path for C45 so as to vary the
gain of Q7 for switching the oscillation ON and OFF. The
oscillating output passing through R32 (CW MONI volume
control) is fed to the 8th Pin of the AF amplifier circuit
IC1 to drive the speaker.
AC POWER SUPPLY
This set is designed to operate on 13.8 Volts DC. However,
a special AC power supply, the !C-701PS is available for
AC operation. The IC-701PS provides 13.8 Volts at 20
Amps. When connected to the IC-701 transceiver, the
power supply ON-OFF operation is remotely controlled by
the power ON-OFF switch on the IC-701.
Mi SPECIFICATIONS
e Number of Semi- Silicon diode 3
conductors: LED 1
® Input Voltage 117/230V AC (50/60Hz)
(suitable voltage):
e Allowable voltage
fluctuation:
© Input Capacity:
e Output Voltage:
e Max. Load Current:
+10% of input voltage (suitable
line voltage)
360VA (at 20A load)
DC13.8V (at 20A load)
20A (10 minutes ON/10 minutes
OFF 50% duty cycle)
Negative ground
125 x 77 mm
2 watt nominal input
4 watt maximum
110(H) x 180(W) x 260(D) mm
Approximately 8 kg
AC power cord 1
Spare fuse 2
Speaker cord 1
® Polarization:
e Internal Speaker:
e Dimensions:
e Weight:
e Accessories included:
ae encasement tthe iP aii akan AA chee ener Renin Met