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3-9
EXTERNAL
SPEAKER
The
IC-701
contains
an
internal
speaker,
and
is also
designed so that it can drive an external speaker from the
external (EXT) speaker jack on the rear panel.
Be sure the
impedance of the external speaker is 8 ohms, and remember
that
with
the external
speaker
connected,
the
internal
speaker is disabled.
3-10
HEADPHONES
Any good headphone
set, including stereo type, that have
4-16 ohms impedance can be used.
With the plug inserted
halfway into the PHONES
jack, both the headphone and
speaker will operate.
This is convenient when others wish
to listen in on the station, or you wish to record contacts
using a tape
recorder
connected
to the headphone
jack.
With
a stereo
headphone
set inserted this way, however,
the headphone
will lose the sound on one side.
With the
plug inserted completely, only the headphone works.
3-11
POWER
SUPPLY
It is highly recommended that you use the [C-701PS power
supply
for base
operation.
If you
wish
to use another
power source, make sure that it meets the voltage, current,
and
regulation
requirements.
Pay particular attention to
the
overvoltage
protection
as a runaway
regulator
can
destroy the IC-701.
Make certain that more than 18 Volts
does not get applied to the unit.
When the power switch
is in the
ON
position,
do not
connect
the
power
cord,
antenna,
external
speaker,
Accessory
plug,
or the mi-
crophone to avoid possible trouble.
Be sure not to transmit
with the antenna disconnected.
If the fuse blows, replace
it with
a new 20 Amp fuse after fixing the cause.
Avoid
turning the power switch ON and OFF
repeatedly over a
short time.
Frequent repetitions may cause the frequency
indicator
to display the wrong
frequencies.
If such a
malfunction
should occur, turn OFF the switch and a few
seconds later turn it ON again.
3-12
CAUTIONS
As the unit has already been closely adjusted with highly
sophisticated
measuring
instruments,
never
tamper
with
the turnable resistors, coils, trimmers, etc.
IN
THE
PLL
UNIT,
THE
HEART
OF
THE
TRAN-
SCEIVER, A C-MOS
LSI IS INCORPORATED.
IF THE
SEAL IS BROKEN WHEN A FAILURE OCCURS WITHIN
THE
TERMS
OF
THE
GUARANTEE,
THE
REPAIR
MAY
BE
AT
THE
USERS
EXPENSE,
SO
DO
NOT
ATTEMPT
TO OPEN
THE PLL CASE!
C-MOS
is also used in the digital driver unit as well as the
PLL.
C-MOS
ICs are very susceptible to excessive static
charges
and
over
current
and
care must
be used when
handling
them.
Therefore,
avoid
touching
the
driver
unit and the nearby circuitry unless absolutely necessary.
When
it is necessary
to check
the circuitry, observe the
following points.
Ground
all measuring
instruments, the soldering iron, and
other tools.
Do not connect or disconnect the C-MOS
IC
from
its socket, or solder it when the power is ON.
Do
not apply voltage of less than —0.5 or more than +5 Volts
to the input terminals
of the
IC.
DO
NOT
MEASURE
WITH
AN OHMMETER.
3-13
COOLING
FAN
The rear of the PA unit is designed to achieve effective
natural cooling.
But with 200 Watts input, the final stage
circuit produces quite a bit of heat and its temperature may
rise during a very long, continuous transmission.
If the
temperature becomes high enough, the built-in cooling fan
will start to spin.
The fan is connected to the temperature
monitoring
circuit which detects the temperature of the
final
stage
transistors.
The
operation
of this fan is as
follows:
1. The fan does not work during all reception.
2. During transmission,
it does not work if the detected
temperature is below a certain level.
3. When
the
temperature
exceeds
that
level
during
a
transmission,
the fan will start to move
air across the
heatsink to cool it.
4. If the temperature
of the final stage transistors rises to
the danger point, the fan will turn at a much higher
speed and frequency display will start to flash.
THIS MEANS
STOP TRANSMITTING!
1, 2 and 3 are normal conditions.
4 is abnormal.
If the
meter
and
display
start
to
flash, stop transmitting
and
check for the cause of the excess
heat.
This could be
antenna
mismatch,
environmental
problems,
etc., but be
sure
to rectify the problem
before
beginning to operate
again.
—5—
i
er
A
ae
waa tnt
So
eS aR
OR
lm Li tS AORN eR
ON
the ene en BAM enh Rr
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