Power Supply Circuits; Other Circuits - Icom IC-2SET Service Manual

4-4
POWER
SUPPLY CIRCUITS
4-4-1
VOLTAGE
LINES
LINE
DESCRIPTION
Vcc
The
internal or
attached battery
pack
voltage
or external
DC power passed through the
power
switch.
-1-5
Common
5
V converted from the
Vcc
line at
Q1
and
Q2 on
the
REG UNIT
using IC1
as the
reference voltage.
-I-5S
5
V
controlled by
the
power saver function.
This voltage
is
converted from
Vcc
at
03
and
04
on
the
REG UNIT using IC2 output as the
reference voltage.
R-I-5S
Receive
5
V
controlled
by the
power
saver
function
and
SEND
signal line.
This voltage
is
converted from
Vcc
at
05
and
06
on
the
REG
UNIT using IC3 output as the
reference
voltage.
T-l-5
Transmit 5
V
controlled
by the
TMUTE
signal
line.
This voltage
is
converted from Vcc
at
04
and
05
on the
APC
UNIT.
AF
7
V
AF amp power source controlled
by the
AFS
signal
line.
R14/R15
provides reference
voltage.
4-4-2
CPU
POWER SUPPLY CIRCUIT
(LOGIC UNIT)
When
the
power switch
is
turned
OFF
and
the
internal/externai battery
pack
is
discharged, a voltage
is
appiied
to
the
CPU
(IC1) pin
73
via
R29 from
the
iithium
backup battery (BT1) installed
In
the transceiver to
provide
backup
for
the
memory
contents.
When
the internai
or
attached battery
pack voltage or
external
DC
power
is
applied
to
the transceiver,
BT1
is
charged
using the current regulator (C3).
4-4-3
+5S
AND
R
+
5S
SWITCHING
CIRCUITS (REG
UNIT)
The IC-2SAT/SET has a
power
saver
to
reduce current
consumption
to
approx.
1
/4.
The
PSC
(Power Saver Control) signal
is
applied to IC2.
IC2 controls
+5S
regulator (G3,
C4, D1) to turn
CN
and
CFF +5S
voltage.
PSC
and
SEND
signals
are applied
to ICS.
ICS controls
R-t-5S regulator (05, Q6, D2).
R
+
5S
turns
OFF
during
power saved period or transmitting.
4-4-4
CHARGING
CIRCUIT (PRT UNIT)
Voltage
from
the
[DC 13.8V] jack
is
applied
to
current
control
circuit (01,
02, D5, D6)
to
charge an
internal
or
attached battery
pack
(except the BP-85).
When
the external battery
pack
is
attached, the current
from
D2 charges
the
attached battery pack.
When
the
external battery
pack
is
removed,
the current
from
D2
charges
the internal
battery pack.
The mechanical switch
(MP7) selects the battery packs.
This
circuit
charges
one
of
the battery
packs
in
approx. 15
hours.
Over voltage protector (D4)
decreases the transceiver
circuit
damage
from over voltage
and reverse
polarity
connections
of the
power
supply.
4-5
OTHER
CIRCUITS
4-
5-1
S/RF INDICATOR CIRCUIT
(DET,
MAIN
AND
LOGIC
UNITS)
A
portion of
the
2nd
IF
signal
is
output
from
IC1 pin
12
on
the
DET
UNIT
via the
SD
signal
line.
The
signal
is
rectified at
D1 on
the
MAIN UNIT
to
obtain an S-indicator
signal.
The
S-indicator signal
is
applied
to
IC2b
pin 5
on
the
LOGIC
UNIT.
IC2b
pin
6 receives
an
S-indicator
reference
signal
from
the
CPU KEYSO—3
terminals
via
the
D/A
converter (R11,
R37~R40). The
CPU
terminals increase the reference
signal level.
When
the
D/A
converted
level
becomes
greater than the
5-
indicator
level,
IC2b
pin
7
becomes "LOW." The
CPU
detects the signal
strength
level
using the
KEYS0~3
terminal outputs
and indicates the signal strength level
on the function display
when
receiving the
"LOW"
signal.
While
transmitting,
the
S/RF
indicator
indicates the
selected output power.
S INDICATOR CIRCUIT
4-5-2
DISPLAY
BACKLIGHT
CIRCUIT
(LOGIC
UNIT)
When
the
[LIGHT] switch
is
pushed, pin
77
of
the
CPU
outputs
"HIGH." The
signal
is
applied
to
01
to light
up
the backlight
LEDs
(DS2, DS3).
4
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4