Icom IC-A20MK II Service Manual page 11

3-4 POWER SUPPLY CIRCUITS
3-4-1 INTERNAL/EXTERNAL POWER
SWITCHING CIRCUIT (MAIN UNIT)
When using a battery pack, the relay (RL1001) is OFF and
the [VOL] control (R1035) is connected to the battery pack.
When 13.2 V DC is connected to the [DC IN] jack (J2003),
RL1001 turns ON and R1035 is connected to J2003. In
case of reverse polarity, D1007 is reversely biased,
preventing RL1001 from turning ON and protecting the
transceiver.
3-4-2 VOLTAGE LINES
Description
A voltage line from a battery pack or the [DC 13.8V]
jack.
A common 5 V line from the +5V regulator (01010,
Q1013, Q1014).
A 5 V line from the +5 regulator (D1009, 01015,
01016).
A 5 V line from the T+5 regulator (02010,
Q2015~Q2017). Used for the transmit circuit.
A 5 V line from the R+5 regulator (D1008,
01017-01019). Used for the receive circuit.
CPUS Power source for the CPU. Refer to 3-4-5 below.
3-4-3 AF POWER AMPLIFIER POWER
SOURCE (MAIN UNIT)
The voltage circuit (Q1023, Q1024) provides 9 V for the AF
power amplifier.
PE
3-4-4 POWER SOURCE CIRCUIT FOR OPTION
(RF UNIT)
The current limiter circuit (Q2009, D2009, R2024, R2025,
C2047, C2048) provides approx. 5 V to an option connected
to the [MIC] jack (J2002).
3-4-5 REDUCED VOLTAGE DETECTOR
CIRCUIT (MAIN UNIT)
The CPU (IC3001 on LOGIC UNIT) memorizes operating
frequencies and other settings. While the power is ON, the
+5 line is applied to IC3001 (pins 54, 55, 57) through
D1014.
While the power is OFF, approx. З V is applied to 1C3001
from the lithium battery (BT1001) through D1014 to
preserve memory contents.
CPUS LINE
MAIN :LOGIC
UNIT : UNIT
4 :
BT1001 |
3-5 CPU PORT ALLOCATIONS
Following are CPU explanations and I/O ports.
Description |
Input port for the key matrix.
When the PTT switch is pushed, this
port becomes "HIGH."
When the PLL circuit is unlocked, this
port becomes "HIGH."
When the squelch opens, this port
LOW | becomes "LOW."
LOW When the [LIGHT] switch is pushed,
this port becomes "LOW."
Output port for the PLL serial data
clock.
Output port for the PLL serial data. -
When a VOR signal is received, this
port becomes "HIGH." Input port for the
VOR reference signal.
LIGHTI
aa
aor
When a VOR signal is received, this
port becomes "LOW."
Input port for the VOR variable signal.
When this port is "HIGH," the low
battery indicator appears.
When transmitting, to shift the VCO
oscillation frequency, this port be-
comes "HIGH."
When the navigation band is selected,
this port becomes "HIGH."
When a weather channel is selected,
this port becomes "HIGH."
Outputs beep tones.
Output port for the strobe signal of PLL
serial data.
When transmission is inhibited, this
port becomes "HIGH."
z = о о
> > = >
< Ы 3
When transmitting, this port becomes
"HIGH."
a а
z =
O c
a
When this port is "HIGH," the function
display is illuminated.
Input port for the up signal of the tuning
knob.
Input port for the down signal of the
tuning knob.
Output ports for the initial matrix.
Output ports for the key matrix.
64-
67
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KOKO~
KOK3