Icom IC-A110, Service Manual Addendum

Page: 47 / 79

3 - 5
3-4 POWER SUPPLY CIRCUITS
VOLTAGE LINES (MAIN UNIT)
LINE
VCC
8V
+5V
CPU5V
T8
R8
DESCRIPTION
The voltage from the external DC power con-
nector which is controlled by the power switch
([VOL] control).
Common 8 V converted from the VCC line by the
+8 V regulator circuit (IC29). The output voltage
is applied to the +5 V regulator circuit (IC7), the
ripple filter (Q16), and etc.
Common 5 V converted from the 8V line by the
+5V regulator (IC7) and +5V current amplifier
(Q22, Q23, D15) circuits. The output voltage is
applied to the electric volume IC (IC13), buffer
amplifiers (Q68, Q69), and etc.
Common 5 V converted from the VCC line by +8
V regulator (Q82, D35) and +5 V regulator cir-
cuits (IC26). The output 5 V voltage is applied to
the CPU (FRONT unit; IC1).
8 V for transmitter circuits regulated by the +8 V
regulator circuit (IC29).
8 V for receiver circuits regulated by the +8 V
regulator circuit (IC29).
3-5 PORT ALLOCATIONS
3-5-1 OUTPUT EXPANDER IC (FRONT UNIT: IC5)
Pin
number
4, 5
6
7
11
12
13
14
Port
name
LED1,
LED2
TRC
R/T
SMUT
AFMUT
RMUT
TMUT
Description
Outputs backlight control signals.
Outputs control signal to the MOD/AF
swtich (MAIN unit: IC48, pin 5) and
etc.
High: While transmitting.
Outputs control signal to the TX/RX
switch (MAIN unit: Q58, pin 1) for
VCO.
Low: While transmitting.
Outputs AF mute swtich (MAIN unit:
IC30, Q86, Q75, Q74, D43) control
signal.
Low: While squelched.
Outputs control signal to the mute
switch (MAIN unit; Q100, Q101, D66)
for speaker amplifier, and etc.
Low: While the speaker output is
muted.
Outputs RMUTE switch (IC6) control
signal.
Low: While squelched.
Outputs T8 regulator control signal.
Low: When TX is muted.
LED1
Low
High
Low
High
LED2
Low
Low
High
High
Backlight condition
Light OFF
No establishment
Light ON, Dimmer ON
Light ON, Dimmer OFF