Other Circuits - Icom ID-800H Service Manual

4-4-3 MAIN UNIT VOLTAGE LINE
Line
The voltage from the external power supply via
HV
the W501.
The same voltage as the HV line which is con-
trolled by the VCC regulator circuit (Q501). The
VCC
circuit is controlled by the power switch control-
ler (Q502).
Common 8 V converted from the VCC line at
8V
the +8 V regulator circuit (IC504).
Transmit 8 V for VHF band controlled by the VT8
VT8 regulator circuit (Q19, Q22) using the "VTXC"
signal from the main CPU (IC505, pin 21).
Transmit 8 V for UHF band controlled by the
UT8 regulator circuit (Q20, Q23) using the
UT8
"UTXC" signal from the main CPU (IC505, pin
20).
Common 5 V converted from the HV line at the
5V
+5 regulator circuit (IC503).
Common 5 V converted from the 5 V line at the
+5S regulator circuit (IC503, D504). The circuit
5VS
is controlled by the power switch controller
(Q502).
VCO 8 V for V-VCO controlled by "V_VCO" sig-
V_VCO8
nal from the CPU (IC505, pin 81).
VCO 8 V for U-VCO controlled by "U_VCO" sig-
U_VCO8
nal from the CPU (IC505, pin 63).
Receive 5 V controlled by the R5 regulator cir-
R5 cuit (Q24) using the "R5CTRL" signal from the
CPU (IC505, pin 78).
Receive 5 V line for AM circuit controlled by the
AM5 AM5 regulator circuit (Q25) using the "AM" sig-
nal from the main CPU (IC505, pin 69).
Receive 5 V line for VHF band circuit controlled
by the VHF_R5 regulator circuit (Q26) using the
VHF_R5
"RXVHF" signal from the main CPU (IC505, pin
73).
Receive 5 V line for UHF band circuit controlled
by the UHF_R5 regulator circuit (Q27) using the
UHF_R5
"RXUHF" signal from the main CPU (IC505, pin
74).
Receive 5 V line for 400 MHz band controlled
by the 400_R5 regulator circuit (Q28) using the
400_R5
"RX400" signal from the main CPU (IC505, pin
67).
Receive 5 V line for 800 MHz band circuit con-
trolled by the 800_R5 regulator circuit (Q29)
800_R5
using the "RX800" signal from the main CPU
(IC505, pin 66).
Description

4-5 OTHER CIRCUITS

4-5-1 SUB CPU RESET CIRCUIT (CONTROL UNIT)
IC2 is the reset voltage detecting circuit. The output voltage
from the +5 regulator circuit (IC5) is applied to the VDD
terminal (IC2, pin 2). IC2 outputs "H" (high) signal to the sub
CPU (IC6, pin 15) when the VDD terminal's voltage is higher
than detecting voltage.
IC6 employs the 8-bit CPU.
4-5-2 LCD AND KEY BACKLIGHT CIRCUIT
(CONTROL UNIT)
The sub CPU (IC6) outputs +8 regulator circuit (Q1, Q3,
D5) control signal from pin 2. The voltage from +8 regulator
circuit is applied to the key backlights (DS13–DS18, DS20,
DS23) and LCD backlights (DS21, DS22).
The backlight color is controlled by the sub CPU via the color
control circuit (Q6, Q7). The backlight has 3 colors (Amber,
Green and Yellow).
4-5-3 WATHER ALART (USA version only)
A portion of the demodulated audio signals from the AM/FM
switch (IC5, pin 1) are passed through the low-pass filter
(R46, R52, C52, C53), and then applied to the main CPU
(IC505, pin 42) via the "WXALT" signal to detect WX alert
signal.
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