Main Unit Voltage Line; Vco Unit Voltage Line - Icom IC-2720H Service Manual

4-4-2 MAIN UNIT VOLTAGE LINE

Line
The 13.8V external DC power from the power
HV
connector.
The same voltage as the HV line which is con-
trolled by the VCC regulator circuit (MAIN unit;
Q2001). When the [POWER] switch is pushed,
VCC
the CPU outputs control signal to the power
switch controller (Q2003) to turn the circuit ON.
Common 5 V for the CPU converted from the HV
line by the 5V regulator circuit (IC2002). The volt-
5V
age line is also applied to the CPU when IC-
2720H is power OFF.
Common 8 V converted from the VCC line at the
8V
+8 regulator circuit (IC2003).
Common 5 V produced from the 5 V line by the
+5 regulator circuit (Q2002, D2048). The output
5VS
signal is applied to the PTT detector (Q2005),
mic amplifier (IC2014, Q2028), etc.VHF transmit.
8 V produced from the 8V line at the VT8 regula-
VT8
tor circuit (Q9, Q11).
UHF transmit 8V produced from the 8V line at the
UT8
UT8 regulator circuit (Q10, Q12).
VHF and UHF transmit 8 V produced from the 8
V line at the VUT8 regulator circuit (Q13, D1).
The output voltage is applied to the buffer ampli-
VUT8
fier (Q38), pre-amplifier (Q16) and pre-driver
(Q21).
Receive 5 V produced from the 5VS line at the
L_R5 regulator circuit (Q1000). The output volt-
L_AM5
age is applied to the AM detector for left side dis-
play (Q1014, Q1017).
Receive 5 V produced from the 5VS line at the
R_R5 regulator circuit (Q1002). The output volt-
R_AM5
age is applied to the AM detector for right side
display (Q1022, Q1025).
Receive 5 V produced from the 5VS line at the
L_AM5 regulator circuit (Q1006). The output volt-
L_R5
age is applied to the IF amplifier (Q1040) and FM
IF IC (IC1001) for left side display.
Receive 5 V produced from the 5VS line at the
R_AM5 regulator circuit (Q1005). The output
R_R5
voltage is applied to the IF amplifier (Q1041) and
FM IF IC (IC1004) for right side display.
Receive 5 V produced from the 5VS line at the
L_R5 regulator circuit (Q1). The output voltage is
L140_R5
applied to the RF amplifier (Q29) for left side dis-
play's 144 MHz bandpass filter.
Receive 5 V produced from the 5VS line at the
R_R5 regulator circuit (Q2). The output voltage is
R140_R5
applied to the RF amplifier (Q30) for right side
display's 144 MHz bandpass filter.
Description
MAIN UNIT VOLTAGE LINE–Continued
Line
Receive 5 V produced from the 5VS line at the
R_AM5 regulator circuit (Q3). The output voltage
L220_R5
is applied to the RF amplifier (Q31) for left side
display's 220 MHz bandpass filter.
Receive 5 V produced from the 5VS line at the
L_AM5 regulator circuit (Q4). The output voltage
L300_R5
is applied to the RF amplifier (Q32) for right side
display's 300 MHz bandpass filter.
Receive 5 V produced from the 5VS line at the
R_R5 regulator circuit (Q5). The output voltage is
R400_R5
applied to the RF amplifier (Q19) for right side
display's 430 MHz bandpass filter.
Receive 5 V produced from the 5VS line at the
R_AM5 regulator circuit (Q6). The output voltage
L400_R5
is applied to the RF amplifier (Q20) for left side
display's 430 MHz bandpass filter.
Receive 5 V produced from the 5VS line at the
L_AM5 regulator circuit (Q8). The output voltage
R800_R5
is applied to the RF amplifier (Q18, Q35) for right
side display's 910 MHz bandpass filter.
Common 8 V produced from the 8 V line by the
+8 regulator circuit (Q1023). The output voltage
L_VCO8
is applied to the VCO circuit (RF unit; Q6,
D3–D5) and buffer amplifier (RF unit; Q8).
Common 5 V converted from the HV line by the
+5 regulator circuit (CONTROL unit; IC3). The
output voltage is applied to the buffer amplifier
CPU5
(CONTROL unit; Q2) and reset circuit (CON-
TROL unit; IC2).

4-4-3 VCO UNIT VOLTAGE LINE

Line
Common 8 V converted from the VCC line at the
+8 regulator circuit (MAIN unit; IC2003). The out-
8V
put voltage is applied to the filter switch (IC2),
loop filter (Q2, Q3, D2) and buffer amplifier (Q8).
Common 5 V produced from the 5 V line by the
+5 regulator circuit (MAIN unit; Q2002, D2048).
5VS
The output voltage is applied to the PTT IC (IC1)
and regulator circuit (Q9).
Common 8 V produced from the 8 V line by the
+8 regulator circuit (Q1023). The output voltage
L_VCO8
is applied to the VCO circuit (RF unit; Q6,
D3–D5) and buffer amplifier (RF unit; Q8).
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Description
Description