Power Supply Circuits - Icom IC-F2610 Service Manual

The lock voltage is also used for the receiver tunable band-
pass filters to match the filter's center frequency to the
desired receive frequency. The lock voltage is amplified at
the buffer amplifier (Q29) and is then applied to the band-
pass filters (D7–D11, D514).
4-3-2 VCO CIRCUIT
The VCO circuit contains a separate Rx VCO (Q21, D19,
D20) and Tx VCO (Q23, D21, D22, D46). The oscillated sig-
nal is amplified at the buffer amplifiers (Q19, Q20) and is
then applied to the T/R switches (D17, D18). Then the
receive 1st LO (Rx) signal is applied to the 1st mixer (Q2) via
the LO amplifier (Q3) and the transmit (Tx) signal to the dri-
ver (Q17).
A portion of the signal from the buffer amplifier (Q19) is fed
back to the PLL IC (IC12, pin 11) via the another buffer
amplifier (Q18) as the comparison signal.
• PLL circuit
12.6 MHz
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Loop
filter
D21, D22, D46
Charge
pump
IC12 (PLL IC)
6
X501
20
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4-4 POWER SUPPLY CIRCUIT
VOLTAGE LINE
LINE
HV
VCC
CPU5V
+5V
+8V
R8V
T8V
MT8V
Rx VCO
Q21,
D19, D20
Buffer
Q19
Tx VCO
Q23,
Phase Programmable
detector counter
Programmable
Shift register
divider
4 - 4
DESCRIPTION
The voltage from the external power connector.
Same voltage as the HV line passed through the
power control circuit (Q12, Q14) controlled by
PWON signal from the CPU (IC20, pin 77).
Common 5 V converted from the HV line at the
5V regulator circuit (IC17). This voltage is sup-
plied to the CPU regardless of the power switch.
Common 5 V converted from the VCC line at the
+5V regulator circuit (Q42, Q43, D30) using the
CPU5V line voltage as the reference.
Common 8 V converted from the VCC line at the
+8V regulator circuit (IC16).
Receive 8 V converted from the VCC line at the
R8V regulator circuit (Q36, D27) using the +8V
line voltage as the reference and controlled by
VRX signal from the CPU (IC20, pin 76).
Transmit 8 V converted from the VCC line at the
T8V regulator circuit (Q40, D29) using the +8V
line voltage as the reference and controlled by
VTX signal from the the CPU (IC20, pin 75).
Transmit 8 V converted from the VCC line at the
MT8V regulator circuit (Q38, D28) using the +8V
line voltage as the reference and controlled by
TMUT signal from the the CPU (IC20, pin 62).
Buffer
D18
to 1st mixer circuit
Q20
D17
to transmitter circuit
Buffer
Q18
11
Prescaler
17
PSTB
18
PCK
19
PDA