Icom IC-7000 Service Manual - Page 13

Logic Circuits, Power Supply Circuits, 5-1 Front Unit Voltage Line, 2nd Lo And Reference Oscillator

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3-3-3 2ND LO AND REFERENCE OSCILLATOR CIRCUITS (DDS UNIT) The reference oscillator (X1, Q1) generates a 24.8064 MHz frequency used for the 1st LO, 3rd LO and DSP circuits as a system clock and for the 2nd LO signal. The oscillated signal is multiplied by 5 at Q101 and then passed through the bandpass filter (FI101). The filtered 124.032 MHz signal is amplified at Q151 and then applied to the 2nd mixer circuit (MAIN unit) after being passed through the low-pass filter (L153, C154-C156) and attenuator (R157 -R159) via J151 as the 2nd LO signal. 3-3-4 3RD LO CIRCUIT (DDS UNIT) The 3rd LO circuit generates a 3rd LO signal and shift the frequency for the operating mode needed. The DDS IC (IC51) generates a 10-bit digital signal. The 24.8064 MHz system clock signal from the reference oscillator (X1, Q1) is buffer amplified at IC61 (pins 2, 4) and then applied to DDS IC (IC51, pins 5, 10). The DDS IC (IC51) generates the 438.85 kHz frequency signal and then output from pin 10. The output signal is applied to the low-pass filter (L53, C59-C61) and then applied to the 3rd mixer circuit (MAIN unit) via J952 (pin 13) as the 3rd LO signal. • 3RD LO FREQUENCY Mode RX frequency [kHz] TX frequency [kHz] USB 440.350 440.350 LSB 437.350 437.350 CW 438.850 (-CW PITCH) 438.850 CW-R 438.850 (+CW PITCH) 438.850 RTTY 436.555* 436.555* RTTY-R 440.975* 436.555* AM 438.850 438.850 FM 438.850 438.850 *RTTY TONE: 2125 Hz, RTTY SHIFT: 170 Hz 3-4 LOGIC CIRCUITS 3-4-1 BAND SELECTION DATA Frequency [MHz] IC2151 (MAIN) IC2152 (MAIN) IC2152 (MAIN) IC981 (PA) HPF (MAIN) LPF (PA) 0.03-1.599999 B0 1.6-1.999999 B1 L1 2.0-3.399999 B2 3.4-3.999999 4.0-6.899999 B3 L2 6.9-7.300000 L3 7.300001-7.999999 8.0-10.999999 B4 L4 11.0-13.899999 13.9-14.350000 14.350001- 14.999999 B5 15.0-20.899999 L5 20.9-21.45 21.450001- 21.999999 B6 L6 22.0-29.999999 30.0-49.999999 T: B1 R: B7 50.0-54.0 B7 L7 54.000001- T: B1 59.999999 R: B7 60.0-115.512999 115.513- 128.999999 129.0-148.0 L8 L8 148.000001- 199.999999 400.0-470.0 L9 L9 IC901 (DDS) LOF (DDS) LOF1 LOF2 LOF3 LOF4 LOF5 LOF6 3-5 POWER SUPPLY CIRCUITS 3-5-1 FRONT UNIT VOLTAGE LINE Line Description 3.3 V Common 3.3 V converted from the 5 V line by the 3.3 V regulator circuit (IC151). The output voltage is applied to the sub CPU (IC2003), etc. Common 5 V converted from the 8 V line by 5 V the 5 V regulator circuit (IC101). The output voltage is applied to the LCD driver (IC506), etc. 3 - 8

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3-5 POWER SUPPLY CIRCUITS
3-5-1 FRONT UNIT VOLTAGE LINE
Line
Description
3.3 V
Common 3.3 V converted from the 5 V line
by the 3.3 V regulator circuit (IC151). The out-
put voltage is applied to the sub CPU (IC2003),
etc.
5 V
Common 5 V converted from the 8 V line by
the 5 V regulator circuit (IC101). The output
voltage is applied to the LCD driver (IC506),
etc.
3-3-3
2ND LO AND REFERENCE OSCILLATOR
CIRCUITS (DDS UNIT)
The reference oscillator (X1, Q1) generates a 24.8064 MHz
frequency used for the 1st LO, 3rd LO and DSP circuits as a
system clock and for the 2nd LO signal.
The oscillated signal is multiplied by 5 at Q101 and then
passed through the bandpass filter (FI101). The filtered
124.032 MHz signal is amplified at Q151 and then applied to
the 2nd mixer circuit (MAIN unit) after being passed through
the low-pass filter (L153, C154–C156) and attenuator (R157
–R159) via J151 as the 2nd LO signal.
3-3-4 3RD LO CIRCUIT (DDS UNIT)
The 3rd LO circuit generates a 3rd LO signal and shift the
frequency for the operating mode needed.
The DDS IC (IC51) generates a 10-bit digital signal. The
24.8064 MHz system clock signal from the reference oscil-
lator (X1, Q1) is buffer amplified at IC61 (pins 2, 4) and then
applied to DDS IC (IC51, pins 5, 10). The DDS IC (IC51)
generates the 438.85 kHz frequency signal and then output
from pin 10. The output signal is applied to the low-pass fil-
ter (L53, C59–C61) and then applied to the 3rd mixer circuit
(MAIN unit) via J952 (pin 13) as the 3rd LO signal.
• 3RD LO FREQUENCY
Mode
RX frequency
[kHz]
TX frequency
[kHz]
USB
440.350
440.350
LSB
437.350
437.350
CW
438.850
(–CW PITCH)
438.850
CW-R
438.850
(+CW PITCH)
438.850
RTTY
436.555*
436.555*
RTTY-R
440.975*
436.555*
AM
438.850
438.850
FM
438.850
438.850
*RTTY TONE: 2125 Hz, RTTY SHIFT: 170 Hz
3-4 LOGIC CIRCUITS
3-4-1
BAND SELECTION DATA
Frequency
[MHz]
IC2151
(MAIN)
IC2152
(MAIN)
IC2152
(MAIN)
IC981
(PA)
IC901
(DDS)
HPF
(MAIN)
LPF (PA)
LOF
(DDS)
0.03–1.599999
B0
L1
LOF1
1.6–1.999999
B1
2.0–3.399999
B2
L2
3.4–3.999999
B3
4.0–6.899999
L3
6.9–7.300000
B4
7.300001–7.999999
L4
8.0–10.999999
11.0–13.899999
13.9–14.350000
B5
14.350001–
14.999999
L5
15.0–20.899999
20.9–21.45
B6
21.450001–
21.999999
L6
22.0–29.999999
30.0–49.999999
T: B1
R: B7
L7
LOF2
50.0–54.0
B7
54.000001–
59.999999
T: B1
R: B7
60.0–115.512999
L8
L8
LOF3
115.513–
128.999999
LOF4
129.0-148.0
148.000001–
199.999999
LOF5
400.0–470.0
L9
L9
LOF6
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