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HF/50MHz ALL MODE TRANSCEIVER iC-756pro S-14110XZ-C1-q June. 2007...
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8. READ the instructions of test equipment throughly before connecting a test equipment to the transceiver. Icom, Icom Inc. and logo are registered trademarks of Icom Incorporated (Japan) in the United States, the United Kingdom, Germany, France, Spain, Russia and/or other countries.
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CONTENTS SECTION SPECIFICATIONS SECTION INSIDE VIEWS SECTION CIRCUIT DESCRIPITON SECTION ADJUSTMENT PROCEDURES SECTION PARTS LIST SECTION MECHANICAL PARTS AND DISASSEMBLY SECTION SEMI-CONDUCTOR INFORMATION SECTION BOARD LAYOUTS MODE, PHONE, KEY, PREAMP, BPF-A, DSP-A BOARDS ......8-1 DISPLAY BOARD .
SECTION 3 CIRCUIT DESCRIPTION 3-1 RECEIVER CIRCUIT • Used RF fi lter 3-1-1 RF SWITCHING CIRCUIT Control Input Control Input Band Band (CTRL-A AND RF-B UNITS) signal diode signal diode The RF switching circuit leads receive signals to bandpass 0.03–1.6 MHz D801 11–15 MHz D551...
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3-1-5 1ST IF CIRCUIT (RF-B UNIT) Some DC voltage from the noise detector circuit is fed back to the noise amplifiers (Q271, Q272) via the DC amplifiers The 1st IF circuit filters and amplifies the 1st IF signal. The (Q274, Q275). The DC amplifiers function as an AGC cir- 1st IF signal combined at L1018 and is then applied to a cuit to reduce average noise.
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The converted signal is changed from a 5 V level signal to 3-1-13 S-METER CIRCUIT (MAIN-A UNIT) a 3.3 V signal in the level converter (IC2051), and is then The S-meter circuit indicates the relative received signal applied to the DSP IC (IC2001) for 36 kHz digital IF filter, strength while receiving by utilizing the AGC voltage which demodulation, automatic notch and noise reduction, etc.
3-2 TRANSMITTER CIRCUITS (1) When SSB mode The audio signals from the analog switch (IC2201, pin 5) 3-2-1 MICROPHONE AMPLIFIER CIRCUIT are amplified at the limiter amplifier (IC2281b) and applied (MAIN-A UNIT) to the low-pass filter (IC2281c/d) to limit the transmit The microphone amplifier circuit amplifies microphone passband width.
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3-2-4 SPEECH COMPRESSOR CIRCUIT 3-2-6 RF CIRCUIT (RF-B AND PA UNITS) (DSP-A BOARD) The RF circuit amplifies operating (transmitting) frequency to obtain 100 W of RF output. The speech compressor compresses the transmitter audio input signals to increase the average output level (average The signal from the 1st IF mixer (RF-B unit;...
When the FORV signal exceeds the POCV voltage, ALC The thermistor (R50) detects the temperature of the final bias voltage from the comparator (IC551b) controls the IF amplifier (Q5), and activates Q11 and Q13 to accelerate amplifiers (Q261). This adjusts the output power to a speci- the cooling fan when the detected temperature exceeds fied level from the [RF POWER] control until the FORV and 70˚C (158˚F).
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(1) REFERENCE LOOP PLL 3-3-3 2ND LO AND REFERENCE OSCILLATOR The oscillated signal at the reference VCO (Q151, D151) is CIRCUITS amplified at the buffer amplifiers (Q102, Q152) and is then The reference oscillator (X52, Q51) generates a 32.0 MHz applied to the DDS IC (IC101, pin 46).
3-4 ANTENNA TUNER CIRCUITS (2) Tuning motors (CTRL-A and TUNER-A units) A motor controller (Q211–Q218, D211, D213, D215, D217) 3-4-1 MATCHING CIRCUIT (TUNER-A UNIT) rotates the tuning motors (TUNER-A unit; MF1, MF2) to The matching circuit is a T-network. Using 2 tuning motors, obtain a low SWR.
3-5 SCOPE CIRCUITS 3-6 POWER SUPPLY CIRCUITS 3-5-1 SCOPE RECEIVER CIRCUIT (RF-B UNIT) 3-6-1 PA UNIT A portion of the 64.455 MHz 1st IF signal from the 1st LINE DESCRIPTION mixer circuit (Q1203–Q1206: while receiving) or IF ampli- The voltage from an external power supply via fier (Q1551: while transmitting) is passed through the the common filter circuit (FILTER-A unit;...
3-6-3 MAIN-A UNIT 3-7-2 SUB-CPU PORT ALLOCATIONS (DISPLAY BOARD; IC401) LINE DESCRIPTION Port Receive 8 V converted from the 14 V line and Description number name regulated by the R8V regulator circuit (Q601, Input and output ports for the system OSC1, Q602, D601).
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3-7-3 MAIN-CPU PORT ALLOCATIONS (MAIN-A UNIT; IC3501) Port Port Description Description number name number name A0–A3, CON1 Outputs data signal for the DDS cir- 6–9, Address signal output ports for the A4–A11, (PDAT) cuits (PLL unit; IC101, IC401). 11–18, LCD controller (IC3551). A12–A18 20–26 Outputs clock signal for the DDS cir-...
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3-7-4 INPUT EXPANDER ALLOCATIONS (1) DISPLAY board; IC411 (2) PLL unit; IC101 Port Port Description Description number name number name Input port for the [RIT], [∆TX] and Outputs the marker mute switch [CLEAR] switches. (IC192) control signal. MAKS High : When the marker ON is select- Input port for [UP] and [DN] switches MUDK of the connected microphone.
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(6) RF-B unit; IC402 (4) CTRL-A board; IC11 Port Port Description Description number name number name Outputs a low-pass filter select signal. Outputs a bandpass filter select signal. High : When 0.03–1.999999 MHz High : When 11–13.999999 MHz or B7WS band is selected.
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(8) MAIN-A unit; IC3653 (10) MAIN unit; IC3752 Port Port Description Description number name number name Outputs strobe signals for the out- Outputs control signal for the noise BSTB put expander ICs (RF-B unit; IC301, blanker switch (Q3751, Q3752). IC302). High : When the [NB] switch is ON, except in FM mode.
SECTION 4 ADJUSTMENT PROCEDURE 4-1 PREPARATION ■ REQUIRED TEST EQUIPMENT EQUIPMENT GRADE AND RANGE EQUIPMENT GRADE AND RANGE Output voltage : 13.8 V Frequency range : 300–3000 Hz DC power supply Audio generator Current capacity : 30 A or more Measuring range : 1–500 mV Measuring range...
4-2 PLL ADJUSTMENTS ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST • Display freq. : Any Connect a frequency 64.000000 MHz (R33 REFERENCE for critical • Turn L52 on the PLL unit to 4 rota- counter to the check FREQUENCY tion downside for presetting.
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PLL ADJUSTMENTS—continued ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST S2LO • Display freq. : Any Connect an RF volt- –3 dBm or more Verify OUTPUT • Receiving meter to the check LEVEL point P901. MARKER • Display freq. : Any Connect an oscil- 4 Vp-p or more...
4-3 TRANSMITTER ADJUSTMENTS ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST IDLING • Connect an RF power meter to [ANT1] connector. CURRENT • Turn R14, R16, R65 and R67 on the PA unit to max. CCW. • Disconnect W16 from EP4, and connect an ammeter between W16(+) and EP4(–). (for drive ampli- Measure the cur- •...
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• PA unit PA unit Idling current adjustment point for drive amplifier Top view of the transceiver Ammeter Idling current adjustment point − for drive amplifier Idling current adjustment point for final amplifier Idling current adjustment point for final amplifier •...
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TRANSMITTER ADJUSTMENTS—continued ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST Ic APC • Display freq. : 3.550000 MHz Rear Connect an amme- 23 A MAIN-A R545 • Mode : RTTY panel ter between power • Connect CP501 to GND. s u p p l y a n d t h e •...
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• MAIN-A unit MAIN-A unit Bottom view of the transceiver R509 50 MHz band output power adjustment CP501 Ic APC check point R510 AM carrier R507 adjustment HF bands output power adjustment R545 Ic APC adjustment • DSP-A board DSP-A board MAIN-A unit R2227...
4-4 RECEIVER ADJUSTMENTS ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT JUST RX PEAK • Display freq. : 14.100000 MHz Rear C o n n e c t a n A C Minimum audio output RF-B L1211, • [DUALWATCH] : OFF panel millivoltmeter to [EXT level...
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• RF-B unit RF-B unit L1211 Bottom view of the transceiver L1011 RX peak adjustment C1238 C1036 R1207 L1752 Mixer balance R1206 adjustment L1751 R1007 FM distortion R1006 adjustment L1702 J1651 Mixer ballance check point • MAIN-A unit MAIN-A unit Bottom view of the transceiver L111 L112...
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RECEIVER ADJUSTMENTS—continued ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST RECEIVER • Display freq. : 14.100000 MHz MAIN-A Connect an oscil- 3.7 Vp-p MAIN-A R210 TOTAL GAIN • [DUALWATCH] : OFF loscope to the check • Mode : USB point CP213.
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• MAIN-A unit MAIN-A unit Bottom view of the transceiver L273 Noise L272 blanker L271 adjustment R271 R210 Receiver total gain CP271 adjustment Noise blanker check point CP213 Receiver total gain check point • RF-B unit RF-B unit J2001 Spectrum scope pre-setting Bottom view of the transceiver CP2002...
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4-5 TUNER ADJUSTMENTS ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST • D i s p l ay f r e q . : 29.70000 MHz CTRL-A Connect a digital Minimum voltage CTRL-A DETECTOR • Mode : FM multimeter or oscil- •...
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4-6 METER ADJUSTMENTS ADJUSTMENT ADJUSTMENT CONDITION DISPLAY OPERATION ENTERING 1 • Enter the adjustment mode: ADJUST MODE Push [F-1 (METER)], [F-2 (TX)] or [F-3 (RX)] to q Turn power OFF. ADJUSTMENT select each adjustment mode. w Terminate the [REMOTE] jack MODE Once entering adjustment mode, use [F-1 with a 3.5(d) mm mini-plug.
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METER ADJUSTMENTS–contnued ADJUSTMENT ADJUSTMENT CONDITION DISPLAY OPRATION (50M POWER 7 • Connect an RF power meter to -- TX -- Set the output power to using the tuning dial. METER) [ANT1] connector. POWER 50M Tuner Then push [F-5 (SET)] to store the "POWER •...
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