IC-756Pro3_serv.pdf
HF/50MHz ALL MODE TRANSCEIVER SERVICE MANUAL U.S.A. Europe France United Kingdom Italy Korea Spain #32 #33 #34 #35 #38 #39 #40 USA EUR FRA UK ITA KOR ESP INTRODUCTION This service manual describes the latest service information for the IC-756PROIII HF/50MHz ALL MODE TRANSCEIV- ER. DANGER NEVER connect the transceiver to an AC outlet or to a DC power supply that uses more than 16 V. This will ruin the transceiver. DO NOT expose the transceiver to rain, snow or any liquids. DO NOT reverse the polarities of the power supply when con- necting the transceiver. DO NOT apply an RF signal of more than 20 dBm (100 mW) to the antenna connector. This could damage the transceiv- ers front end. ORDERING PARTS Be sure to include the following four points when ordering replacement parts: 1. 10-digit order numbers 2. Component part number and name 3. Equipment model name and unit name 4. Quantity required 1110000960 S.ICNJM4558MIC-756PROIII MAIN-A UNIT 5 pieces 8810005770 Screw BiH M38 ZK IC-756PROIII Top cover10 pieces Addresses are provided on the inside back cover for your convenience. REPAIR NOTES 1. Make sure a problem is internal before disassembling the transceiver. 2. DO NOT open the transceiver until the transceiver is disconnected from its power source. 3. DO NOT force any of the variable components.Turn them slowly and smoothly. 4. DO NOT short any circuits or electronic parts. An insu- lated tuning tool MUST be used for all adjustments. 5. DO NOT keep power ON for a long time when the trans- ceiver is defective. 6. DO NOT transmit power into a signal generator or a sweep generator. 7. ALWAYS connect a 50 dB to 60 dB attenuator between the transceiver and a deviation meter or spectrum ana- lyzer when using such test equipment. 8. READ the instructions of test equipment thoroughly before connecting equipment to the transceiver. To upgrade quality, any electrical or mechanical parts and internal circuits are subject to change without notice or obligation. Icom, Icom Inc. and are registered trademarks of Icom Incorporated (Japan) in the United States, the United Kingdom, Germany, France, Spain, Russia and/or other countries. VER.NO.SYMBOLVERSION TABLE OF CONTENTS SECTION 1SPECIFICATIONS SECTION 2INSIDE VIEWS SECTION 3CIRCUIT DESCRIPTION SECTION 4ADJUSTMENT PROCEDURES SECTION 5PARTS LIST SECTION 6MECHANICAL PARTS AND DISASSEMBLY SECTION 7SEMI-CONDUCTOR INFORMATION SECTION 8BOARD LAYOUTS 8 - 1DISPLAY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 1 8 - 2MODE BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 3 8 - 3PHONE BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 3 8 - 4KEY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 3 8 - 5TEN-KEY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 3 8 - 6PBT BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 5 8 - 7RIT BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 5 8 - 8MIC BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 5 8 - 9MEMORY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 5 8 - 10 MAIN-A UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 7 8 - 11 DSP-A BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 9 8 - 12 RF-B UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 11 8 - 13 BPF-A BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 13 8 - 14 PREAMP BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 13 8 - 15 PLL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 15 8 - 16 PA UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 17 8 - 17 FILTER-A UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 19 8 - 18 CTRL-A UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 - 21 8 - 19 TUNER-A BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8- 23 SECTION 9BLOCK DIAGRAM SECTION 10VOLTAGE DIAGRAMS 10 - 1 FRONT UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 1 10 - 2 DSP-A BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 3 10 - 3 TUNER-A, MEMORY BOARDS AND CTRL-A UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 5 10 - 4 MAIN-A UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 7 10 - 5 PLL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 12 10 - 6 PA AND FILTER-A UNITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 15 10 - 7 BPF-A, PREAMP BOARDS AND RF-B UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 17 SECTION 1 SPECIFICATIONS 1 - 1 GENERAL Frequency coverage: Receive 0.03060.000 MHz*1, *2 Transmit 1.8001.999 MHz*2 3.5003.999 MHz*2 5.3305, 5.3465, 5.3665, 5.3715, 5.4035 MHz*3 7.0007.300 MHz*2 10.10010.150 MHz*2 14.00014.350 MHz*2 18.06818.168 MHz*2 21.00021.450 MHz*2 24.89024.990 MHz*2 28.00029.700 MHz*2 50.00054.000 MHz*2 *1 Some frequency bands are not guaranteed. *2 Depending on version. *3 USA only. Mode : USB, LSB, CW, RTTY, AM, FM Number of memory channels : 101 (99 regular, 2 scan edges) Antenna connector : SO-239 2 (50 ) phono jack (RCA; 50 ) Usable temp. range : 10C to +50C (14F to 122F) Frequency stability : Less than 0.5 ppm from 1 min. after power ON. (10C to +50C; 14F to 122F) Freq. resolution : 1 Hz Power supply requirement: 13.8 V DC 15% (negative ground) Current drain : Transmit max. power 23 A Receive stand-by 3.0 A (typical) max. audio 3.3 A (typical) Dimensions : 340(W)111(H)285(D) mm (proj. not included) ; 338(W)438(H)11732(D) in Weight (approx.) : 9.6 kg (21 lb 3 oz) ACC 1 connector : 8-pin DIN connector ACC 2 connector : 7-pin DIN connector CI-V connector : 2-conductor 3.5(d) mm (18) Display : 5-inch (diagonal) TFT color LCD TRANSMITTER Output power : SSB/CW/RTTY/FM 5100 W AM 540 W Modulation system : SSB PSN modulation AM Low power modulation FM Phase modulation Spurious emission : Less than 50 dB (HF bands) Less than 60 dB (50 MHz band) Carrier suppression : More than 40 dB Unwanted sideband suppression: More than 55 dB TX variable range : 9.999 kHz Mic. connector : 8-pin connector (600 ) ELE-KEY connector: 3-conductor 6.35(d) mm (14) KEY connector : 3-conductor 6.35(d) mm (14) SEND connector : Phono jack (RCA) ALC connector : Phono jack (RCA) RECEIVER Receive system : Triple-conversion superheterodyne system Intermediate frequencies: 1st IF 64.455 MHz 2nd IF 455 kHz 3rd IF 36 kHz Sensitivity : SSB, CW, RTTY (at 2.4 kHz bandwidth) 1.829.99 MHz*1 0.16 V (10 dB S/N) 50.054.0 MHz*2 0.13 V (10 dB S/N) AM (at 6.0 kHz bandwidth) 0.51.799 MHz 13 V (10 dB S/N) 1.829.99 MHz*1 2.0 V (10 dB S/N) 50.054.0 MHz*2 1.0 V (10 dB S/N) FM (at 15 kHz bandwidth) 28.029.99 MHz*1 0.5 V (12 dB SINAD) 50.054.0 MHz*2 0.32 V (12 dB SINAD) *1 Pre-amp 1 ON *2 Pre-amp 2 ON Squelch sensitivity : (Pre-amp OFF) SSB/CW/RTTY Less than 5.6 V FM Less than 1.0 V Selectivity : SSB/RTTY (at 2.4 kHz bandwidth) More than 2.4 kHz/6 dB Less than 3.6 kHz/60 dB CW (at 500 Hz bandwidth) More than 500 Hz/6 dB Less than 700 Hz/60 dB AM (at 6 kHz bandwidth) More than 6.0 kHz/6 dB Less than 15.0 kHz/60 dB FM (at 15 kHz bandwidth) More than 12 kHz/6 dB Less than 20 kHz/60 dB Spurious and image rejection ratio: More than 70 dB (except IF through in 50 MHz band) RIT variable range : 9.999 kHz Audio output power : More than 2.0 W at 10% distortion (at 13.8 V DC) with an 8 load PHONES connector: 3-conductor 6.35(d) mm (14) EXT SP connector : 2-conductor 3.5(d) mm (18) 8 ANTENNA TUNER Matching impedance range: HF bands 16.7 to 150 unbalanced*1 50 MHz band 20 to 125 unbalanced*2 *1 Less than VSWR 3:1 *2 Less than VSWR 2.5:1 Minimum operating input power: 8 W Tuning accuracy : VSWR 1.5:1 or less Insertion loss : Less than 1.0 dB (after tuning) All stated specifications are subject to change without notice or obligation. SECTION 2INSIDE VIEWS 2 - 1 TOP VIEW Fan control circuit PA unit Fan FILTER-A unit TUNER-A unit Antenna tuner CPU (IC5: M38022M2-138FP) Drive amplifier Voltage regulator Common filter (L501: LR-386) Common filter (L502: LR-386) CTRL-A unit Current transformer (L1: LR-364) C-MOS IC (IC14: TC74AC04F) Fan control circuit PA unit Fan FILTER-A unit TUNER-A unit Antenna tuner CPU (IC5: M38022M2-138FP) Drive amplifier Voltage regulator Common filter (L501: LR-386) Common filter (L502: LR-386) CTRL-A unit Current transformer (L1: LR-364) C-MOS IC (IC14: TC74AC04F) Fan control circuit Q10, Q11: 2SC40812 Q12, Q13: 2SB12012 PA unit Cooling fan FILTER-A unit TUNER-A unit Antenna tuner CPU (IC5: M38022M2-138FP) Drive amplifier circuit (Q2, Q3: 2SC19722) Voltage regulator IC1: TA7805F IC2: TA7805S IC3: TA78T08C Common filter (L501: LR-386) Common filter (L502: LR-386) CTRL-A unit Current transformer (L1: LR-364) C-MOS IC (IC14: TC74AC04F) Power amplifier (Q4, Q5: 2SC51252) Power amplifier (Q4, Q5: 2SC51252) Power amplifiers (Q4, Q5: 2SC51252) 2 - 2 BOTTOM VIEW Reference frequency oscillator (X52: CR-338 32.00056MHz) RF-B unit BPF-A board PLL unit 1LO PLL IC (IC381, IC681: LMX2306TM) VCO-B circuit VCO-A circuit S2LO PLL IC (IC901: LC7153M) 1LO DDS IC (IC101, IC401: SC-1246A) 3LO/S3LO DDS IC (IC701, IC801: SC-1287) MAIN-A unit Noise blanker circuit LCD contorller (IC3551: S1D13504F00A000) MAIN CPU (IC3501: HD64F2375F20) TX 3rd mixer (IC221: NJM1496V) RX 3rd mixer (IC151: TC4W53FU) DSP-A board PREAMP board TX 1st mixer (D1451: HSB88WS) FM IF IC (IC2001: TA3116FN) RX 1st mixer circuit RX 2nd mixer (D1752: HSB88WS) TX 2nd mixer (D1852: HSB88WS) Reference frequency oscillator (X52: CR-338 32.00056MHz) RF-B unit BPF-A board PLL unit 1LO PLL IC (IC381, IC681: LMX2306TM) VCO-B circuit VCO-A circuit S2LO PLL IC (IC901: LC7153M) 1LO DDS IC (IC101, IC401: SC-1246A) 3LO/S3LO DDS IC (IC701, IC801: SC-1287) MAIN-A unit Noise blanker circuit LCD contorller (IC3551: S1D13504F00A000) MAIN CPU (IC3501: HD64F2375F20) TX 3rd mixer (IC221: NJM1496V) RX 3rd mixer (IC151: TC4W53FU) DSP-A board PREAMP board TX 1st mixer (D1451: HSB88WS) FM IF IC (IC2001: TA3116FN) RX 1st mixer circuit RX 2nd mixer (D1752: HSB88WS) TX 2nd mixer (D1852: HSB88WS) Reference frequency oscillator (X52: CR-338. 32.00056MHz) RF-B unit BPF-A board PLL unit 1LO PLL IC (IC381, IC681: LMX2306TM) VCO-B circuit VCO-A circuit S2LO PLL IC (IC901: LC7153M) 1LO DDS IC (IC101, IC401: SC-1246A) 3LO/S3LO DDS IC (IC701, IC801: SC-1287) MAIN-A unit Noise blanker circuit LCD contorller (IC3551: S1D13504F00A000) MAIN CPU (IC3501: HD64F2375F20) TX 3rd mixer (IC221: NJM1496V) RX 3rd mixer (IC151: TC4W53FU) DSP-A board PREAMP board TX 1st mixer (D1451: HSB88WS) FM IF IC (IC2001: TA3116FN) RX 1st mixer circuit RX 2nd mixer (D1752: HSB88WS) TX 2nd mixer (D1852: HSB88WS) SECTION 3 CIRCUIT DESCRIPTION 3 - 1 Receiver construction 1st LO B 1st LO A LPF or BPF 2nd LO 64.0 MHz Crystal filter FI1701 1st mixer A Q1203Q1206 1st mixer B Q1003Q1006 2nd mixer D1752 3rd LO 491 kHz 3rd mixer IC151 64.455 MHz 0.0360.0 MHz Ceramic filter FI111 455 kHz to squelch gate (IC301) 36 kHzDSP-A board RF-B UNITMAIN-A UNIT Band Control signal Input diode Band Control signal Input diode 0.031.6 MHzB0D8011115 MHzB7D551 1.62 MHzB1*D32011522 MHzB8D602 23 MHzB2*D33012230 MHzB9D651 34 MHzB3*D34013050 MHzB10WD701 46 MHzB4*D35015054 MHzB10D751 68 MHzB5*D36015460 MHzB10WD701 811 MHzB6D501 3-1 RECEIVER CIRCUIT 3-1-1 RF SWITCHING CIRCUIT (CTRL-A AND RF-B UNITS) The RF switching circuit leads receive signals to bandpass fi lters from an antenna connector while receiving. However, the circuit leads the signal from the RF power amplifier to the antenna connector while transmitting. RF signals from ANT 1 or ANT 2 pass through the an- tenna selector (RL3), transmit/receive switching relays (RL1, RL2, RL4), and low-pass fi lter (L27, L28, C63C66, C105), and are then applied to the RF-B unit via J101 (RF-B unit). The signals from the CTRL-A unit either bypass or pass through the 6 dB (RF-B unit, R102,R106, R111, RL102) and/or 12 dB (RF-B unit, R112, R113, R114, RL103) attenuators via the antenna selector (RL101). By selecting the attenuators, 0 (bypass), 6, 12 and 18 dB attenuations are obtained. The signals are then applied to the RF fi lters. When the RX ANT is selected, the RF signals are passed through the low-pass filter (RF-B unit, L101, L102, C101 C105), then applied to the antenna selector (RF-B unit, RL101). 3-1-2 RF BANDPASS FILTER CIRCUIT (RF-B UNIT AND BPF-A BOARD) RF bandpass fi lters pass only the desired band signals and suppress any undesired band signals. The RF circuit has 11 bandpass fi lters and 1 low-pass fi lter. (1) 0.031.6 MHz (RF-B UNIT) The signals pass through the low-pass filter (L801L802, C802, C805C807), attenuator (R801R803), and are then applied to the RF amplifi ers (Q1001, Q1002). (2) 1.660 MHz (RF-B UNIT AND BPF-A BOARD) The signals pass through the band switch (D104) and high- pass filter (L251L253, C251, C252, C271C274) to sup- press excessively strong signals below 1.6 MHz. The fi ltered signals are applied to one of 11 bandpass fi lters on the table at right abo
