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1、HF/50MHz ALL MODE TRANSCEIVER i756PRO SERVICE MANUAL VERSION U.S.A. Europe France SYMBOL USA EUR FRA INTRODUCTION This service manual describes the latest service information for the IC-756PRO HF/50MHz ALL MODE TRANSCEIVER. DANGER NEVER connect the transceiver to an AC outlet or to a DC power supply
2、 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 conecting the transceiver. DO NOT apply an RF signal of more than 20 dBm (100 mW) to the antenna connector.This could damage t
3、he transceIers 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 1110000960S.ICNJM4558MIC-756PRO MAIN UNIT5 pieces 8810005770 S
4、crewBiH M38 ZKIC-756PRO 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
5、 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 gen
6、erator 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. MODEL IC-756PRO To upg
7、rade quality, any electrical or mechanical parts and internal circuits are subject to change without notice or obligation. TABLE OF CONTENTS SECTION 1SPECIFICATIONS SECTION 2INSIDE VIEWS SECTION 3CIRCUIT DESCRIPTION 3 - 1RECEIVER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 1 3 - 2TRANSMITTER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 - 4 3 - 3PLL CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9、. . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 6 3 - 4ANTENNA TUNER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 7 3 - 5SCOPE CIRCUIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10、 . . . . . . . . . . . . . . . . . . . . . . 3 - 8 3 - 6POWER SUPPLY CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 9 3 - 7LOGIC CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11、. . . . . . . . . . . . . . . . . . 3 - 10 SECTION 4ADJUSTMENT PROCEDURES 4 - 1PREPARATION BEFORE SERVICING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 1 4 - 2PLL ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12、 . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2 4 - 3RECEIVER ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 4 4 - 4TRANSMITTER ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13、. . . . . . . . . . . . . . 4 - 8 4 - 5TUNER ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 10 SECTION 5PARTS LIST SECTION 6MECHANICAL PARTS SECTION 7SEMI-CONDUCTOR INFORMATION SECTION 8BOARD LAYOUTS 8 - 1PBT, RIT AN
14、D MIC BOARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 1 8 - 2DISPLAY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 2 8 - 3MODE, PHONE, KEY
15、AND TEN-KEY BOARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 4 8 - 4RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 6 8 - 5PLL UNIT . . . . . . . . . . .
16、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 8 8 - 6MAIN UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 10 8 - 7DSP BOARD . . . .
17、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 12 8 - 8MEMORY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 13 8 - 9PA UNIT . . . . .
18、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 14 8 - 10 FILTER UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 15 8 - 11 TU
19、NER BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 16 8 - 12 CTRL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 17
20、 SECTION 9BLOCK DIAGRAM SECTION 10VOLTAGE DIAGRAM 10 - 1 FRONT UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 1 10 - 2 DSP BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21、. . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 2 10 - 3 TUNER, MEMORY BOARDS AND CTRL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 3 10 - 4 MAIN UNIT (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22、 . . . . . . . . . . . . . . . . . . 10 - 4 10 - 5 MAIN UNIT (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 5 10 - 6 PLL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23、. . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 6 10 - 7 PAAND FILTER UNITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 7 10 - 8 RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 8 SECTION 1SPECIFICATIONS 1 - 1 I GENERAL Frequency coverage: Receive0.03060.000 MHz*1, *2 Transmit1.8001.999 MHz*23.5003.999 MHz*2 7.0007.300 MHz*210.10010.150 MHz*2 14.00014.350 MHz*218.06818.168 MHz*2 21.00021.450 MHz*224.89024.990 M
25、Hz*2 28.00029.700 MHz*250.00054.000 MHz*2 *1Some frequency bands are not guaranteed. *2Depending on version. Mode: USB, LSB, CW, RTTY, AM, FM Number of memory channels : 101 (99 regular, 2 scan edges) Antenna connector : SO-239 2 and phono (RCA); 50 Usable temp. range: 10C to +50C (14F to 122F) Freq
26、uency stability : Less than 0.5 ppm from 1 min. after power ON. Freq. resolution: 1 Hz Power supply: 13.8 V DC 15 % (negative ground) requirement Current consumption: Transmitmax. power23 A Receivestand-by3.0 A (typical) max. audio3.3 A (typical) Dimensions: 340 (W) 111(H) 285(D) mm 1338(W) 438(H) 1
27、1732(D) in Weight: 9.6 kg (21 lb 1 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 I TRANSMITTER Output power: SSB/CW/RTTY/FM5100 W AM540 W Modulation system : SSBPSN modulation AMLow po
28、wer modulation FMPhase 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(
29、d) mm (14) KEY connector: 3-conductor 6.35(d) mm (14) SEND connector: Phono (RCA) ALC connector: Phono (RCA) I RECEIVER Receive system: Triple-conversion superheterodyne Intermediate frequencies: 1st IF frequency64.455 MHz 2nd IF frequency455 kHz 3rd IF frequency36 kHz Sensitivity: SSB, CW, RTTY (at
30、 2.4 kHz bandwidth) 1.829.99 MHz*10.16 V (10 dB S/N) 50.054.0 MHz*20.13 V (10 dB S/N) AM (at 6.0 kHz bandwidth) 0.51.799 MHz13 V (10 dB S/N) 1.829.99 MHz*12.0 V (10 dB S/N) 50.054.0 MHz*21.0 V (10 dB S/N) FM (at 15 kHz bandwidth) 28.029.99 MHz*10.5 V (12 dB SINAD) 50.054.0 MHz*20.32 V (12 dB SINAD)
31、*1Pre-amp 1 ON *2Pre-amp 2 ON Squelch sensitivity : (Pre-amp OFF) SSB/CW/RTTYLess than 5.6 V FMLess than 1.0 V Selectivity: SSB/RTTY (at 2.4 kHz bandwidth) More than 2.4 kHz/6 dB Less than 2.8 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) Mor
32、e 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: More than 70 dB rejection ratio(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
33、)with an 8 load PHONES connector: 3-conductor 6.35 (d) mm (14) EXT SP connector : 2-conductor 3.5 (d) mm (18) 8 I ANTENNA TUNER Matching impedance range: HF bands16.7 to 150 unbalanced*1 50 MHz band20 to 125 unbalanced*2 *1Less than VSWR 3:1; *2Less than VSWR 2.5:1 Minimum operating input power: HF
34、bands: 8 W 50 MHz band: 15 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 BOTTOM VIEW VCO-B circuit YGR amplifier (IC151: PC1678G) Pre amplifier (IC451: PC
35、1658G) FM IF IC (IC841: TA31136FN) RF unit 1st IF filter (FI132: SFPC455E-TC01) 2nd IF filter (FI111: CFK455E10) 3rd mixer (IC151: NJM1496V) MAIN unit PLL unit MEMORY board DSP board VCO-A circuit Ceramic filter (FI842: CFJ455K8) 2 - 2 TOP VIEW FILTER unit Current transformer (L1: LR-364) C-MOS IC (
36、IC14: TC74AC04F) FAN TUNER unit Fan control circuit Antenna tuner CPU (IC5: M38022M2-138FP) CTRL unit Common filter (L501, L502: LR-386) PA unit Drive amplifier SECTION 3CIRCUIT DESCRIPTION 3 - 1 3-1 RECEIVER CIRCUITS 3-1-1 RF SWITCHING CIRCUIT (CTRL AND RF UNITS) The RF switching circuit leads rece
37、ive signals to bandpass filters 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 anten- na selector (RL3), transmit/receive switching relays (RL1,
38、RL2, RL4), and low-pass filter (L27, L28, C63C66, C105), and are then applied to the RF unit via J2. The signals from the CTRL unit either bypass or pass through the 6 dB (RF unit, RL121, R121) and/or 12 dB (RF unit, RL122, R123) attenuators via the antenna selector (RL101). By selecting the attenua
39、tors, 0 (bypass), 6, 12 and 18 dB attenuations are obtained. The signals are then applied to the RF filters. When the RX ANT is selected, the RF signals are passed through the low-pass filter (RF unit, L112, L111, C111C116), then applied to the antenna selector (RF unit, RL101). 3-1-2 RF BANDPASS FI
40、LTER CIRCUIT (RF UNIT) RF bandpass filters pass only the desired band signals and suppress any undesired band signals. The RF circuit has 11 bandpass filters and 1 low-pass filter. (1) 0.031.6 MHz The signals pass through the low-pass filter (L181L183, C181C185), attenuator (R181R183), and are then
41、applied to the RF amplifiers (Q501, Q601). (2) 1.660 MHz The signals pass through the high-pass filter (L171L174, C171C174) to suppress excessively strong signals below 1.6 MHz. The filtered signals are applied to one of 11 band- pass filters as below, and then applied to or bypassed the pre-amplifi
42、er circuit. 3-1-3 PRE-AMPLIFIER CIRCUITS (RF UNIT) The IC-756PRO has 2 gain levels of pre-amplifier circuits. One has 10 dB gain over a wide band frequency range and the other one has 16 dB gain for the 2128 MHz bands. When the PREAMP switch is set to PRE1 or PRE2, the signals are applied to the pre
43、-amplifier 1 (Q441, Q442) or pre-amplifier 2 (IC451) circuit, respectively. Pre-amplified or bypassed signals are applied to the RF amplifier circuits (Q501, Q601). 3-1-4 RF AMPLIFIER AND 1ST MIXER CIRCUITS (RF UNIT) The 1st mixer circuit mixes the receive signals with the 1st LO signal to convert t
44、he receive signal frequencies into a 64.455 MHz 1st IF signal. The IC-756PRO has two 1st mixer circuits for the dualwatch function. The signals from the pre-amplifier circuit, or signals which bypass the pre-amplifiers, are divided at L491. Each signal is applied to a 60 MHz cut-off low-pass filter,
45、 RF amplifier (Q501, Q601) and then to a 1st mixer (Q511Q514 or Q611Q614). Each 1st LO signal (64.4850124.4550 MHz) enters the RF unit from the PLL unit via J561 or J661. The LO signals are amplified at the LO amplifier (Q561 or Q661), filtered by a low-pass filter, and then applied to each 1st mixe
46、r. Used RF filter Receiver construction LPF or BPF 1st LO B 1st LO A 2nd LO 64.0 MHz Crystal filter FI711 1st mixer A Q511Q614 1st mixer B Q611Q614 2nd mixer Q941Q944 3rd LO 491 kHz 3rd mixer IC151 64.455 MHz 0.0360.0 MHz Ceramic filter FI132, FI111 455 kHz to squelch gate (IC301) 36 kHzDSP board RF
47、 UNITMAIN UNIT Band 0.031.6 MHz 1.62 MHz 23 MHz 34 MHz 46 MHz 68 MHz 811 MHz Band 1115 MHz 1522 MHz 2230 MHz 3050 MHz 5054 MHz 5460 MHz Control signal B7 B8 B9 B10W B10 B10W Control signal B0 B1 B2 B3 B4 B5 B6 Input diode N/A D191 D211 D23112 D23112 D271 D29112 Input diode D311 D231 D29112 D391 D371
48、 D391 3 - 2 3-1-5 1ST IF CIRCUIT (RF UNIT) The 1st IF circuit filters and amplifies the 1st IF signal. The 1st IF signal combined at L653 is applied to an MCF (Monolithic Crystal Filter; FI711a/b) to suppress out-of-band signals. The converted 1st IF signal level is adjusted at PIN attenua- tors (D5
49、31D533, D535 or D631D632, D635) controlled by the BAL controller for the dualwatch function. The signal is applied to the 1st IF amplifier (Q551 or Q651) and then com- bined at L653. The combined signal passes through the MCFs (FI711a/b) and PIN attenuator (D781, D783). The signal is amplified at the 1st IF amplifier (Q721). The amplified signal is then applied to the 2nd mixer circuit. 3-1-6 2ND MIXER CIRCUIT (RF UNIT) The 2nd mixer circuit mixes the amplified 1st IF signal and 2nd LO signal (64.00 MHz) for conversion into the 2nd IF
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