IC-78_serv.pdf

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1、S-13707MZ-C1 2000 Icom Inc.1-1-32, Kamiminami, Hirano-ku, Osaka 547-0003, Japan Count on us! HF TRANCEIVER iC-78 iC-78 UPIC-78 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 sou

2、rce. 3. DO NOT force any of the variable components. Turn them slowly and smoothly. 4. DO NOT short any circuits or electronic parts. An insulated tuning tool MUST be used for all adjustments. 5. DO NOT keep power ON for a long time when the transceiver is defective. 6. DO NOT transmit power into a

3、signal generator or a sweep generator. 7. ALWAYS connect a 50 dB or 60 dB attenuator between the transceiver and a deviation meter or spectrum analyser when using such test equipment. 8. READ the instructions of test equipment thoroughly before connecting equipment to the transceiver. To upgrade qua

4、lity, all electrical or mechanical parts and internal circuits are subject to change without notice or obligation. 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

5、 liq- uids. DO NOT reverse the polarities of the power supply when connecting the transceiver. DO NOT apply an RF signal of more than 20 dBm (100 mW) to the antenna connector. This could damage the transceivers front end. ORDERING PARTS Be sure to include the following four points when ordering repl

6、acement parts: 1. 10-digit order numbers 2. Component part number and name 3. Equipment model name and unit name 4. Quantity required 1110004080 S.ICPC2709TIC-78 MAIN UNIT 1 piece 8810009130 Screw PH B0 M3 12 NI-ZU IC-78 CHASSIS6 pieces Addresses are provided on the inside back cover for your conven

7、ience. INTRODUCTION This service manual describes the latest service information for the IC-78 HF TRANSCEIVER at the time of publication. Commercial Commercial (w/alarm) Marine Marine (w/alarm) OTH OTH-1 OTH-2 OTH-3 #01 #02 #03 #04 SYMBOLVERSIONVERSION NO. 1-1-32, Kamiminami, Hirano-ku, Osaka 547-00

8、03, Japan Phone : 06 6793 5302 Fax: 06 6793 0013 URL: http:/www.icom.co.jp/world/index.html Communication Equipment Himmelgeister Str. 100, D-40225 Dsseldorf, Germany Phone: 0211 346047Fax : 0211 333639 URL: Unit 9, Sea St., Herne Bay, Kent, CT6 8LD, U.K. Phone: 01227 741741 Fax : 01227 741742 URL:

9、http:/www.icomuk.co.uk Zac de la Plaine, Rue Brindejonc des Moulinais BP 5804, 31505 Toulouse Cedex, France Phone: 561 36 03 03Fax : 561 36 03 00 URL: http:/www.icom- Crta. de Gracia a Manresa Km. 14,750 08190 Sant Cugat del Valles Barcelona, SPAIN Phone: (93) 590 26 70 Fax : (93) 589 04 46 URL: 238

10、0 116th Avenue N.E., Bellevue, WA 98004, U.S.A. Phone: (425) 454-8155Fax : (425) 454-1509 URL: Phone: (425) 454-7619 Glenwood Centre #150-6165 Highway 17 Delta, B.C., V4K 5B8, Canada Phone: (604) 952-4266Fax : (604) 952-0090 URL: A.B.N. 88 006 092 575 290-294 Albert Street, Brunswick, Victoria, 3056

11、, Australia Phone: 03 9387 0666Fax : 03 9387 0022 URL: .au 6F No. 68, Sec. 1 Cheng-Teh Road, Taipei, Taiwan, R.O.C. Phone: (02) 2559 1899Fax : (02) 2559 1874 TABLE OF CONTENTS SECTION 1 SPECIFICATIONS SECTION 2INSIDE VIEWS SECTION3 DISASSEMBLY INSTRUCTIONS SECTION 4CIRCUIT DESCRIPTION 4 1 RECEIVER C

12、IRCUITS . 4 1 4 2 TRANSMITTER CIRCUITS . 4 4 4 3 PLL CIRCUIT . 4 6 4 4 LOGIC CIRCUITS . 4 6 4 5 POWER SUPPLY CIRCUITS . 4 8 SECTION 5ADJUSTMENT PROCEDURES 5 1 PREPARATION BEFORE SERVICING. 5 1 5 2 PLL ADJUSTMENT . 5 2 5 3 TRANSMITTER ADJUSTMENTS. 5 4 5 4 RECEIVER ADJUSTMENTS. 5 8 5 5 SET MODE ADJUST

13、MENT. 5 10 SECTION 6PARTS LIST SECTION 7 MECHANICAL PARTS AND DISASSEMBLY SECTION 8SEMI-CONDUCTOR INFORMATIONS SECTION 9 BOARD LAYOUTS 9 1 MAIN UNIT . 9 1 9 2 PA UNIT. 9 3 9 3 PLL UNIT . 9 3 9 4 LOGIC UNIT . 9 5 9 5 PHONE BOARD. 9 5 9 6 MIC BOARD . 9 5 9 7 VR BOARD. 9 5 9 8 SENSOR BOARD. 9 6 9 9 FIL

14、TER UNIT. 9 7 SECTION 10 BLOCK DIAGRAM SECTION 11 WIRING DIAGRAM SECTION 12 VOLTAGE DIAGRAMS SECTION 1SPECIFICATIONS 1 - 1 I GENERAL Frequency coverage: Receive0.03029.999999 MHz*1 Transmit1.60029.999999 MHz*2 *1Guaranteed range: 0.529.999999 MHz *2Guaranteed range: 1.6001.999999 MHz 3.5003.999999 M

15、Hz 5.0007.999999 MHz 10.00029.999999 MHz Mode: USB, LSB, CW, AM, RTTY (FSK) Channel: 100 channel Frequency stability: Less than 200 Hz from 1 min. to 60 min. after power ON. After that rate of stability less than 30 Hz/hr at +25C (+77F). Temperature fluctuations 0C to 50C (+32F to +122F) less than 3

16、50 Hz. Power supply requirement: 13.8 V DC 15 % (negative ground) Current consumption: Transmitmax. power20.0 A Receivestand-by1.3 A max. audio2.0 A Usable temp. range: 10C to +60C (14F to 140F) Antenna connector: SO-239 (50 ) Dimensions: 240 (W) 95(H) 239(D) mm (projection not included)9716(W) 334(

17、H) 91332(D) in Weight: 3.8 kg (8 lb 6 oz) ACC connector: 13-pin REMOTE connector: 2-conductor 3.5(d) mm (18) I TRANSMITTER Modulation system: SSBBalanced modulation AMLow level modulation Output power: SSB/CW/RTTY/FM2100 W AM240 W Spurious emission: Less than 46 dB below peak out- put power * spurio

18、us frequency ; below 30 MHz: 50 dB, above 30 MHz: 60 dB Carrier suppression: More than 40 dB Unwanted sideband suppression: More than 50 dB Mic. connector: 8-pin connector (600 ) KEY connector: 3-conductor 6.5(d) mm (14) SEND connector: Phono (RCA) ALC connector: Phono (RCA) I RECEIVER Receive syste

19、m: Double-conversion superheterodyne Sensitivity (10 dB S/N): SSB, CW, RTTY0.16 V*1(1.829.999999 MHz) AM13 V (0.51.599999 MHz) 2.0 V*1(1.629.999999 MHz) *1Pre-amp 1 ON Squelch sensitivity: Less than 5.6 V (SSB) Selectivity: SSB, CW, RTTYMore than 2.1 kHz/6 dB Less than 4.5 kHz/60 dB AM More than 6.0

20、 kHz/6 dB Less than 20.0 kHz/40 dB Spurious and image rejection ratio: More than 70 dB (1.629.999999 MHz) Audio output power: More than 2.0 W (at 13.8 V DC)at 10 % distortion with an 8 load RIT variable range: 1200 Hz PHONES connector: 3-conductor 6.5(d) mm (14) EXT SP connector: 2-conductor 3.5(d)

21、mm (18) 8 All stated specifications are subject to change without notice or obligation. 2 - 1 SECTION 2INSIDE VIEWS Filter unitPA unit MAIN unit PLL unit Top view (PA AND FILTER UNITS) Bottom view (MAIN AND PLL UNITS) Rx RF preamplifier (Q1401, Q1402: 2SK2171) Tx mixer (Q101, Q102: 3SK131) 1st LO am

22、plifier (Q201: 2SC4673) Rx 1st mixer circuit (64.455 MHz) DDS gate allay IC (IC6: SC-1246A) Reference oscillator circuit (Q9: 2SC2714, X1: CR-337, 32.000 MHz) +5V Reg. (IC1: TA7805) BFO DDS (IC2: SC-1287) Rx 1st IF amplifier (Q1201: 3SK131) 2nd mixer circuit (D401: HSB88WSTR, Rx; 455 kHz, Tx; 64.455

23、 kHz) Predrive amplifier (Q1: 2SC1971) Tx/Rx switching relay (RL13: AG201344) Drive amplifier (Q2, Q3: 2SC3133) Power amplifier (Q4, Q5: 2SC2904) Tx 1st IF amplifier (Q151: 2SK882) MIC amplifier (IC2201: PC5023) Balanced modulator Tx 455 kHz Modulator (IC2301: NJM1496V) USB, LSB, CW, RTTY filter (FI

24、611: FL-65) Rx 2nd IF amplifier (Q1301: 3SK131) Tx 2nd IF amplifier (Q502: 2SK882) FAN control-2 (Q3601: 2SD1664) FAN control-1 (IC2101: NJM2058M) SWR detector (L13: LR-391 D2, D3: 1SS375) Tx low-pass filters 3 - 1 SECTION 3DISASSEMBLY INSTRUCTIONS Removing the covers Remove 14 screws from the top a

25、nd bottom covers. Removing the Front unit and PA cover Remove 4 screws from the front panel. Remove 5 screws from the PA cover. How to connect the coaxial cable Connect the coaxial cable as shown below. J6 J3 to MAIN unit PA unit FILTER unit J1 J701 PA cover FRONT panel MAIN unit PLL unit J3 from FI

26、LTER unit J6 from PA unit J701 J1 SECTION 4CIRCUIT DESCRIPTION 4 - 1 4-1 RECEIVER CIRCUITS 4-1-1 RF SWITCHING CIRCUIT (FILTER AND MAIN UNITS) The RF switching circuit leads receive signals to bandpass filters from the antenna connector while receiving. While transmitting, this circuit leads signals

27、from the RF power amplifier to the antenna connector. This circuit includes a 20 dB RF attenuator circuit to prevent distortion from very strong signals. RF signals from the antenna connector pass through the transmit/receive switching relay (RL13), and low-pass filter (L14, C14C16), and are then ap

28、plied to the MAIN unit via J3 (MAIN unit; J701). The signals from the FILTER unit are either bypassed or are attenuated at the 20 dB attenuator (D701, R703). The sig- nals are then applied to RF filters. 4-1-2 RF BANDPASS FILTER CIRCUIT (MAIN UNIT) RF bandpass filters pass only the desired band sign

29、als and suppress any undesired band signals. The RF circuit has 7 RF bandpass filters (BPF) for signals above 1.6 MHz and 1 low-pass filter (LPF) for signals and suppress any undesired band signals. (1) 0.031.6 MHz The signals pass through the low-pass filter (L821, L822, C822C824) to suppress unwan

30、ted frequencies. The fil- tered signals are bypassed a pre-amplifier by a BPF control signal (B0) and preamp control signal (PROF), and are then applied to the 1st mixer circuit (Q1101Q1104). (2) 1.62.0 MHz The signals pass through a bandpass filter (L831L833, L835, L836, C831C834, C837C840) to supp

31、ress unwant- ed frequencies. The filtered signals are then applied to the pre-amplifier circuit. (3) 2.030.0 MHz The signals pass through a high pass filter (L811L814, C811C817) to suppress excessively strong signals below 2.0 MHz, such as from broadcasting stations. The filtered signals are applied

32、 to a low-pass filter or one of 5 bandpass filters depending on their frequencies and are then applied to the pre-amplifier circuit. 4-1-3 PRE-AMPLIFIER CIRCUIT (MAIN UNIT) The pre-amplifier circuit uses two 2SK2171s to obtain 10 dB of gain over a wideband frequency range. When the pream- plifier is

33、 turned ON, the signals above 1.6 MHz are applied to the pre-amplifier circuit. Q1401 and Q1402 are connected in parallel to easily match the impedance to 50 . IC3003 (pins 11, 12) switches the signals from a bandpass filter, either to be bypassed, or to be applied to the pre-amplifier, depending on

34、 the PREAMP switch condition. Amplified or bypassed signals are applied to the 1st mixer circuit (Q1102Q1104) 4-1-4 1ST MIXER CIRCUIT (MAIN UNIT) The 1st mixer circuit mixes the receive signals with the 1st LO signal to convert the receive signal frequencies into a 64.455 MHz 1st IF signal. Used RF

35、filter Band 0.031.6 MHz 1.62 MHz 24 MHz 48 MHz Band 811 MHz 1115 MHz 1522 MHz 2230 MHz Control signal B4 B5 B6 B7 Control signal B0 B1 B2 B3 Input diode D80212 D80212 D803 D810 Input diode D804 D811 D805 D812 RECEIVER CONSTRUCTION ANT 1st mixer Q1101Q1104FI301A/BFI1301 BFO2nd LO1st LO Crystal filter

36、 2nd mixer D401IC2001 64.455 MHz SSB, CW, RTTY Ceramic BPF 455 kHz Ceramic BPF AF selector AM detector to AF amplifier SQL controll AM FI611 SSB-N, CW-N, RTTY-N (OPTION) Crystal BPF 4 - 2 The signals from the pre-amplifier circuit, or signals which bypass the pre-amplifier, pass through a low-pass f

37、ilter (L902, L903, C904C907). This low-pass filter suppresses signals above 30 MHz to eliminate direct receiving of signals at 64.455 MHz and image interference at 130160 MHz. The signals are then applied to the 1st mixer (Q1102Q1104). The 1st LO signal (64.48594.455 MHz) enters the MAIN unit from t

38、he PLL unit via J201 (PLL unit; J4). The LO signal is amplified at Q201 and then applied to the 1st mixer. The 1st mxer (Q1101Q1104) uses four 2SK1740s to pro- duce high level mixing with a high intercept point. 4-1-5 1ST IF CIRCUIT (MAIN UNIT) The 1st IF circuit filters and amplifies the 1st IF sig

39、nals. The 1st IF signals from the 1st mixer circuit are applied to MCF (Monolithic Crystal Filter: Fl301) to suppress out-of-band signals. The passband width of FI301 is 7.5 kHz/6 dB. The filtered signals are applied to the 1st IF amplifier (Q1201). AGC voltage is supplied to the 2nd gate of Q1201.

40、4-1-6 2ND MIXER CIRCUIT (MAIN UNIT) The 2nd mixer circuit mixes the amplified 1st IF signals and 2nd LO signal (64.00 MHz) to convert the 1st IF signals into a 2nd IF signal. The amplified 1st IF signals from Q1201 are converted into 455 kHz 2nd IF signal at the 2nd mixer (D401). D401 is a DBM (Doub

41、le Balanced Mixer). The 2nd LO level is approx. 0 dBm. The 2nd IF signals are applied to FI1301 to suppress unde- sired signals such as the 2nd LO signal, and are then applied to the NB circuit. 4-1-7 NOISE BLANKER CIRCUIT (MAIN UNIT) The noise blanker circuit detects pulse type noise, and turns OFF

42、 the signal line when noise appears. The 2nd IF signals from FI1301 are applied to the noise blanker gate (D1301, D1302). A portion of the signals from FI1301 is amplified at the noise amplifiers (Q1501, Q1502, Q1503), then detected at the noise detector (D1501). The detected signal from the noise detector is applied to the noise blanker control (Q150