Icom IC-78 Service Manualvice Man
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Icom IC-78 Service Manualvice Man

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HF TRANCEIVER
iC-78

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Summary of Contents for Icom IC-78

  • Page 1 HF TRANCEIVER iC-78...
  • Page 2 This service manual describes the latest service information NEVER connect the transceiver to an AC outlet or to a DC for the IC-78 HF TRANSCEIVER at the time of publication. power supply that uses more than 16 V. This will ruin the transceiver.

  • Page 3: Table Of Contents

    TABLE OF CONTENTS SECTION 1 SPECIFICATIONS SECTION 2 INSIDE VIEWS SECTION 3 DISASSEMBLY INSTRUCTIONS SECTION 4 CIRCUIT DESCRIPTION 4 – 1 RECEIVER CIRCUITS ......................... 4 – 1 4 – 2 TRANSMITTER CIRCUITS ......................4 – 4 4 – 3 PLL CIRCUIT ..........................4 – 6 4 –...

  • Page 4: Specifications

    SECTION 1 SPECIFICATIONS GENERAL RECEIVER • Frequency coverage • Receive system : Double-conversion Receive 0.030–29.999999 MHz* superheterodyne Transmit 1.600–29.999999 MHz* • Sensitivity (10 dB S/N) Guaranteed range: 0.5–29.999999 MHz SSB, CW, RTTY 0.16 µV* (1.8–29.999999 MHz) Guaranteed range: 1.600–1.999999 MHz 13 µV (0.5–1.599999 MHz) 3.500–3.999999 MHz 2.0 µV*...

  • Page 5: Inside Views

    SECTION 2 INSIDE VIEWS ¡Top view (PA AND FILTER UNITS) PA unit Filter unit Predrive amplifier (Q1: 2SC1971) Tx/Rx switching relay (RL13: AG201344) SWR detector Drive amplifier (L13: LR-391 (Q2, Q3: 2SC3133) D2, D3: 1SS375) Power amplifier (Q4, Q5: 2SC2904) Tx low-pass filters ¡Bottom view (MAIN AND PLL UNITS) 2nd mixer circuit...

  • Page 6: Disassembly Instructions

    SECTION 3 DISASSEMBLY INSTRUCTIONS • Removing the covers • How to connect the coaxial cable Remove 14 screws from the top and bottom covers. Connect the coaxial cable as shown below. J701 to MAIN unit PA unit FILTER unit • Removing the Front unit and PA cover PLL unit Remove 4 screws from the front panel.

  • Page 7: Circuit Description

    SECTION 4 CIRCUIT DESCRIPTION 4-1 RECEIVER CIRCUITS (3) 2.0–30.0 MHz The signals pass through a high pass filter (L811–L814, 4-1-1 RF SWITCHING CIRCUIT C811–C817) to suppress excessively strong signals below (FILTER AND MAIN UNITS) 2.0 MHz, such as from broadcasting stations. The filtered The RF switching circuit leads receive signals to bandpass signals are applied to a low-pass filter or one of 5 bandpass filters from the antenna connector while receiving.
  • Page 8 2nd LO signal, and are then applied to the NB circuit. BFO (Beat Frequency Oscillator) frequency is used at the SSB/CW detector and the balanced modulator. The IC-78 • Exact 2nd IF frequency uses a DDS IC for the BFO circuit.
  • Page 9 4-1-10 SSB/CW DEMODULATOR CIRCUITS When the strong signal disappears, C1804 and R1809 release the AGC line voltage in CW or RTTY mode to obtain (MAIN UNIT) a fast AGC release time. While in SSB or AM mode, C1803, In SSB or CW mode, the 2nd IF signal from the IF amplifier C1805, R1808 and C1802, R1807 are connected in parallel (Q1601) is mixed with the BFO signal from the PLL unit at to obtain a appropriate AGC characteristics (middle or slow...

  • Page 10: Transmitter Circuits

    R3703 determines the The ALC (Automatic Level Control) circuit controls the gain transmit delay timing. of IF amplifiers in order for the IC-78 to output a constant RF power set by the [RF PWR] control even when the supplied voltage shifts, etc.
  • Page 11 The “FOR” voltage from the FILTER unit is applied to For the current APC, the power transistor current is obtained IC1701c (pin 9) in the MAIN unit. The “POCV” voltage from by detecting the voltage (“ICH” and “ICL”) which appear at both terminals of a 0.012 Ω...

  • Page 12: Pll Circuit

    4-3 PLL CIRCUITS 4-4 LOGIC CIRCUITS 4-3-1 GENERAL DESCRIPTION 4-4-1 BAND SELECTION DATA (MAIN UNIT) The PLL unit contains 2 DDS circuits for generating a 1st LO To select the correct bandpass filter and low-pass filter, the signal (64.485–94.455 MHz variable) and a BFO frequency CPU outputs the following band selection data from the I/O (453.5–456.5 kHz).
  • Page 13 Outputs chip select signal for EEP- stored in the EEPROM (IC2). ROM (IC2). Input port for serial signal from EEP- The Icom CI-V network system allows the IC-78 to be ROM (IC2). remotely controlled by a personal computer using an RS- 232C I/O port.

  • Page 14: Power Supply Circuits

    4-5 POWER SUPPLY CIRCUITS 4-5-1 PA UNIT LINE DESCRIPTION The voltage from an external power supply passed through a fuse (F1). The same voltage as the HV line passed through 14 V the switching relay (RL1). 4-5-2 LOGIC UNIT LINE DESCRIPTION Common 5 V converted from the HV line and regulated by the H5V regulator circuit (IC5).

  • Page 15: Adjustment Procedures

    RF power meter the antenna connector. to [DC 13.8 V] DC power supply Ammeter to [EXT SP] Distortion meter Speaker • Microphone connector (Front panel view) IC-78 Audio generator Pin 1 Pin 7 Pin 6 Pin 5 5 - 1...

  • Page 16: Pll Adjustment

    5-2 PLL ADJUSTMENTS ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST Turn L6, L7 on the PLL unit to downside for REFERENCE • Display frequency: Any Connect a frequency presetting until the frequency counter reads FREQUENCY • Set C16 as illustration at below. counter check frequency.
  • Page 17 • PLL unit 2nd LO check point Reference frequency check point Reference OSC level adjustment Reference freauency Reference adjustment frequency pre-setting 1st LO 1st LO output level check point C165 VCO lock voltage adjustment 5 - 3...

  • Page 18: Transmitter Adjustments

    • Mode : USB (3 A) between power Tx current Increases • RF power : Minimum (L) supply and the IC-78. 200 mA. (for driver) • Mic gain : Minimum (0) • Disconnect J3601 (MAIN unit) and preset R21, R24 (PA unit) to max.
  • Page 19 • PA unit • FILTER unit SWR detector check point Idling current adjustment SWR detector (Driver) pre-setting SWR detector Idling current adjustment adjustment (Final) • MAIN unit CP4002 Ic APC pre-setting L106 L151 L301 L302 Tx total gain L303 adjustment L501 R503 J3601...
  • Page 20 TRANSMITTER ADJUSTMENTS—continued ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST CARRIER • Display frequency: 12.23000 MHz Rear Connect a spectrum Minimum carrier level MAIN R2303 SUPPRESSION • Mode : USB panel analyzer to the [ANT] • Mic gain : Minimum (0) connector through an •...
  • Page 21 • MAIN unit CP3701 CW carrier check point R2303 Carrier suppression adjustment R2321 AM modulation adjustment (or AM carrier pre-setting) R3703 CW carrier adjustment R2385 AM modulation adjustment R1730 (or AM carrier pre-setting) AM carrier adjustment 5 - 7...

  • Page 22: Receiver Adjustments

    5-4 RECEIVER ADJUSTMENTS Receiver total gain adjustment must perform after transmitter total gain adjustment. ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST RECEIVER • R2701 (MAIN unit): Center Rear Connect an AC milli- Maximum audio output MAIN Adjust in ˚...
  • Page 23 • MAIN unit L1103 L1201 L1202 L1502 Noise blanker adjustment L1501 Rx total gain adjustment CP1501 Noise blanker check point L1621 L1614 R2701 Rx total gain pre-setting 5 - 9...

  • Page 24: Set Mode Adjustment

    5-5 SET MODE ADJUSTMENT ADJUSTMENT ADJUSTMENT CONDITION DISPLAY OPERATION • Enter set mode adjustment for RX: Push [SET] key to enter the RX set- ENTERING ting. SET MODE 1 Turn power OFF. ADJUSTMENT 2 Terminate the [REMOTE] jack with a Or push [UP] key to skip the set FOR RX 3.5(d) mm mini-plug.
  • Page 25 SET MODE ADJUSTMENT —continued ADJUSTMENT ADJUSTMENT CONDITION DISPLAY OPERATION • Connect a 50 Ω dummy load or power Transmit using an external PTT SWR METER meter to [ANT] connector. switch to set SWR reference level after pushing [SET]. • Connect a 100 Ω dummy load or power Transmit using an external PTT meter to [ANT] connector.

  • Page 26: Front Unit

    8900006990 CABLE OPC-683 (N:10 L:110) 6200003260 S.COIL NL 322522T-101J 6200002040 S.COIL NL 252018T-101J 6200002040 S.COIL NL 252018T-101J 8970023720 E.OTHER SX2241 ICOM SHIELD (1) /FR 6200003950 S.COIL HF50ACC 322513-T 6200009300 S.COIL ELJPA 100KF 10U 6200003950 S.COIL HF50ACC 322513-T 6450001230 E.OTHER HLJ0999-01-480 6200003950 S.COIL...

  • Page 27: Logic Board

    [LOGIC BOARD] [LOGIC BOARD] ORDER ORDER DESCRIPTION DESCRIPTION R103 7030003590 S.RESISTOR ERJ3GEYJ 183 V (18 kΩ) 4510004630 S.ELECTROLYTIC ECEV1CA100SR R104 7030003540 S.RESISTOR ERJ3GEYJ 682 V (6.8 kΩ) 4030011600 S.CERAMIC C1608 JB 1C 104KT-N R105 7030003620 S.RESISTOR ERJ3GEYJ 333 V (33 kΩ) 4510004440 S.ELECTROLYTIC ECEV1HA010SR R106 7030003640 S.RESISTOR...

  • Page 28: Main Unit

    [VR BOARD] [MAIN UNIT] ORDER ORDER DESCRIPTION DESCRIPTION 7210003040 VARIABLE TP96D26-22F-10KBX2-2240 1110004080 S.IC µPC2709T-E3 7210003030 VARIABLE TP96D00-22F-10KBX2-2240 IC1701 1110003870 S.IC NJM2058M-T1 7030003540 S.RESISTOR ERJ3GEYJ 682 V (6.8 kΩ) IC1751 1110002700 S.IC NJM2904M-T1 IC2001 1110004870 S.IC TA4101F (TE12L) IC2101 1110003870 S.IC NJM2058M-T1 6510022050 S.CONNECTOR 10FM-1.0SP-1.9-TF...
  • Page 29 [MAIN UNIT] [MAIN UNIT] ORDER ORDER DESCRIPTION DESCRIPTION D302 1790000620 S.DIODE MA77 (TX) L104 6200003260 S.COIL NL 322522T-101J D303 1790000620 S.DIODE MA77 (TX) L105 6140003210 S.COIL LR-358 D304 1790000620 S.DIODE MA77 (TX) L106 6150004270 COIL LS-483A (C-14924) D305 1790000620 S.DIODE MA77 (TX) L151 6150004280 COIL...
  • Page 30 [MAIN UNIT] [MAIN UNIT] ORDER ORDER DESCRIPTION DESCRIPTION L2901 6140002220 COIL LR-270 (TR6X3X2 3A9) R631 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 kΩ) L3501 6180000960 COIL LAL 03NA 102K R632 7030003530 S.RESISTOR ERJ3GEYJ 562 V (5.6 kΩ) L3502 6180000960 COIL LAL 03NA 102K R633 7030003440 S.RESISTOR ERJ3GEYJ 102 V (1 kΩ)
  • Page 31 [MAIN UNIT] [MAIN UNIT] ORDER ORDER DESCRIPTION DESCRIPTION R1520 7030003540 S.RESISTOR ERJ3GEYJ 682 V (6.8 kΩ) R2102 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 kΩ) R1521 7030003440 S.RESISTOR ERJ3GEYJ 102 V (1 kΩ) R2103 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 kΩ) ERJ3GEYJ 221 V (220 Ω) R1522 7030003360 S.RESISTOR...
  • Page 32 [MAIN UNIT] [MAIN UNIT] ORDER ORDER DESCRIPTION DESCRIPTION R3002 7030003640 S.RESISTOR ERJ3GEYJ 473 V (47 kΩ) C102 4030007090 S.CERAMIC C1608 CH 1H 470J-T-A R3003 7030003640 S.RESISTOR ERJ3GEYJ 473 V (47 kΩ) C103 4030007150 S.CERAMIC C1608 CH 1H 151J-T-A R3004 7030003640 S.RESISTOR ERJ3GEYJ 473 V (47 kΩ) C104 4030007050 S.CERAMIC...
  • Page 33 [MAIN UNIT] [MAIN UNIT] ORDER ORDER DESCRIPTION DESCRIPTION C843 4030007100 S.CERAMIC C1608 CH 1H 560J-T-A C1507 4030011600 S.CERAMIC C1608 JB 1C 104KT-N C844 4030009580 S.CERAMIC C1608 JB 1H 681K-T-A C1508 4030010760 S.CERAMIC C1608 CH 1H 331J-T-A C845 4030010040 S.CERAMIC C1608 JB 1H 561K-T-A C1509 4030011600 S.CERAMIC C1608 JB 1C 104KT-N...
  • Page 34 [MAIN UNIT] [MAIN UNIT] ORDER ORDER DESCRIPTION DESCRIPTION C2309 4030011600 S.CERAMIC C1608 JB 1C 104KT-N C4104 4030006880 S.CERAMIC C1608 JB 1H 472K-T-A C2310 4030011600 S.CERAMIC C1608 JB 1C 104KT-N C4105 4030006880 S.CERAMIC C1608 JB 1H 472K-T-A C2312 4510005810 S.ELECTROLYTIC ECEV1HAR47R C4106 4030006880 S.CERAMIC C1608 JB 1H 472K-T-A...

  • Page 35: Pll Unit

    [MAIN UNIT] [PLL UNIT] ORDER ORDER DESCRIPTION DESCRIPTION J4201 6510021720 S.CONNECTOR 30FLT-SM1-TB 6170000230 COIL LW-25 J4401 6510021720 S.CONNECTOR 30FLT-SM1-TB 6170000230 COIL LW-25 J4501 6450000140 CONNECTOR HSJ0807-01-010 6200001830 S.COIL NL 322522T-100J J4502 6510018960 S.CONNECTOR B2B-PH-SM3-TB 6200003050 S.COIL NL 322522T-R82J-3 J4651 6450001640 CONNECTOR TCS5044-01-4111 6200003430 S.COIL NL 322522T-R10J...
  • Page 36 [PLL UNIT] [PLL UNIT] ORDER ORDER DESCRIPTION DESCRIPTION 7030003440 S.RESISTOR ERJ3GEYJ 102 V (1 kΩ) 4030009500 S.CERAMIC C1608 CH 1H 0R5B-T-A 7030003440 S.RESISTOR ERJ3GEYJ 102 V (1 kΩ) 4030007030 S.CERAMIC C1608 CH 1H 150J-T-A 7030003440 S.RESISTOR ERJ3GEYJ 102 V (1 kΩ) 4030007400 S.CERAMIC C1608 PH 1H 121J-T-A ERJ1WYJ220U (22 Ω)
  • Page 37 ERT-D2FHL 333S 8970023701 E.OTHER SX2241 0.8D COAXIAL TUBE (2)/PL 7030003470 S.RESISTOR ERJ3GEYJ 182 V (1.8 kΩ) ERJ1WYJ100U (10 Ω) 8970023710 E.OTHER SX2241 ICOM SHIELD (1) /PL 7030006130 S.RESISTOR ERJ1WYJ100U (10 Ω) 7030006130 S.RESISTOR ERJ1WYJ3R3U (3.3 Ω) 7030008000 S.RESISTOR ERJ1WYJ3R3U (3.3 Ω)

  • Page 38: Filter Unit

    [PA UNIT] [FILTER UNIT] ORDER ORDER DESCRIPTION DESCRIPTION 4030005050 S.CERAMIC C2012 CH 1H 331J-T-A L104 6200005010 S.COIL NL 252018T-100J 4030011550 S.CERAMIC GRM42-6 CH 680J 500PT L105 6200005050 S.COIL NL 252018T-330J 4030014460 S.CERAMIC GRM42-6 CH 820J 500PT 4030011760 S.CERAMIC GRM44-1 SL 682J 200PT 4030011760 S.CERAMIC GRM44-1 SL 682J 200PT 7540000100 ABSORBER...
  • Page 39 4030006880 S.CERAMIC C1608 JB 1H 472K-T-A 4030006880 S.CERAMIC C1608 JB 1H 472K-T-A 4030006880 S.CERAMIC C1608 JB 1H 472K-T-A 2710000520 FAN SB0812H-ICOM-00 4030006880 S.CERAMIC C1608 JB 1H 472K-T-A 4030006880 S.CERAMIC C1608 JB 1H 472K-T-A 4030014460 S.CERAMIC GRM42-6 CH 820J 500PT 8900009501 CABLE...

  • Page 40: Logic Unit

    DESCRIPTION QTY. REF NO. DESCRIPTION QTY. 6510000370 ANT connector MR-DS 2510000670 Speaker VS-50-0827 2710000520 Fan SB0812H-ICOM-00 6450001230 Snap plate HLJ0999-01-480 8930021010 Domed plug DP-500 8210016620 2241 front panel 6910000310 B312D insulation washer 8930050940 2241 21-key 6910000340 P101 KD insulation sheet...
  • Page 41 MP22 (C) MP22 (C) MP33 (C) MP34 (C) MP35(C) MP34 (C) MP2 (C) MP1 (L) MP22 (C) MP14 (C) MP20 (C) MP3 (L) MP22 (C) MP20 (C) EP2 (C) EP3 (C) MP20 (C) EP70 (L) MP15 (C) MP14 (C) MP26 (C) MP14 (C) MP22 (C) MP23 (F)
  • Page 42 SECTION SECTION 8 PARTS LIST SEMI-CONDUCTOR INFORMATIONS 8-1 TRANSISTORS 8-2 DIODES NAME SYMBOL INSIDE VIEW NAME SYMBOL INSIDE VIEW NAME SYMBOL INSIDE VIEW NAME SYMBOL INSIDE VIEW 2SA1576A R 2SK882-GR 1SS184 MA29B DAN202K 2SC1971 None 2SK2171-4 1SS226 2SC3133 None 1SS375-TL MA77 DA221 TL MA742...

  • Page 43: Main Unit

    SECTION 9 BOARD LAYOUTS 9-1 MAIN UNIT • TOP VIEW J4651 The combination of this page and the next page shows to FILTER unit J3 to PA unit J6 the unit layout in the same configuration as the actual P.C. Board. to FILTER unit J1 SEND T13V...
  • Page 44 J4651 • BOTTOM VIEW (MAIN UNIT) SEND 13.8V The combination of this page and the previous page shows the unit layout in the same configuration as the SEND J4801 ALC J4801 actual P.C. Board. SQLS EXT SP J4501 FSKK ELEC-KEY J5101 REMOTE J5001 BAND ESPO...

  • Page 45: Pll Unit

    9-3 PLL UNIT 9-2 PA UNIT • TOP VIEW • TOP VIEW 2nd LO to MAIN unit J401 PLL WS2 to MAIN unit J2001 BFOE 2LOE 2LOE FILTER unit J2 CHASSIS to MAIN unit PSTB DSTB PDAT CON2 PLL WS1 CON1 CON0 FSKK...
  • Page 46 The combination of this page and the previous page shows the unit layout in the same configuration as the actual P.C. Board. • BOTTOM VIEW (PLL UNIT) • BOTTOM VIEW (PA UNIT) VARISTOR BOARD 9 - 4...

  • Page 47: Logic Unit

    The combination of this page and the next page shows 9-4 LOGIC BOARD The combination of this page and the next page the unit layout in the same configuration as the actual shows the unit layout in the same configuration as •...

  • Page 48: Sensor Board

    The combination of this page and the previous page The combination of this page and the previous page shows the unit layout in the same configuration as the shows the unit layout in the same configuration as actual P.C. Board. the actual P.C.

  • Page 49: Filter Unit

    9-9 FILTER UNIT • TOP VIEW The combination of this page and the next page to PA unit J7 shows the unit layout in the same configuration as to MAIN unit J701 the actual P.C. Board. CHASSIS 2 4 6 8 10 1 3 5 7 9 ANTENNA to MAIN unit J4001...
  • Page 50 The combination of this page and the previous page shows the unit layout in the same configuration as the actual P.C. Board. • BOTTOM VIEW (FILTER UNIT) 9 - 8...

  • Page 51: Block Diagram

    SECTION 10 BLOCK DIAGRAM below 1.6 M Q1508 2SC4081 Q1509 DTA114 GATE IC2701 IC2101A CTRL 1.6–2 M NJM2058 M5282FP Q1503 Q1502 Q1501 D1501 AFGV 1SS375 2SK882 2SK882 2SK882 Q1506 Q1507 DTC114 2SC4081 SIDE TONE/BEEP/TONE NOISE NOISE NOISE 2–4 M MAIN UNIT IC5601 LEVEL IC2702...

  • Page 52: Wiring Diagram

    SECTION 11 WIRING DIAGRAM CHASSIS FRONT UNIT LOGIC J4401 STRT STRT UNIT SNDS SNDS J4101 FSKK FSKK MICE MICE STAR SENSOR SEND SEND BOARD SQLS SQLS SEND SEND PA UNIT SEND SEND PAT8 PAT8 SEND SEND ASC2 SEN1 SEN1 PHOE PHOE SEN2 STAR...

  • Page 53: Voltage Diagrams

    SECTION 12 VOLTAGE DIAGRAM PLL unit PLL unit WS1A WS1B CHASSIS PLL unit J4 PLL unit J1 – SB0812H-ICOM-00 1LOE 2LOE 12-1 FILTER, PA and MAIN units J3601 1st Lo 2nd Lo Tx: 0V J201 J401 Q511 Rx: 3.5V C511 AM ON: 0.6V...

  • Page 54: Pll Unit

    12-2 PLL and LOGIC units 1st Lo 7.9V 3.2V 10µH R191 180 C112 C114 0.1µH 82nH W103 W104 L40 100µH : 6.0V : 8.1V 3.9V MAIN Lo : 5.6V Lo : 11.0V unit 2SD1619 T C194 OFF: 4.4V OFF: 13.0V J201 0.0047 10µH...
  • Page 55 1-1-32, Kamiminami, Hirano-ku, Osaka 547-0003, Japan Phone : 06 6793 5302 : 06 6793 0013 : http://www.icom.co.jp/world/index.html < > Corporate Headquarters Communication Equipment 2380 116th Avenue N.E., Bellevue, WA 98004, U.S.A. Himmelgeister Str. 100, D-40225 Düsseldorf, Germany Phone : ( 425 ) 454-8155...
  • Page 56 Count on us! S-13707MZ-C1 1-1-32, Kamiminami, Hirano-ku, Osaka 547-0003, Japan © 2000 Icom Inc.

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