ICOM IC-7700 Service Repair Manual

S-14407XZ-C1 Feb. 2008 HF/50MHz TRANSCEIVER Downloaded from www.Manualslib.com manuals search engine

This service manual describes the latest service information for the IC-7700 HF/50MHz TRANSCEIVER at the time of publication. NEVER connect the transceiver to an AC outlet or to a DC power supply that uses more than specifed. 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 connecting the transceiver. DO NOT apply an RF signal of more than 20 dBm (100 mW) to the antenna connector. This could damage the transceiver’s front-end. To upgrade quality, any electrical or mechanical parts and internal circuits are subject to change without notice or obligation. MODEL VERSION IC-7700 USA EUR FRA ITR ESP UK KOR Be sure to include the following four points when ordering replacement parts: 1. 10-digit Icom parts numbers 2. Component name 3. Equipment model name and unit name 4. Quantity required <ORDER EXAMPLE> 1110003491 S.IC TA31136FNG IC-7700 MAIN UNIT 5 pieces 8820001210 Screw 2438 screw IC-7700 Top cover 10 pieces Addresses are provided on the inside back cover for your convenience. 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. ORDERING PARTS 1. Make sure the 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 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 Standard 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 Analyzer when using such test equipment. 8. READ the instructions of test equipment throughly before connecting a test equipment to the transceiver. REPAIR NOTES INTRODUCTION CAUTION Downloaded from www.Manualslib.com manuals search engine

CONTENTS SECTION 1 SPECIFICATIONS SECTION 2 INSIDE VIEWS SECTION 3 CIRCUIT DESCRIPITON 3-1 RECEIVER CIRCUITS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 3-2 TRANSMITTER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 3-3 FREQUENCY SYNTHESIZER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 3-4 MAIN CPU PORT ALLOCATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 SECTION 4 ADJUSTMENT PROCEDURES 4-1 PREPARATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 4-2 ADJUSTMENTS ON THE OSC UNIT AND PLL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 4-3 ADJUSTMENTS ON THE RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5 4-4 ADJUSTMENTS ON THE PA200W BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7 4-5 ADJUSTMENTS ON THE MAIN UNIT (including RF UNIT) . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9 4-6 ADJUSTMENTS ON THE SCOPE UNIT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11 4-7 AUTOMATIC ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12 SECTION 5 PARTS LIST SECTION 6 MECHANICAL PARTS SECTION 7 BOARD LAYOUTS SECTION 8 GENERAL WIRING SECTION 9 BLOCK DIAGRAM SECTION 10 SCHEMATIC DIAGRAM FRONT UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 LOGIC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2 MAIN UNIT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8 PLL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12 OSC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13 ANT-SW UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-16 DIGISEL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-16 RF UNIT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-17 NETWORK BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-22 CTRL BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-23 FILTER UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-24 PA200W BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-25 SCOPE UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-26 DC-DC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-29 Downloaded from www.Manualslib.com manuals search engine

1 - 1 SECTION 1 SPECIFICATIONS D General • Frequency coverage (unit: MHz) : Receiver 0.030000–60.000000* 1 Transmitter 1.800000–1.999999* 2 , 3.500000–3.999999* 2 , 5.330500* 3 , 5.346500* 3 , 5.366500* 3 , 5.371500* 3 , 5.403500* 3 , 7.000000–7.300000* 2 , 10.100000–10.150000* 2 , 14.000000–14.350000* 2 , 18.068000–18.168000* 2 , 21.000000–21.450000* 2 , 24.890000–24.990000* 2 , 28.000000–29.700000* 2 , 50.000000–54.000000* 2 * 1 Some frequency ranges are not guaranteed. * 2 Depending on versions. * 3 USA version only. • Operating mode : USB, LSB, CW, RTTY, PSK31, AM, FM • Number of memory channels : 101 (99 regular, 2 scan edges) • Antenna connector : SO-239×4 (antenna impedance: 50 ) • Operating temperature range : 0˚C to +50˚C; +32˚F to +122˚F • Frequency stability : Less than ±0.05 ppm (approx. 5 min. after from turn the main power, [I/O], ON, 0–50˚C; 32–122˚F) • Frequency resolution : 1 Hz • Power supply requirement : 85–265 V AC (universal input) • Power consumption : Receive Stand-by 200 VA typical Max. audio 210 VA typical Transmit at 200 W 800 VA • Dimensions (projections not included) : 425×149×437 mm; 16 23 /32×5 7 /8×17 7 /32 in • Weight : Approx. 22.5 kg; 50 lb • ACC 1 connectors : 8-pin DIN connector • ACC 2 connectors : 7-pin DIN connector • Display* : 7-inch (diagonal) TFT color LCD (800×480) • EXT-DISPLAY connector : D-sub 15S • CI-V connector : 2-conductor 3.5 (d) mm ( 1 /8 ) • RS-232C connector : D-sub 9-pin • USB connector : USB (Universal Serial Bus)1.1/2.0×2 D Transmitter • Transmit output power : SSB, CW, RTTY, PSK31, FM 5–200 W AM 5–50 W • Modulation system : SSB D.P.S.N. modulation AM Digital low power modulation FM Digital phase modulation • Spurious emission : Harmonics More than 60 dB (HF bands) More than 70 dB (50 MHz band) Unwanted emission More than 50 dB (HF bands) (except Harmonics) More than 66 dB (50 MHz band) Out of band emission More than 40 dB (HF bands) More than 60 dB (50 MHz band) • Carrier suppression : More than 63 dB • Unwanted side-band suppression : More than 80 dB • ∂TX variable range : ±9.999 kHz • Microphone connector : 8-pin connector (600 ) • ELEC-KEY connector : 3-conductor 6.35 (d) mm ( 1 /4 ) • KEY connector : 3-conductor 6.35 (d) mm ( 1 /4 ) • RELAY connector : Phono (RCA) • ALC connector : Phono (RCA) Downloaded from www.Manualslib.com manuals search engine

1 - 2 D Receiver • Receive system : Double conversion superheterodyne system • Intermediate frequencies : 1st 64.455 MHz 2nd 36 kHz • Sensitivity (typical) : SSB, CW, RTTY (BW=2.4 kHz, 10 dB S/N) 0.100000– 1.799999 MHz 0.5 μV (pre-amp 1 ON) 1.800000– 29.990000 MHz 0.16 μV (pre-amp 1 ON) 50.000000– 54.000000 MHz 0.13 μV (pre-amp 2 ON) AM (BW=6 kHz, 10 dB S/N) 0.100000– 1.799999 MHz 6.3 μV (pre-amp 1 ON) 1.800000– 29.990000 MHz 2 μV (pre-amp 1 ON) 50.000000– 54.000000 MHz 1 μV (pre-amp 2 ON) FM (BW=15 kHz, 12 dB SINAD) 28.000000– 29.990000 MHz 0.5 μV (pre-amp 1 ON) 50.000000– 54.000000 MHz 0.32 μV (pre-amp 2 ON) • Internal Modulate Distortion (typical) : Dynamic range 109 dB (at 14.100 MHz, 100 kHz separation, pre-amp OFF, CW mode; BW=500 Hz) • Selectivity : SSB, RTTY (BW=2.4 kHz) More than 2.4 kHz/–3 dB Less than 3.6 kHz/–60 dB CW (BW=500 Hz) More than 500 Hz/–3 dB Less than 700 Hz/–60 dB AM (BW=6 kHz) More than 6.0 kHz/–3 dB Less than 15.0 kHz/–60 dB FM (BW=15 kHz) More than 12.0 kHz/–6 dB Less than 20.0 kHz/–60 dB • Spurious and image rejection ratio : More than 70 dB • Squelch sensitivity (pre-amp OFF) : SSB, CW, RTTY, PSK31 Less than 5.6 μV FM Less than 1 μV • RIT variable range : ±9.999 kHz • Audio output power : More than 2.6 W at 10% distortion with an 8 load • PHONES connector : 3-conductor 6.35 (d) mm ( 1 /4 ) • EXT-SP connectors : 2-conductor 3.5 (d) mm ( 1 /8 )/8 D Antenna tuner • Matching impedance range : 16.7 to 150 unbalanced (HF bands; VSWR better than 3:1) 20 to 125 unbalanced (50 MHz band; VSWR better than 2.5:1) • Minimum operating input : 8W (HF bands) 15 W (50 MHz band) • Tuning accuracy : VSWR 1.5:1 or less • Insertion loss (after tuning) : Less than 1.0 dB All stated specifications are typical and subject to change without notice or obligation. Downloaded from www.Manualslib.com manuals search engine

2 - 1 SECTION 2 INSIDE VIEW (viewing from the bottom) RF UNIT OSC UNIT DIGISEL UNIT (under the cover) MAIN UNIT PLL UNIT SCOPE UNIT Downloaded from www.Manualslib.com manuals search engine

3 - 1 SECTION 3 CIRCUIT DESCRIPTION 3-1 RECEIVER CIRCUITS ANT-SW UNIT Antenna switching relays (RL51, 61, 71, 81) select the RX signals which are from [ANT1]–[ANT4], and the relays are controlled by relay controller (IC11). RX signals from [ANT1] –[ANT3] are applied to the CTRL BOARD, RX signals from [ANT4] are applied to the RF UNIT directly. CTRL BOARD The CTRL BOARD has TX/RX switch which toggles the RF path between in TX and RX. RX signals from the ANT-SW UNIT are passed through the TX/RX switches (RL252–254), and applied to the RF UNIT. RF UNIT RF UNIT contains receive circuits; from RX BPF to 2nd RX IF AMP. The RX signals are filtered by BPFs to remove unwanted signals and amplified, then down-converted twice into 2nd IF signal. The received signals from the ANT-SW UNIT and CTRL BOARD are passed through some relays and attenuators, then filtered by BPFs which is assigned to filter the RX signals that desired to receive. The filtered RX signals are amplified by RF AMPs before being applied to the 1st mixer. • 0.03–30 MHz SIGNALS The RX signals from the band SW (RL351) are passed though one of the BPF or LPF. The filtered signals are entered to the DIGISEL UNIT, and gone through or by-passed the DIGISEL (Digital RF Selector Switch) filter. When the DIGISEL function is activated, the RX signals are passed through the DIGISEL SW (RL21) and narrow bandwidth filter (D_SEL) which filters out unwanted signals with its sharpen frequency response. The filtered signals are amplified by the RF AMP (Q201) which recovers the insert loss of the D_SEL filter, then backed to the RF UNIT via DIGISEL SW (RL2). The RX signals from the DIGISEL UNIT are applied to or by-passed the Pre-AMP. When the Pre-AMP1/2 is activated, the RX signals are applied to the Pre-AMP1 (for all HF bands) or Pre-AMP2 (for 24 MHz and above) via P.AMP SW (RL1004), and the amplified RX signals are applied to the 1st mixer (IC1051) via the P.AMP SWs (RL1005, 1006) and LPF. The RX signals are mixed with the 1st LO signals from the PLL UNIT (1st LO signals are gone through LO AMPs (Q1105, 1104, 1101) before being applied.) to be converted into the 1st RX IF signal. • 30–60 MHz SIGNALS RX signals from the band SW (RL351) are passed though one of the BPFs (Fc=50–54 MHz or Fc=54–60 MHz) to remove unwanted signals. The filtered signals are amplified by one of (or both of) the Pre-AMPs (or by-passed; according to the setting). The amplified RX signals are then applied to the 1st mixer (Q1211, 1212) via the LPF. The RX signals are mixed with the 1st LO signals from PLL UNIT (the 1st LO signals are gone through LO AMP (Q1301), HPF and LPF before being applied.) to be converted into the 1st RX IF signal. A portion of 1st IF signal is applied to the SCOPE UNIT via buffer (Q1352). The converted 1st RX IF signal is then filtered by one of 1st IF filters on the MCF BOARDs (FI1401). Selecting of the filter to pass is carried out by IF SW (IC1402, 1403). The filtered 1st RX IF signal is amplified by two 1st IF AMPs (Q1401–1403), then splitted into two before being applied to the 2nd mixers; as a image rejection mixer (IC501, 1502). Each divided 1st RX IF signal is mixed with 2nd LO signals from the PLL UNIT (gone through ATT, LO AMP (Q1651), buffer (IC1651) and another buffer (IC1651)), to be converted into the 36 kHz 2nd RX IF signal. One of the LO signal is 90 degrees phase-shifted before being applied to the 2nd mixer (IC1502), and the converted 2nd RX IF is 90 degrees phase-shifted too. These converted 2nd RX IF signals are buffer-amplified by buffer (IC1502/IC1501) and amplified by 2nd IF AMP (IC1504/IC1503). Then the 2nd RX IF signals whose phase is different each other are phase-shifted by the phase shifter (IC1505), then composed by the composer (IC1505). The composed 2nd RX IF signal is amplified by another 2nd IF AMP (IC1506), then entered to the MAIN UNIT. Signal Frequency Signal Frequency 1st RX IF 64.455 MHz 1st RX LO 64.485–124.455 MHz 2nd RX IF 36 kHz 2nd RX LO 64.491 MHz 1st TX IF 36 kHz 1st TX LO 64.485–124.455 MHz 2nd TX IF 455 kHz 2nd TX LO 64 MHz 3rd TX IF (*) *; Refer to "SPECIFICATIONS." • FREQUENCY CONFIGURATION Downloaded from www.Manualslib.com manuals search engine

3 - 2 MAIN UNIT MIAN UNIT contains receive circuits; from demodulator to AF circuits. The 2nd IF signal is demodulated by digital audio processing circuits. • DEMODULATOR CIRCUIT The 36 kHz 2nd RX IF signal from the MAIN UNIT is applied to the Analog to Digital Converter (ADC; IC1251) via the IF mute SW (IC1201) and unbalance-balance convert circuit (IC1211, 1231), to be converted into the 24-bit serial data. The serial data is applied to the DSP (IC1001) and processed as digital audio signals. The processed digital audio signals are then applied to the Digital Audio Converter (DAC; IC1501) to be converted into the analog audio signals; as recovered AF signals. The recovered AF signals are applied to the RX AF circuits via buffer (IC1751). • RX AF CIRCUITS The recovered AF signals are amplified and level-adjusted, then output from the audio interfaces. (The destination of AF output signals is depends on the setting) <OUTPUT FROM Int./Ext. SPEAKER> The recovered AF signals from the buffer (IC1751) are passed through the SQL SW (Q351), and applied to the AF AMP (IC331). The amplified AF signals are splitted into two AF lines; one is bound for the headphones jack (J2) on the FRONT UNIT, another is bound for the internal speaker (SP1)/external speaker via the external SP jack (J751) on the MAIN UNIT. Both of AF signals on each AF lines are applied to the 2-channel Voltage Controlled Amplifier (VCA; IC311) whose gain is determined by applied control voltage to be adjusted its signal level. The level-adjusted AF signals are applied to the AF power AMP (IC281) which power-amplifies to obtain audio output power, via LPF (Q291/301). The power-amplified AF signals are passed through the AF mute SW (RL261), then applied to the internal speaker (SP1) via the external SP jack (J751), or an external speaker on the MAIN UNIT. When the headphones are connected to the headphones jack (J2) on the FRONT UNIT, the power-amplified AF signals from the AF power AMP (IC281) are applied to the connected headphones. <TO THE AUDIO STORAGE> When recording received audio, recovered AF signals from the buffer (IC1571) are also send to the audio storage (IC203) on the LOGIC UNIT to be recorded. <OUTPUT FROM ACC PORT> The recovered AF signals from the buffer (IC1571) are amplified by AF AMPs (IC241), the amplified AF signals are applied to the VCA (IC231) to be adjusted its signal level. The level-adjusted AF signals are output from [ACC1] socket. SCOPE UNIT The 1st RX/TX IF signal from the buffer (Q1352) on the RF UNIT are passed through the scope IF SW (IC31), scope ATT, LPF and BPF (dual tuned), and amplified by scope AMP (Q2) then applied to the 2nd scope mixer (D101). The 1st IF signal is converted into the 45 MHz 2nd scope IF signal (S2IF), and filtered to remove unwanted signals, then amplified by the 2nd scope IF AMPs (Q201 and Q202). The amplified 2nd scope IF signal is applied to the 3rd scope mixer (D4) to be converted into the 200 kHz 3rd scope IF signal. The converted signal is amplified by the 3rd scope IF AMP (IC401), filtered by the active LPF (IC403), level-limited by the saturation AMP (IC404). The level-limited signal is applied to the ADC (IC501) which samples the 200 kHz 3rd scope IF signal (0–2.5 V) into digital signal, then applied to the DSP (IC601) as the serial data. The DSP processes input data, then output to the CPU to display the frequency and relative signal strength of RX signals on the spectrum screen. Downloaded from www.Manualslib.com manuals search engine

3 - 3 3-2 TRANSMITTER CIRCUITS MAIN UNIT The MAIN UNIT contains transmit circuits; from MIC AMP to modulator cicuit. • TX AF CIRCUITS The audio signals from the microphone (MIC signals) are amplified by MIC AMP (IC171) and level-adjusted by VCA (IC171). The level-adjusted MIC signals are passed through the MIC mute SW (IC201) and MIC line selector (IC211) which selects the MIC line; MIC signals from the microphone jack on the FRONT UNIT, or from [ACC1] socket on the MAIN UNIT. The MIC signals are then applied to the limiter AMP (IC221) which limits the amplitude of MIC signals. The amplitude- limited MIC signals are applied to the ADC (IC1251) via the unbalance-balance convert circuit (IC1311, 1321, 1331), to be converted into the 24-bit serial data. The serial data is applied to the DSP (IC1001) and processed as digital audio signals. The processed digital audio signals are then applied to the Digital to Analog Converter (DAC; IC1501) to be converted into the analog audio signals; as the 36 kHz 1st TX IF signal. The 1st TX IF signal is entered to the RF UNIT. RF UNIT RF UNIT contains transmit circuits; TX mixers and AMPs. The 36 kHz 1st TX IF signal from the MAIN UNIT is applied to the 1st TX mixer (IC503) to be mixed with the 491 kHz 3rd LO signal from the PLL UNIT, to be converted into the 455 kHz 2nd TX IF signal. The converted 2nd TX IF is amplified by the 2nd IF AMP (Q501), filtered by 2nd TX IF filter (FI1501 for BW=20 kHz or FI1502 for BW=4 kHz). The filtered 2nd TX signal is amplified by 2nd IF AMP (Q504), and applied to the 2nd TX mixer (D505) to be mixed with the 64 MHz 2nd LO signal from the PLL UNIT, to be converted into the 64.455 MHz 3rd TX IF signal. The converted 3rd TX IF signal is passed through the BPF (FI503), amplified by 3rd IF AMP (Q506), and filtered by the LPF. The filtered 3rd TX IF signal is applied to the 3rd TX mixer (D506) to be mixed with the 3rd LO signal from the PLL UNIT, to be converted into the 4th TX IF signal (=TX signal). The converted TX signal is filtered by the LPF, amplified by RF AMP (Q508), passed through one of BPFs, then applied to the YGR AMP (Q801). The amplified TX signal is entered to the PA200W BOARD. PA200W BOARD • TX AMPLIFIERS The TX signal from the RF UNIT is amplified by the RF AMP (Q101), Pre-drive (Q201), drive (Q301) and power (Q401A, B) amplifiers in sequence, to obtain TX output power. The power-amplified TX signal is entered to the FILTER UNIT. FILTER UNIT • TX FILTERS The power-amplified TX signal from the PA200W BOARD is passed through one of BPFs (according to the TX frequency) to remove unwanted signals including harmonic components. The filtered TX signal is then entered to the CTRL BOARD. CTRL BOARD The CTRL BOARD mainly contains circuits for parameter detection of TX signal; Forward Wave, Reflected wave, Reactance, Resistance, antenna current and voltage. TX signal from the FILTER UNIT is passed through several detection circuits in sequence, then applied to the antenna [ANT1]–[ANT4]. • FOR (Forward Wave) voltage detection circuit A portion of TX signal is rectified by current trans (L101) and diode (D102), and the produced DC voltage is composed by C103, C106 and C116 to detect FOR voltage (Forward wave components). The detected voltage is amplified by IC101 and applied to the A/D port of CPU (IC1). • REF (Reflected Wave) voltage detection circuit A portion of TX signal is rectified by current trans (L101) and diode (D101), and the produced DC voltage is composed by C102, C105, C115, C120 and C121 to detect REF voltage (Reflected wave components). The detected voltage is amplified by IC101 and applied to the A/D port of CPU (IC1). • Reactance components detection circuit A portion of TX signal which is detected by current trans (L151) and TX signal which is divided by C153 and C158 are amplified by C-MOS IC. This AMP, as the first stage, employs a C-MOS type AMP to detect the low TX signal. The inverter AMP requires input level lower than others need, and provides high speed operation for stable high frequency operation with low TX signal. The amplified signal is adjusted its waveform, then applied to the IC155 and IC156 for phase comparison. The output signal is rectified by D153 and D154, composed and amplified by IC201, then applied to the A/D port of the CPU (IC1). • Resistance components detection A portion of TX signal which is detected by current trans (L201) and TX signal which is divided by C202, C205 and C206 are adjusted so that two of these are the same on the voltage. And two of these are rectified composed each other to detect the resistance components. When the detected voltage is increased, Q201 is activated to amplify the signal for high detection sensitivity. Downloaded from www.Manualslib.com manuals search engine

3 - 4 3-3 FREQUENCY SYNTHESIZER CIRCUITS PLL UNIT PLL UNIT provides LO signals; 1st LO for TX/RX IF circuits, 2nd RX LO (64.491 MHz), 2nd TX LO (64 MHz), 3rd TX LO (491 kHz), marker frequency (100 kHz), reference frequency for the SCOPE UNIT (40 MHz) and clock signal for the DSP UNIT (12.888 MHz). These LO signals are generated by the reference signal from the OSC UNIT as reference. This transeiver employs the Direct Digital Synthesizer (DDS) which digitally creates arbitrary waveforms and frequencies from a fixed source frequency, to provide extremely high resolution and stability frequency and pure waveform. • Reference frequency signal The 10 MHz reference frequency signal generated on the OSC UNIT is applied to the 4th harmonic extractor (Q702, L702, 703) via buffer (Q30) to produce the 40 MHz reference signal. • 1st LO signals The 40 MHz reference signal from the harmonic extractor is amplified by Q101, and applied to the DDS (IC101) as the clock signal. The DDS generates the 10.4122038 –10.4963312 MHz sine waves, and these are passed through the ceramic filter (FI101; Fc=10.7 MHz) to adjust the waveform, then applied to the PLL IC (IC201) via buffer (Q151). The PLL IC (IC201) controls the oscillating frequency of 6 VCOs (VCO1 to VCO6) using the reference signal generated by the DDS as reference frequency. The output signals of each VCOs (1st LO signals) are buffer-amplified by Q301, passed through the HPF and LPF, then amplified by the 1st LO AMPs (Q302 and Q351). The amplified 1st LO signals are buffer-amplified by Q352, passed through the LPF, HPF and ATT, then output to the RF UNIT as 1st LO signals (64.485–124.455 MHz). • 2nd LO signals The 40 MHz reference signal from the harmonic extractor is amplified by IC503, and applied to the DDS (IC501) as the clock signal. The DDS generates the reference frequency which controls the oscillating frequency of 64 MHz VCO (Q541). The output signal of 64 MHz VCO (Q541) is buffer-amplified by Q561, and applied to the hybrid divider. The hybrid divider divides the VCO output into two; 2nd TX LO and 2nd RX LO. <2nd TX LO signal> The VCO output signal from the hybrid divider is passed through the ATT, and applied to the 2nd LO AMP (Q591). The amplified VCO output signal is passed through the BPF, then entered to the RF UNIT as the 2nd TX LO signal. <2nd RX LO signal> The VCO output signal from the hybrid divider is passed through the ATT, and applied to the 2nd LO AMP (Q801). The amplified VCO output signal is passed through the ATT and, applied to the 2nd LO mixer (D821) and mixed with the 491 kHz 3rd TX LO signal from the 3rd TX LO oscillator (IC651), to convert into the 64.491 MHz 2nd RX LO signal. The converted 2nd RX LO signal is passed through the ATT and BPF, and applied to the 2nd LO AMP (Q831). The amplified signal is entered to the RF UNIT as the 2nd RX LO signal. • 3rd TX LO signal The 40 MHz reference signal from the harmonic extractor is amplified by IC652, and applied to the DDS (IC565) as the clock signal. Using the clock signal, the DDS directly generates the 491 kHz 3rd TX LO signal. The output signal of DDS is passed through the LPF and HPF, and applied to the buffer AMP (Q680). The buffer- amplified 2rd TX LO signal is entered to the RF UNIT via ATT. • DSP system clock The 40 MHz reference signal from the harmonic extractor is amplified by IC1651, and applied to the DDS (IC1652) as the clock signal. Using the clock signal, the DDS directly generates 12.288 MHz system clock signal. The system clock signal is passed through the LPF and HPF, and applied to the buffer (Q1680). The buffer-amplified system clock signal is entered to the MAIN UNIT via ATT. • Scope clock The 40 MHz reference signal from the harmonic extractor is amplified by Q1601, and entered to the SCOPE UNIT. VCO Oscillator component Oscillating frequency VCO1 Q220 64.485–72.454999 MHz VCO2 Q230 72.455–79.454999 MHz VCO3 Q240 79.455–86.454999 MHz VCO4 Q250 86.455–94.454999 MHz VCO5 Q260 94.455–109.454999 MHz VCO6 Q270 109.455–124.455 MHz Downloaded from www.Manualslib.com manuals search engine

ICOM IC-7700 Service Repair Manual

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