IC-R75_serv_1999.pdf

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1、SERVICE MANUAL COMMUNICATIONS RECEIVER This service manual describes the latest service information for the IC-R75 at the time of publication. NEVER connect the receiver to an AC outlet or to a DC power supply that uses more than 16 V. Such a connection could cause a fire hazard and/or electric. DO

2、NOT expose the receiver to rain, snow or any liquids. DO NOT reverse the polarities of the power supply when connecting the receiver. DO NOT apply an RF signal of more than 20 dBm (100mW) to the antenna connector. This could damage the receivers front end. Be sure to include the following four point

3、s 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 0910051123 PCBB-5274CIC-R75PLL UNIT1 pieces 8810005770 ScrewBih M3x8 ZKIC-R75Chassis10 pieces Addresses are provided on the inside back cover for

4、your convenience. 1. Make sure a problem is internal before disassembling the receiver. 2. DO NOT open the receiver until the receiver is discon- nected 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 pa

5、rts. An insulat- ed turning tool MUST be used for all adjustments. 5. DO NOT keep power ON for a long time when the receiv- er is defective. 6. READ the instructions of test equipment thoroughly before connecting equipment to the receiver. To upgrade quality, all electrical or mechanical parts and i

6、nternal circuits are subject to change without notice or obligation. VERSION U.S.A. Europe U.K. S.E.Asia Other SYMBOL USA EUR UK SEA OTH INTRODUCTIONDANGER ORDERING PARTSREPAIR NOTES TABLE OF CONTENTS SECTION1SPECIFICATIONS SECTION2INSIDE VIEWS SECTION3CIRCUIT DESCRIPTION 3-1RECEIVER CIRCUITS . . .

7、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1 3-2PLL CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4 3-3LOGIC CIRCUITS . . . . . . . . . . . . . . . . . . . . .

8、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5 3-4POWER SUPPLY CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-6 3-5 PORT ALLOCATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9、. . . . . . . . . . . .3-7 SECTION4ADJUSTMENT PROCEDURES 4-1PREPARATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1 4-2PLL ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10、 . . . . . . . . .4-2 4-3RECEIVER ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4 4-4SET MODE ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7 SECTION5PARTS LIST SECTION6M

11、ECHANICAL PARTS AND DISASSEMBLY SECTION7SEMI-CONDUCTOR INFORMATION SECTION8BOARD LAYOUTS 8-1PHONE AND VR BOARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1 8-2DISPLAY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12、. . . . . . . . . . . . . . . . . . . . . .8-3 8-3LOGIC BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5 8-4PLL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13、 . . . . . . . . .8-6 8-5MAIN UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-7 SECTION9BLOCK DIAGRAM SECTION10VOLTAGE DIAGRAM 10-1FRONT UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14、. . . . . . . . . . . . . . . . . . . . .10-1 10-2PLL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-2 10-3MAIN UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15、 . . . . . . . . . . . .10-3 1 - 1 MGENERAL Frequency range: * 1 Specifications guaranteed for 0.1 29.99 MHz and 50 54 MHz * 2 Specifications guaranteed for 0.1 29.99 MHz Mode: SSB (LSB, USB), AM, FM, CW, RTTY, S-AM Receive system: Triple-conversion superheterodyne Intermediate frequencies: May diff

16、er according to selected IF filter. Sensitivity: 0.1 MHz 1.799 MHz (Preamplifiers are OFF) SSB, CW, RTTYless than 2.0 V for 10 dB S/N AM, S-AMless than 13.0 V for 10 dB S/N 1.8 MHz 27.99 MHz (The preamplifier 1 is ON) SSB, CW, RTTYless than 0.16 V for 10 dB S/N (typical) AM, S-AMless than 2.0 V for

17、10 dB S/N 28 MHz 29.99 MHz (The preamplifier 1 is ON) SSB, CW, RTTYless than 0.16 V for 10 dB S/N (typical) AM, S-AMless than 2.0 V for 10 dB S/N FMless than 0.5 V for 12 dB SINAD 50 MHz 54 MHz (The preamplifier 2 is ON) SSB, CW, RTTYless than 0.13 V for 10 dB S/N (typical) AM, S-AMless than 1.0 V f

18、or 10 dB S/N FMless than 0.25 V for 12 dB SINAD selectivity: SSB, CW, RTTYMore than 2.1 kHz/6 dB Less than 4.0 kHz/60 dB AM, S-AMMore than 6.0 kHz/6 dB less than 20.0 kHz/50 dB FMMore than 12.0 kHz/6 dB less than 30.0 kHz/40 dB Audio output power: More than 2.0 W at 10 % distortion with an 8 load An

19、tenna impedance: 50 or 450 Squelch sensitivity (threshold): *Preamplifiers are OFF; * 1Preamplifier 1 is ON; *2Preamplifier 2 is ON Current drain (13.8 V DC): Less than 1.3 A (Standby), Less than 1.5 A (Max. audio out) Spurious and image rejection : More than 70 dB (0.1 1.799 MHz SSB, AM, S-AM are m

20、ore than 60 dB) Dimensions : 241(W)94(H)229(D) mm; 912(W)31116(H)9132(D) inch (projection not included) Weight (approximate): 3.0 kg; 6 lb 10 oz (AC adaptor “AD55/A/V” is not included) Antenna connector: SO-239 (50 ), push connection terminal (450 ) CI-V connector: 2-connector 3.5 (d) mm (18)/8 PHON

21、ES connector: 3-conductor 6.35 (d) mm (18) External speaker connector: 2-conductor 3.5 (d) mm (18)/8 SECTION 1SPECIFICATIONS All stated specifications are subject to change without notice or obligation. 1st (MHz) 2nd (MHz) 3rd (MHz) SSB 69.0115 9.0115 0.4550 CW 69.0106 9.0106 0.4559 RTTY 69.0105 9.0

22、105 0.4560 AM, S-AM 69.0100 9.0100 0.4500 FM 69.0115 9.0115 0.4500 Frequency (MHz) 0.1 1.799 1.8 27.99 28 29.99 50 54 SSB less than 71 V* less than 5.6 V* 1 less than 5.6 V* 2 FM less than 0.32 V* 1 less than 0.32 V* 2 Frequency coverage 30 kHz 60 MHz* 1 30 kHz 30 MHz* 2 Version USA, EUR, UK, OTH SE

23、A 2 - 1 SECTION 2INSIDE VIEWS 2nd IF filter (FI761: FL-272) 3rd LO circuit 3rd mixer circuit (IC811) BFO circuit 2nd IF circuit PLL IC (IC21) Noise blaker circuit VCO circuit BFO mixer circuit (IC1101) Bandpass filter Fuse (3A) MAIN UNITPLL UNIT Back up battery (BT 1521) 3rd IF filter (FI851) 2nd mi

24、xer circuit 1st IF filter (FI701) 1st mixer circuit SECTION 3CIRCUIT DESCRIPTION 3 - 1 3-1 RECEIVER CIRCUITS 3-1-1 RF SWITCHING CIRCUIT (MAIN UNIT) The IC-R75 has two antenna connectors. RF signals enter either the 50 ANT. or 450 ANT. connector. RF signals from the 50 ANT. connector are applied to t

25、he antenna switching circuit (RL121), and then pass through the low-pass filter (L131, L132, C131C136). RF signals from the 450 ANT. connector are passed through the L101 to exchange the impeadance value, and are then applied to the antenna switching circuit (RL121). The signals are applied to the l

26、ow-pass filter (L131, L132, C131C136). Each RF signals from the 50 ANT. connector or 450 ANT. connector are chosen by the antenna switching circuit (RL121). 3-1-2 RF FILTER CIRCUIT (MAIN UNIT) The filtered signals are applied to the RX attenuator switch- ing circuit (RL141). Either the signals bypas

27、s or pass through the attenuator circuit. The signals are attenuated at 20 dB when passing through the attenuators. The attenuator sys- tem excludes non-linear components between an antenna connector and an attenuator to prevent strong signals from causing distortion. The signals are then applied to

28、 the RF fil- ters. The MAIN UNIT has 8 RF bandpass fileters for signals above 2.0 MHz and 2 low-pass filters for signals below 2.0 MHz. (1) Below 1.6 MHz The signals are applied to the low-pass filter consisting of C170C175, L171L173 via the limitter circuit (D141, D142). A diode is removed at the e

29、ntrance of the low-pass filter. This device prevents the diode from causing distortion when receiving very strong signals. A switching diode (D172) is turned on when the “B0” line is “HIGH”. (2) Above 1.6 MHz The signals are applied to the high-pass filter consisting of C161C163, L161L164. This filt

30、er suppresses strong sig- nals below 1.6 MHz such as broadcasting stations. The filtered signal between 1.6 MHz and 2.0 MHz are applied to the low-pass filter (C182C187, L182, L183) via the switching diode (D181). The switching diodes (D181, D182) are turned ON when the “B1” line is “HIGH”. The filt

31、ered signals above 2.0 MHz are applied to one of 8 bandpass filters depending on the receive frequencies. After passing through a bandpass or low-pass filter, the sig- nals are applied to the pre-amplifier circuit (Q381, Q382, IC391). (3) FILTER SWITCHING CIRCUIT The RF bandpass filter corresponds t

32、o the BPF switching voltage (B0B9) based on the CPU via the shifit registor (IC551, IC552) and driver (IC561, IC562). The switching volt- age of the BPF exit ot improve multi-signal and strong signal characteristics. RF bandpass and preamplifier circuit ANT1 (50 ) ANT2 (450 ) ATT (20 dB) HPF LPF 0.5

33、 1.6 MHz 1.6 54 MHz ATT (10 dB) LPF B0 1.6 2.0 MHz B1 BPF 2.0 4.0 MHz B2 BPF 50 60 MHz B9 PRE AMP Q381, Q382 PRE AMP IC391 LPF 60 MHz to 1st mixer (Q441, Q442) preamplifier circuit 3 - 2 3-1-3 PRE-AMPLIFIER CIRCUIT (MAIN UNIT) The pre-amplifier circuit uses low noise junction FETs (Q381, Q382) or wi

34、deband amplifier (IC391) to provide gain over a wide frequency range. When the P.AMP switch is turned “PREAMP 1”, the signals from the RF filter are amplified by the junction FETs pre- amplifier circuit (Q381, Q382). When the P.AMP switch is turned “PREAMP 2”, the signals from the RF filter are ampl

35、ified by the wideband pre-amplifi- er circuit (IC391). When the P.AMP switch is turned “PREAMP OFF”, the sig- nals from the RF filter bypass the pre-amplifiers through D371 and D372. The amplified or bypassed signals are applied to the 1st mixer circuit (Q441, Q442) via the low-pass filter (L431, L4

36、32 and C431CC436). The low-pass filter attenuates at 50 MHz to suppress image frequency. 3-1-4 1ST MIXER AND IF CIRCUITS (MAIN UNIT) The filtered signals are mixed with a 69.0415129.0115 MHz 1st LO signal to produce a 69.01 MHz 1st IF signal at the 1st mixer circuit (Q441, Q442). The 1st mixer circu

37、it employs a balanced mixer using low- noise junction FETs (Q441, Q442) to expand the dynamic range. The 69.0415129.0115 MHz 1st LO signal is applied to an LO amplifier (Q411) from the PLL unit via J411, and then passes through the low-pass filter (L421, L422, C422C425). The filtered signal is appli

38、ed to the 1st mixer circuit. The 1st IF signal is applied to the crystal bandpass filter(FI- 461) to suppress out-of-band signals. The filtered signal is amplified at a 1st IF amplifier (Q471), and then applied to a 2nd mixer circuit (D491) 3-1-5 2ND MIXER AND IF CIRCUITS (MAIN UNIT) The 1st IF sign

39、al is mixed with a 60.0 MHz 2nd LO signal to produce 9 MHz 2nd IF signal at the 2nd mixer (D491, C492, L491, L492). The 60.0 MHz 2nd LO signal is applied to the 2nd mixer from the PLL unit via J491. The 9 MHz 2nd IF signal is applied to the crystal bandpass filter (FI701) to suppress unwanted signal

40、s. The filtered signal enters the noise blanker gate (D711D714). The signal is applied to L712 to obtain clear reception and is then amplified at the 2nd IF amplifier (Q721). The signal passes through a loose resonator circuit (C726, L721) and then is applied to one of the two crystal bandpass filte

41、rs. MODE LSB, USB, FM CW RTTY AM, S-AM FREQUENCY 69.0115 MHz 69.0106 MHz 69.0105 MHz 69.0100 MHz 1ST IF FREQUENCY IF circuit Received signals 1st LO signal 59.0155129.0115 MHz BPF IF AMP Q441, Q442 1st mixer Q471 2nd LO signal 60 MHz D491 2nd mixer NB GATE Noise Blanker IF AMP Q7213 kHz BPF BPF Opti

42、on Buffer Q801 Option BPF BPF 3 kHz BPF 6 kHz BPF 15 kHz IF AMP Q891 IF AMP Q911, Q912 IC811 3rd mixer 3rd LO signal 9.4665 MHz IC1101 BFO circuit BFO signal 455 kHz IF AMP Q1001 FM detector de- emphasis Buffer AM detector AGC detector AGC AMP IC1001, X1001 IC1211D IC2001, Q2021, X2021 Q1031 D1061Q1

43、063 AGC signal AF selector IC1201 LPF PWR AMP AF signal MODE LSB, USB, FM CW RTTY AM, S-AM FREQUENCY 9.0115 MHz 9.0106 MHz 9.0105 MHz 9.0100 MHz 2ND IF FREQUENCY 3 - 3 When the FIL switch is turned “2F3K”, the filter is selected FI761 which covering the 2.4 kHz bandwith. When the FIL switch is turne

44、d “2FOP”, the filter is selected an optional filter. When the FIL switch is turned “2FTH”, the signal from the 2nd IF amplifier bypass the crystal bandpass filters through D771 and D773. The filtered or bypassed signal is amplified at the buffer amplifier (Q801) and applied to the 3rd mixer circuit

45、(IC811). 3-1-6 NOISE BLANKER CIRCUITS (MAIN UNIT) The IC-R75 uses a trigger noise blanker circuit which removes pulse-type noise signals at the noise blanker gate (D711D714). The 2nd IF signal passes through the crystal bandpass filter (FI701) to suppress unwanted signals. A portion of the output si

46、gnal is applied to a noise amplifier circuit (IC731, Q731, Q733) and detected at a noise detector circuit (D731). The detected voltage is applied to a noise blanker gate control cir- cuit (Q735Q737, D732). The threshold level of the noise blanker gate control circuit (Q735Q737, D732) is set at 1.0 V

47、 on SSB mode (In case of AM mode, is set at 1.6 V). When the detected voltage exceeds the threshold level, Q737 outputs a blanking signal to activate the noise blanker gate (D711D714). A portion of the detected voltage is applied to the noise blanker AGC circuit (Q732, Q734). The noise components ar

48、e fed back to the noise amplifier (IC731). The time constant of the noise blanker AGC circuit is determined by R737, R744 and C739. This AGC circuit does not operate to detect pulse-type noise. When the operating frequency or mode is changed, the “UNLC” signal is applied to the noise blanker gate co

49、ntrol cir- cuit (D732). The noise blanker gate prevents PLL click noise. 3-1-7 3RD MIXER AND IF CIRCUITS (MAIN UNIT) The 2nd IF signal is mixed with a 9.4665 MHz 3rd LO signal to produce a 450456 kHz 3rd IF signal at the 3rd mixer (IC811). The 9.4665 MHz 3rd LO signal is applied to the 3rd mixer IC (IC811, pin 10) from the PLL unit via J811. The 450456 kHz 3rd IF signal is applied either to one of the 3 ceramic band- pass filters (FI851, FI861, FI871) or to an optional crystal bandpass filter to suppress unwanted sign