Icom Sm-20 Service Manual
Icom SM-20 desktop microphone Subject: Icom SM-20 desktop microphone Keywords: Icom SM-20 desktop microphone Created Date: 2/19/2004 9:14:10 AM.
. SERVICE MANUAL COMMUNICATIONS RECEIVER iC-r20. DO NOT keep power ON for a long time when the receiver is defective.
READ the instructions of test equipment thoroughly before connecting equipment to the receiver. Icom, Icom Inc. And are registered trademarks of Icom Incorporated (Japan) in the United States, the United Kingdom, Germany, France, Spain, Russia and/or other countries. TABLE OF CONTENTS SECTION SPECIFICATIONS SECTION INSIDE VIEWS SECTION DISASSEMBLY INSTRUCTIONS SECTION CIRCUIT DESCRIPTION RECEIVER CIRCUITS. 4 - 1 PLL CIRCUITS. SECTION 1 SPECIFICATIONS.
IC-R20 RECEIVER GENERAL. Receiver system: Triple super heterodyne and down convertor.
Frequency coverage. Intermediate frequency: 1st 266.7 and 429.1 MHz 2nd 19.65 MHz Receive coverage (MHz) Version 450 kHz EUR, UK,. BC-156. Input voltage: 8.0–16.0 V. Charging current: 0.96–1.44 A (Rapid charging). Usable temperature: 0˚C to +35˚C (+32˚F to +95˚F). Timer device: 192–288 minutes (Rapid charging) 12–18 minutes (Reserve charging).
Protect function FUNCTION BP-206 CONDITION BC-156 ACTION. SECTION 2 INSIDE VIEWS 2-1 RF UNIT. Top view B-UHF RF amplifier A/B-UHF (pre-amplifier (Q551: PA805T) (Q548: 2SC5006) Highpass filter circuit (C854, C856, C858) Lowpass filter circuit (L123—L125) A-UHF RF amplifier 1G RF amplifier (Q35: 2SC5006) (Q26: 2SC5624) 30—300 MHz RF amplifier (Q36: 2SC5006) 470—833 MHz RF amplifier. 2-2 LOGIC UNIT. Bottom view.
Top view AF amplifier regulator (Q7: XP1501 Q9: 2SB1132) AF amplifier (IC15: TA31056F Q8: 2SA1588) (DS12: M3-0243TIY) BFO circuit IC6: SN74AHC1GU04DBVR X2: CSBFB543K AF pre-amplifiers (Q12, Q16: 2SC4617) +3 regulators (Q10, Q15: 2SA1362) Reset IC A-BAND AF circuit (IC2: BD5228G). SECTION 3 DISASSEMBLY INSTRUCTIONS (1) REMOVING THE REAR PANEL (3) REMOVING THE REC UNIT q Unscrew 4 screws, A (2 × 115 mm, black). Q Unscrew 4 flat-head screws, H (2 × 4 mm, silver). W Unscrew 2 screws, B (2 × 8 mm, black). W Unsolder 1 point, I. SECTION 4 CIRCUIT DESCRIPTION 4-1 RECEIVER CIRCUITS. A-BAND CIRCUIT (1) MF (above 0.15 MHz, below 1.9 MHz) signals 4-1-1 BAND SWITCHING CIRCUIT (RF UNIT) RF signals (0.15–1.9 MHz) from an attenuator (D69) pass The RF signals from the antenna connector pass through through the low-pass filter (L123–L125 and C851–C853), the limiter (D68) and an attenuator.
(D69). (3) HF-H (above 15 MHz, below 30 MHz) signals (3) 800M (above 470 MHz, below 833 MHz) signals RF signals (15–30 MHz) from an attenuator (D69) pass RF signals (470–833 MHz) from an attenuator (D69) pass through the low-pass filter (L123–L125 and C851–C853), through the high-pass filter (L126, L127 and C854–C858) band switch (D73) and bandpass filter (L81–L84 and and band switch (D11).
B-BAND CIRCUIT 4-1-6 3RD MIXER AND DEMODULATOR CIRCUITS The RF signals from the band switch (D32, D36, D143 and (RF UNIT) D147) are amplified at the RF amplifier (IC18, pins 1, 4), and The 3rd mixer circuit converts the 2nd IF signal to a 3rd IF are mixed with 1st LO signals at the 1st mixer circuit (IC15, signal. (3) AM MODE (1) FM MODE The 3rd IF signal is output from the FM IF IC (IC2, pin 3), The 3rd IF signal is output from the FM IF IC (IC17, pin 3), and passes through the mode switch (D109) and ceramic and passes through the mode switch (D134) and ceramic bandpass filter (FI2). While in WFM/AM modes, AF signals from the demodulator (3) AM MODE circuit (RF unit) bypass the AF filter via the AF filter bypass The 3rd IF signal is output from the FM IF IC (IC17, pin 3), switch (Q27), and are then amplified at the AF amplifier and passes through the mode switch (D134) and ceramic (Q22). (1) A-BAND CIRCUIT The A-AGC or B-AGC voltage is used for the the bias volt- A portion of the AF signals from the FM IF IC (RF unit; IC2, age of the IF and RF amplifiers. When receiving strong sig- pin 9) passes through the low-pass filter (LOGIC unit. 4-2 PLL CIRCUITS 4-2-2 REFERENCE OSCILLATOR CIRCUIT (RF UNIT) 4-2-1 PLL CIRCUIT The reference oscillator circuit (X1, Q556, D171) generates A PLL circuit provides stable oscillation of the 1st LO fre- a 19.2 MHz reference frequency which is stabilized within quencies.
A portion of the signal from the buffer amplifier (IC2) is A part of oscillated signal from the 2nd C-VCO circuit is amplified at the buffer amplifier (Q8) and is then fed back to applied to the PLL IC (IC1, pin 8) as the comparison signal, the PLL IC (IC3, pin 11) as the comparison signal. B-BAND CIRCUIT (2NDDVCO BOARD). B-BAND CIRCUIT The 2nd D-VCO circuit (Q1 and D1) generates 247.0500 The 19.2 MHz reference signal is amplified at the LO ampli- MHz and 286.3500 MHz. The oscillated signal is applied to fier (Q555), and is then applied to the FM IF IC (IC17, pin 2) the 2nd mixer (RF unit.
4-2-7 BFO CIRCUIT (LOGIC UNIT) The oscillated signal at the BFO VCO circuit (IC6, X2) is applied to the MAIN unit via the J5 (pin 35) as the BFO, and is then amplified at the BFO amplifier (RF unit; Q530). The amplified signal is mixed with 3rd IF signal to demodulate to AF signal on SSB/CW modes.
4-4 POWER SUPPLY CIRCUITS 4-4-3 RF UNIT VOLTAGE LINES 4-4-1 LOGIC UNIT VOLTAGE LINES Description Line Description Receive 3 V line from the LOGIC unit via the J1, Line pin 37. The voltage is supplied to the RF (IC19), The voltage is same as connected battery pack. AR3V IF (Q5) and LO (Q540) amplifiers, 1st (IC1) and The voltage is supplied to the charge controller.
Sm 20 2 Manual
(LOGIC unit; IC3)–Continued 4-5 PORT ALLOCATIONS 4-5-1 MAIN CPU PORT ALLOCATIONS Port Description number name (LOGIC UNIT; IC3) Outputs strobe signal to the D/A con- STR2 verter IC (IC22, pin 1). Port Description number name 49–52 KS3–KS1 Output key matrix signals. DATAC Outputs data and clock control signal. 4-5-4 D/A CONVERTER IC PORT ALLOCATIONS 4-5-2 SUB CPU PORT ALLOCATIONS (RF UNIT; IC14) (REC UNIT; IC2) Port Port Description Description number name number name RSTO Input port for the USB reset signal. Outputs VHF band selecting signal at AVHFC the A-BAND circuit. 4-6-3 CHARGING CONTROL CIRCUIT (MAIN UNIT AND TANSHI BOARD) 4-6-1 DC/DC CONVERTER CIRCUIT (MAIN UNIT).
CHARGING THE BATTERY WITH IC-R20 Input voltage (8–16 V) from the BC-123A/E pass through The “DET2” signal from the TANSHI board is applied to the reverse protection circuit (D6) via the J1. 0.1 V to 32 mV 3.5(d) mm ( 127 dBm to 17 dBm) 3-conductor 3.5(d) mm plug must be used.
To SP jack Power supply to DC 6 V / 1 A jack IC-R20 5 - 1. Connect an SSG to the antenna connector and set as. Set an SSG’s level to 10 dB S/N sensitivity (A). SHIFT Frequency: 14.0990 MHz. Measure the AF output level while the IC-R20 LSB-IFS Modulation: OFF outputs 1 kHz signal (B). RF UNIT BOTTOM VIEW. RF UNIT TOP VIEW L105 CP18 Center voltage adjustment (B-BAND) Reference frequency check point CP11 Center voltage check point (B-BAND) Center voltage adjustment (A-BAND) Center voltage check point (A-BAND).
BFO CHECK POINT (LOGIC UNIT TOP VIEW) BFO check point 5 - 3. SOFTWARE ADJUSTMENTS–Continued ADJUSTMENT ADJUSTMENT CONDITION OPERATION. Mode: FM. Push. LOCK key.
AFC. Connect an SSG to the antenna connector and set as Level: 1 mV. (–47 dBm) A-BAND) Frequency: 145.100 MHz Modulation: OFF. SOFTWARE ADJUSTMENTS–Continued ADJUSTMENT ADJUSTMENT CONDITION OPERATION S-METER. Mode: FM. Push 8 SET key. S-M.
Connect an SSG to the antenna connector and set as (1.81 MHz Level: 0.56 µV. (–112 dBm) FM mode) Frequency: 1.81 MHz Modulation: ±1 kHz Deviation. SOFTWARE ADJUSTMENTS–Continued ADJUSTMENT ADJUSTMENT CONDITION OPERATION S-METER. Mode: FM. Push 8 SET key. S-M.
Connect an SSG to the antenna connector and set as (1400.1 MHz Level: 0.56 µV. (–112 dBm) FM mode) Frequency: 1400.1 MHz Modulation: ±1 kHz Deviation. SOFTWARE ADJUSTMENTS–Continued ADJUSTMENT ADJUSTMENT CONDITION OPERATION S-METER. Mode: FM. Push 8 SET key. S-M. Connect an SSG to the antenna connector and set as (2510.1 MHz Level: 0.56 µV.
(–112 dBm) FM mode) Frequency: 2510.1 MHz Modulation: ±1 kHz Deviation. SECTION 6 PARTS LIST 6-1 IC-R20 1STAVCO BOARD ORDER 1STAVCO BOARD DESCRIPTION ORDER DESCRIPTION S.RESISTOR ERJ2GEJ 102 X (1 kΩ) S.RESISTOR ERJ2GEJ 102 X (1 kΩ) S.IC µPC2746TB-E3 S.RESISTOR ERJ2GEJ 102 X (1 kΩ) S.IC MB15T61ULPVA-G-ER S.RESISTOR.
1STAVCO BOARD 1STBVCO BOARD ORDER ORDER DESCRIPTION DESCRIPTION S.CERAMIC ECJ0EB1E102K S.RESISTOR ERJ2GEJ 822 X (8.2 kΩ) ERJ2GEJ 471 X (470 Ω) EUR, UK, USA, CAN B S.RESISTOR CONNECTOR IMSA-9230B-1-07Z064-T S.RESISTOR ERJ2GEJ 682 X (6.8 kΩ) ERJ2GEJ 121 X (120 Ω) CONNECTOR IMSA-9230B-1-08Z064-T.