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• SERVICE MANUAL MULTIBAND FM TRANSCEIVER. • SYMBOL U.S.A. USA-1 IC-T81A Australia S.E.Asia Europe IC-T81E U.K. Italy To upgrade quality, 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.
• TABLE OF CONTENTS SECTION SPECIFICATIONS SECTION INSIDE VIEWS SECTION DISASSEMBLY INSTRUCTIONS SECTION CIRCUIT DESCRIPTION RECEIVER CIRCUITS..4-1 TRANSMITTER CIRCUITS. • SECTION 1 SPECIFICATIONS GENERAL • Frequency range Version 145 MHz 440 MHz 1200 MHz 91.5 MHz (RX only) 50 MHz TX: 144 – 148 TX: 430 – 450 U.S.A. 1240 – 1300 76 – 107.995 50 – 53.995 RX: 118 – 173.995 RX: 400 –. • RECEIVER • Receiver system: Double-conversion superheterodyne • Intermediate frequency: 1st 69.45 MHz (13.35 MHz: WFM) 2nd 450 kHz • Sensitivity* (except spurious points; typical values) Band 50 MHz 0.56 µV – 0.18 µV 144 MHz 0.18 µV – –. • SECTION 2 INSIDE VIEWS • LOGIC UNIT BOTTOM VIEW Crystal filter (X1: CR-639 5.039MH) (IC1: M38267M8LGP) AF mute switch (Q361: 2SJ364) AF volume (IC202: M5222FP) AF power amplifier IF IC (IC201: TA7368F) (IC701: TA31136FN) • RF UNIT BOTTOM VIEW TOP VIEW Power amplifier (Q922: 2SK3075) Drive amplifier.
May 17, 2010 RE: Icom 731 versus 735 « Reply #3 on: May 17, 2010, 05:14:05 PM » Interesting, never heard of it, but looking at the picture it looks like a spittin image of my IC-735 - no way to tell what changed unless you search for more data but visually it's identical.
• SECTION 3 DISASSEMBLY INSTRUCTIONS • REMOVING THE CHASSIS PANEL • REMOVING THE SHIELD PLATE 1 Remove 1 knob A, and unscrew 1 nut B. 1 Unsolder 10 points, F, to separate the shield plate and 2 Unscrew 2 screws C. • SECTION 4 CIRCUIT DESCRIPTION 4-1 RECEIVER CIRCUITS Thus, transmit signals are blocked from entering the receiv- er circuits. The antenna switching circuit employs a 1/4 4-1-1 DUPLEXER CIRCUIT (RF UNIT) type diode switching system.
The passed signals are then The transceiver has a duplexer (low-pass and high-pass fil- applied to each RF amplifier circuit. • • RF signals WFM band • 50, 144, 440 and 1200 MHz band The WFM band signals are applied to the RF amplifier The applied RF signals are mixed with 1st LO signals at the (Q201) via the tunable band-pass filter (D202).
The ampli- 1st mixer (IC601) to produce a 69.45 MHz 1st IF signal. • 4-1-8 2ND IF AND DEMODULATOR CIRCUITS Even when the squelch is closed, the AF mute switch (Q361) opens at the moment of emitting beep tones. (RF AND LOGIC UNITS) The 2nd mixer circuit converts the 1st IF signal to the 2nd IF •. • The amplified signal is passed through the antenna switch- (3) 440 MHz band ing circuit (D101 and D102), low-pass filters and high-pass The signals from the limiter amplifier (RF unit; IC301) filters. The signal is applied to the antenna connector.
Changes the reactance of a diode (VCO unit. • The APC sensor (R911) detects driving current from the The applied signal is divided by serial data from the CPU (N- drive voltage at the YGR (Q138), drive (Q921) and power data) and phase-detected with the divided reference fre- (Q922) amplifiers. The detected current is converted into DC quency (5 kHz) at the phase detector section in the PLL IC. • 4-5 PORT ALLOCATIONS 4-5-2 I/O EXPANDER IC (RF UNIT; IC3) 4-5-1 I/O EXPANDER IC (RF UNIT; IC2) Port Port Description Description number name number name Outputs VHVCO3 regulator control Outputs 300 MHz band RX regulator signal. Control signal. Outputs VLVCO3 regulator control Outputs AM mode regulator control signal.
• 4-5-3 CPU (LOGIC UNIT; IC1) Port Port Description Description number name number name Input port for the over-voltage detec- CLONEIN Input port for the cloning signal. Tion from connected battery pack or Outputs T4 regulator control signal.
External power supply. High: While transmitting.
• SECTION 5 ADJUSTMENT PROCEDURES 5-1 PREPARATION ‘ ‘ REQUIRED TEST EQUIPMENT EQUIPMENT GRADE AND RANGE EQUIPMENT GRADE AND RANGE Output voltage: 13.5 V DC DC voltmeter Input impedance: 50 kΩ/V DC or better DC power supply Current capacity: 3 A or more Frequency range: 300–3000 Hz. • 5-2 PLL ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”.
ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST PLL LOCK • Displayed frequency: Connect 0.8 V – 1.8 V Verify VOLTAGE 51.000 MHz voltmeter •. • • RF UNIT BOTTOM VIEW 12LV PLL lock voltage check point (for 1200 MHz) PLL lock voltage check point (for 440 MHz) PLL lock voltage check point (for 50 MHz RX, WFM and 144 MHz) • RF UNIT TOP VIEW 6MLV PLL lock voltage check point (for 50 MHz TX) • 5-3 RECEIVER ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”. ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST 50 MHz • Displayed frequency: LOGIC Connect a multime- Maximum voltage [DIAL] SENSITIVITY 50.000 MHz ter to check point panel •. • • LOGIC UNIT TOP VIEW 50 MHz, WFM BAND, AIR BAND and 145 MHz Sensitivity check point 5 - 5. • RECEIVER ADJUSTMENT (Continued) The following adjustment must be performed on the normal mode after “SENSITIVITY ADJUSTMENT” in SECTION 5-3.
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• SERVICE MANUAL MULTIBAND FM TRANSCEIVER. • SYMBOL U.S.A. USA-1 IC-T81A Australia S.E.Asia Europe IC-T81E U.K. Italy To upgrade quality, 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.
• TABLE OF CONTENTS SECTION SPECIFICATIONS SECTION INSIDE VIEWS SECTION DISASSEMBLY INSTRUCTIONS SECTION CIRCUIT DESCRIPTION RECEIVER CIRCUITS..4-1 TRANSMITTER CIRCUITS. • SECTION 1 SPECIFICATIONS GENERAL • Frequency range Version 145 MHz 440 MHz 1200 MHz 91.5 MHz (RX only) 50 MHz TX: 144 – 148 TX: 430 – 450 U.S.A. 1240 – 1300 76 – 107.995 50 – 53.995 RX: 118 – 173.995 RX: 400 –. • RECEIVER • Receiver system: Double-conversion superheterodyne • Intermediate frequency: 1st 69.45 MHz (13.35 MHz: WFM) 2nd 450 kHz • Sensitivity* (except spurious points; typical values) Band 50 MHz 0.56 µV – 0.18 µV 144 MHz 0.18 µV – –. • SECTION 2 INSIDE VIEWS • LOGIC UNIT BOTTOM VIEW Crystal filter (X1: CR-639 5.039MH) (IC1: M38267M8LGP) AF mute switch (Q361: 2SJ364) AF volume (IC202: M5222FP) AF power amplifier IF IC (IC201: TA7368F) (IC701: TA31136FN) • RF UNIT BOTTOM VIEW TOP VIEW Power amplifier (Q922: 2SK3075) Drive amplifier.
May 17, 2010 RE: Icom 731 versus 735 « Reply #3 on: May 17, 2010, 05:14:05 PM » Interesting, never heard of it, but looking at the picture it looks like a spittin image of my IC-735 - no way to tell what changed unless you search for more data but visually it\'s identical.
• SECTION 3 DISASSEMBLY INSTRUCTIONS • REMOVING THE CHASSIS PANEL • REMOVING THE SHIELD PLATE 1 Remove 1 knob A, and unscrew 1 nut B. 1 Unsolder 10 points, F, to separate the shield plate and 2 Unscrew 2 screws C. • SECTION 4 CIRCUIT DESCRIPTION 4-1 RECEIVER CIRCUITS Thus, transmit signals are blocked from entering the receiv- er circuits. The antenna switching circuit employs a 1/4 4-1-1 DUPLEXER CIRCUIT (RF UNIT) type diode switching system.
The passed signals are then The transceiver has a duplexer (low-pass and high-pass fil- applied to each RF amplifier circuit. • • RF signals WFM band • 50, 144, 440 and 1200 MHz band The WFM band signals are applied to the RF amplifier The applied RF signals are mixed with 1st LO signals at the (Q201) via the tunable band-pass filter (D202).
The ampli- 1st mixer (IC601) to produce a 69.45 MHz 1st IF signal. • 4-1-8 2ND IF AND DEMODULATOR CIRCUITS Even when the squelch is closed, the AF mute switch (Q361) opens at the moment of emitting beep tones. (RF AND LOGIC UNITS) The 2nd mixer circuit converts the 1st IF signal to the 2nd IF •. • The amplified signal is passed through the antenna switch- (3) 440 MHz band ing circuit (D101 and D102), low-pass filters and high-pass The signals from the limiter amplifier (RF unit; IC301) filters. The signal is applied to the antenna connector.
Changes the reactance of a diode (VCO unit. • The APC sensor (R911) detects driving current from the The applied signal is divided by serial data from the CPU (N- drive voltage at the YGR (Q138), drive (Q921) and power data) and phase-detected with the divided reference fre- (Q922) amplifiers. The detected current is converted into DC quency (5 kHz) at the phase detector section in the PLL IC. • 4-5 PORT ALLOCATIONS 4-5-2 I/O EXPANDER IC (RF UNIT; IC3) 4-5-1 I/O EXPANDER IC (RF UNIT; IC2) Port Port Description Description number name number name Outputs VHVCO3 regulator control Outputs 300 MHz band RX regulator signal. Control signal. Outputs VLVCO3 regulator control Outputs AM mode regulator control signal.
• 4-5-3 CPU (LOGIC UNIT; IC1) Port Port Description Description number name number name Input port for the over-voltage detec- CLONEIN Input port for the cloning signal. Tion from connected battery pack or Outputs T4 regulator control signal.
External power supply. High: While transmitting.
• SECTION 5 ADJUSTMENT PROCEDURES 5-1 PREPARATION ‘ ‘ REQUIRED TEST EQUIPMENT EQUIPMENT GRADE AND RANGE EQUIPMENT GRADE AND RANGE Output voltage: 13.5 V DC DC voltmeter Input impedance: 50 kΩ/V DC or better DC power supply Current capacity: 3 A or more Frequency range: 300–3000 Hz. • 5-2 PLL ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”.
...'>Icom Ic 731 Service Manual(29.09.2018)
ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST PLL LOCK • Displayed frequency: Connect 0.8 V – 1.8 V Verify VOLTAGE 51.000 MHz voltmeter •. • • RF UNIT BOTTOM VIEW 12LV PLL lock voltage check point (for 1200 MHz) PLL lock voltage check point (for 440 MHz) PLL lock voltage check point (for 50 MHz RX, WFM and 144 MHz) • RF UNIT TOP VIEW 6MLV PLL lock voltage check point (for 50 MHz TX) • 5-3 RECEIVER ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”. ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST 50 MHz • Displayed frequency: LOGIC Connect a multime- Maximum voltage [DIAL] SENSITIVITY 50.000 MHz ter to check point panel •. • • LOGIC UNIT TOP VIEW 50 MHz, WFM BAND, AIR BAND and 145 MHz Sensitivity check point 5 - 5. • RECEIVER ADJUSTMENT (Continued) The following adjustment must be performed on the normal mode after “SENSITIVITY ADJUSTMENT” in SECTION 5-3.• SERVICE MANUAL MULTIBAND FM TRANSCEIVER. • SYMBOL U.S.A. USA-1 IC-T81A Australia S.E.Asia Europe IC-T81E U.K. Italy To upgrade quality, 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.
• TABLE OF CONTENTS SECTION SPECIFICATIONS SECTION INSIDE VIEWS SECTION DISASSEMBLY INSTRUCTIONS SECTION CIRCUIT DESCRIPTION RECEIVER CIRCUITS..4-1 TRANSMITTER CIRCUITS. • SECTION 1 SPECIFICATIONS GENERAL • Frequency range Version 145 MHz 440 MHz 1200 MHz 91.5 MHz (RX only) 50 MHz TX: 144 – 148 TX: 430 – 450 U.S.A. 1240 – 1300 76 – 107.995 50 – 53.995 RX: 118 – 173.995 RX: 400 –. • RECEIVER • Receiver system: Double-conversion superheterodyne • Intermediate frequency: 1st 69.45 MHz (13.35 MHz: WFM) 2nd 450 kHz • Sensitivity* (except spurious points; typical values) Band 50 MHz 0.56 µV – 0.18 µV 144 MHz 0.18 µV – –. • SECTION 2 INSIDE VIEWS • LOGIC UNIT BOTTOM VIEW Crystal filter (X1: CR-639 5.039MH) (IC1: M38267M8LGP) AF mute switch (Q361: 2SJ364) AF volume (IC202: M5222FP) AF power amplifier IF IC (IC201: TA7368F) (IC701: TA31136FN) • RF UNIT BOTTOM VIEW TOP VIEW Power amplifier (Q922: 2SK3075) Drive amplifier.
May 17, 2010 RE: Icom 731 versus 735 « Reply #3 on: May 17, 2010, 05:14:05 PM » Interesting, never heard of it, but looking at the picture it looks like a spittin image of my IC-735 - no way to tell what changed unless you search for more data but visually it\'s identical.
• SECTION 3 DISASSEMBLY INSTRUCTIONS • REMOVING THE CHASSIS PANEL • REMOVING THE SHIELD PLATE 1 Remove 1 knob A, and unscrew 1 nut B. 1 Unsolder 10 points, F, to separate the shield plate and 2 Unscrew 2 screws C. • SECTION 4 CIRCUIT DESCRIPTION 4-1 RECEIVER CIRCUITS Thus, transmit signals are blocked from entering the receiv- er circuits. The antenna switching circuit employs a 1/4 4-1-1 DUPLEXER CIRCUIT (RF UNIT) type diode switching system.
The passed signals are then The transceiver has a duplexer (low-pass and high-pass fil- applied to each RF amplifier circuit. • • RF signals WFM band • 50, 144, 440 and 1200 MHz band The WFM band signals are applied to the RF amplifier The applied RF signals are mixed with 1st LO signals at the (Q201) via the tunable band-pass filter (D202).
The ampli- 1st mixer (IC601) to produce a 69.45 MHz 1st IF signal. • 4-1-8 2ND IF AND DEMODULATOR CIRCUITS Even when the squelch is closed, the AF mute switch (Q361) opens at the moment of emitting beep tones. (RF AND LOGIC UNITS) The 2nd mixer circuit converts the 1st IF signal to the 2nd IF •. • The amplified signal is passed through the antenna switch- (3) 440 MHz band ing circuit (D101 and D102), low-pass filters and high-pass The signals from the limiter amplifier (RF unit; IC301) filters. The signal is applied to the antenna connector.
Changes the reactance of a diode (VCO unit. • The APC sensor (R911) detects driving current from the The applied signal is divided by serial data from the CPU (N- drive voltage at the YGR (Q138), drive (Q921) and power data) and phase-detected with the divided reference fre- (Q922) amplifiers. The detected current is converted into DC quency (5 kHz) at the phase detector section in the PLL IC. • 4-5 PORT ALLOCATIONS 4-5-2 I/O EXPANDER IC (RF UNIT; IC3) 4-5-1 I/O EXPANDER IC (RF UNIT; IC2) Port Port Description Description number name number name Outputs VHVCO3 regulator control Outputs 300 MHz band RX regulator signal. Control signal. Outputs VLVCO3 regulator control Outputs AM mode regulator control signal.
• 4-5-3 CPU (LOGIC UNIT; IC1) Port Port Description Description number name number name Input port for the over-voltage detec- CLONEIN Input port for the cloning signal. Tion from connected battery pack or Outputs T4 regulator control signal.
External power supply. High: While transmitting.
• SECTION 5 ADJUSTMENT PROCEDURES 5-1 PREPARATION ‘ ‘ REQUIRED TEST EQUIPMENT EQUIPMENT GRADE AND RANGE EQUIPMENT GRADE AND RANGE Output voltage: 13.5 V DC DC voltmeter Input impedance: 50 kΩ/V DC or better DC power supply Current capacity: 3 A or more Frequency range: 300–3000 Hz. • 5-2 PLL ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”.
...'>Icom Ic 731 Service Manual(29.09.2018) ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST PLL LOCK • Displayed frequency: Connect 0.8 V – 1.8 V Verify VOLTAGE 51.000 MHz voltmeter •. • • RF UNIT BOTTOM VIEW 12LV PLL lock voltage check point (for 1200 MHz) PLL lock voltage check point (for 440 MHz) PLL lock voltage check point (for 50 MHz RX, WFM and 144 MHz) • RF UNIT TOP VIEW 6MLV PLL lock voltage check point (for 50 MHz TX) • 5-3 RECEIVER ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”. ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST 50 MHz • Displayed frequency: LOGIC Connect a multime- Maximum voltage [DIAL] SENSITIVITY 50.000 MHz ter to check point panel •. • • LOGIC UNIT TOP VIEW 50 MHz, WFM BAND, AIR BAND and 145 MHz Sensitivity check point 5 - 5. • RECEIVER ADJUSTMENT (Continued) The following adjustment must be performed on the normal mode after “SENSITIVITY ADJUSTMENT” in SECTION 5-3.