Icom Detailed Inside Views and Components of IC-T90A Marine Radio

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SECTION 2 INSIDE VIEWS

• LOGIC UNIT

Top view

RESET IC

(IC142: S-80928CNMC)

EEPROM

(IC2: HN58X24128FPI, Q2: UN9115)

• LOGIC UNIT

Bottom view

Crystal oscillator for CPU clock

(X1: CR-687, 6.7584 MHz, Q40: UN9215)

CPU

(IC1: M30220MA-114RP)

Microphone mute (Q310: XP6501)

Microphone amplifier (Q311: XP5601, Q312: XP6501)

AF regulator (Q201: 2SB1201, Q202: XP1501)

+3 regulator (Q8: 2SB1132, Q9: XP1501)

+3C regulator (Q142: XP1501, Q145: 2SB1132, D143: MA2S111)

CPU3 regulator (IC141: NJM2370U32)

440 MHz band modulation switch (Q304: 2SJ364)

145 MHz band modulation switch (Q305: 2SJ364)

50 MHz band modulation switch (Q342: 2SJ364)

2 - 1

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Contents IC-t90a Repair Notes IntroductionOrdering Parts Sample OrderTable of Contents Specifications GeneralTransmitter WFM ReceiverFrequency MHz WFMTop view Inside ViewsLogic Unit Bottom viewAF Unit RF UnitTop view Bottom view Disassembly Instructions Removing the rear panel Removing the AF unitCircuit Description Receiver Circuits4 1ST Mixer and 1ST if Circuits RF, AF and VCO Units 5 2ND if and Demodulator Circuits AF UnitRF Circuit AF Amplifier Circuit AF Unit Squelch Circuitaf and Logic Units2ND if and Demodulator Circuit Transmitter Circuits General PLL CircuitsAPC Circuit RF Unit APC CircuitVCO Divider Circuit VCO and RF Units PLL CircuitPort Allocations Power Supply Circuits2 R3V Switch IC AF Unit IC51 Voltage LineCPU Logic Unit IC1 LCD CtselDtcs SEG35Operation on the Output Power Adjustment Adjustment ProceduresOperation on the Adjustment Mode PreparationConnection JIGAD-92SMA VCO Trimmer AdjustmentPLL Lock VoltageL16 L456 VCO UnitRF Unit L19Dial Adjustment Mode AdjustmentsReference FrequencyAdjustment Mode Adjustments PH ch 53.900 MHz Transmitting 8V 145 MHz Displayed frequency Connect an amme 45 a R365 Logic UnitR325 R326Ctcss Detector CoilTracking IC151, pin 12 SD line AF UnitCP0 L151Displayed frequency Connect a DC volt Maximum voltage Adjustment Adjustment Condition Operation MeterSection Parts List Order DescriptionCoil Eljre 3N9Z-F Ceramic ECJ0EB1H681K Connector AXK6S30445P Ceramic ECJ0EC1H060C Encoder Trimmer Tantalum ECST1EY474R Ceramic ECJ0EC1H2R5B Mechanical Parts and Disassembly AccessoriesChassis Parts Chassis Parts Logic UnitRF Unit AF Unit VCO UnitDiodes SEMI-CONDUCTOR InformationTransistors and Fets NameMC1 Microphone Board LayoutsTOP View DUPSP1 Logic unitBottom View SQL PTTRF Unit RF unit AF Unit VCO UnitEXT.SP EXT.MICREMOTO S253S252 Block Diagram Logic UnitChassis Loop LPF HPF Drive BPF ANT FIL AMPVoltage Diagram 11 1 Logic UnitIC5 11 2 RF Unit 2SK347611 3 AF Unit BU4094BCFVURL 32, Kamiminami, Hirano-ku, Osaka 547-0003, Japan