Page 2 - NEVER; ORDERING PARTS; REPAIR NOTES
INTRODUCTION This service manual describes the latest service information for the IC-T90A MULTIBAND FM TRANSCEIVER at the time of publication. T90A U.S.A. General Canada S.E. Asia USA GEN CAN SEA To upgrade quality, all electrical or mechanical parts and inter-nal circuits are subject to change with...
Page 3 - TABLE OF CONTENTS
TABLE OF CONTENTS SECTION 1 SPECIFICATIONS SECTION 2 INSIDE VIEWS SECTION 3 DISASSEMBLY INSTRUCTIONS SECTION 4 CIRCUIT DESCRIPTION 4 - 1 RECEIVER CIRCUITS ................................................................................................... 4 - 1 4 - 2 TRANSMITTER CIRCUITS ...............
Page 4 - SECTION 1
1 - 1 M GENERAL • Frequency range : (Unit: MHz) * 1 Specifications guaranteed 144 – 148 MHz * 2 Specifications guaranteed 440 – 450 MHz * 3 Specifications guaranteed 430 – 440 MHz * 4 Except 824 – 849 MHz, 869 – 894 MHz [USA] only • Mode : FM, AM (RX only) and WFM (Rx only) • Number of memory channe...
Page 5 - RECEIVER
1 - 2 All stated specifications are subject to change without notice or obligation. M RECEIVER • Receiver system : Double-conversion superheterodyne • Intermediate frequency : 1st 13.350 MHz (FM/AM)13.350 MHz (WFM) 2nd 450 kHz • Sensitivity* 1 : (except spurious points; typical values) * 1 FM and WF...
Page 6 - • LOGIC UNIT
2 - 1 SECTION 2 INSIDE VIEWS EEPROM(IC2: HN58X24128FPI, Q2: UN9115) RESET IC(IC142: S-80928CNMC) Crystal oscillator for CPU clock(X1: CR-687, 6.7584 MHz, Q40: UN9215) CPU(IC1: M30220MA-114RP) AF regulator(Q201: 2SB1201, Q202: XP1501) +3 regulator(Q8: 2SB1132, Q9: XP1501) +3C regulator(Q142: XP1501, ...
Page 7 - • RF UNIT; • AF UNIT; • RF UNIT
2 - 2 50 MHz TX low-pass filter circuit 144 MHz TX high-pass filter circuit Pre-drive(Q54: 2SC5289) Drive amplifier(Q52: 2SK3475) 0.495–29.995 MHz RF amplifier (Q302: 2SC5006) 75.995–229.995 MHz RF amplifier (Q351: 3SK320) R3 regulator(Q353: XP4312) 29.995–75.995 MHz RF amplifier (Q303: 2SC5006) 629...
Page 8 - Removing the rear panel
3 - 1 SECTION 3 DISASSEMBLY INSTRUCTIONS 1. Removing the rear panel 2. Removing the LOGIC unit 3. Removing the AF unit 4. Removing the RF unit q Unscrew 1 screw A (M2 × 4 mm, black) . w Unscrew 2 screws B (M2 × 20 mm, black), and 4 screws C (M2 × 6 mm, black) from the rear panel. e Take off the rear...
Page 9 - SECTION 4 CIRCUIT DESCRIPTION; -1 RECEIVER CIRCUITS; • TRIPLEXER AND ANTENNA SWITCHING CIRCUITS
SECTION 4 CIRCUIT DESCRIPTION 4 - 1 4-1 RECEIVER CIRCUITS 4-1-1 TRIPLEXER CIRCUIT (RF UNIT) The transceiver has a triplexer (low-pass and bandpass fil-ters) on the first stage from the antenna switching diode toseparate the signals. • RF signals 0.495 MHz–75.995 MHzThe 0.495 MHz–75.995 MHz RF signal...
Page 10 - • RF CIRCUIT
4 - 2 (3) 76.0 MHz–229.995 MHz RF CIRCUITThe signals from the antenna switching circuit pass throughthe attenuator (D351), and then applied to the bandpass fil-ter (D352, D353, L351, L352) to suppress unwanted signals.The signals pass through the bandpass filter (D354–D356,D359, L354, L355, L357, L3...
Page 11 - • 2ND IF AND DEMODULATOR CIRCUIT
4 - 3 (1) AM DETECTOR CIRCUITThe filtered signals are applied to the AM detector circuit(Q201, Q202) to demodulate the 2nd IF signal into the AM AFsignals. (2) FM AND WFM DETECTOR CIRCUITThe filtered signals are applied to the limiter amplifier sectionin the FM IF IC (IC151, pin 5), and then applied...
Page 12 - -2 TRANSMITTER CIRCUITS
4 - 4 4-1-8 AGC CIRCUIT (AF AND RF UNITS) The AGC (Automatic Gain Control) circuit reduce signal fad-ing and keeps the audio output level constant. A portion of AF signals from the AM detector circuit (Q201)are applied to the amplifier (Q202). The amplified DC voltagefrom the Q202, pin 4 is applied ...
Page 13 - • APC CIRCUIT
4 - 5 4-2-5 APC CIRCUIT (RF UNIT) The APC circuit protects the power amplifier from a mis-matched output load and stabilizes the output power. TheAPC circuit is designed to use VHF and UHF bands com-monly. The APC sensor (R109) detects driving current from the drivevoltage at the drive (Q52) and pow...
Page 14 - • PLL CIRCUIT
4 - 6 • 430 MHz VCO CIRCUITThe oscillated signal at the 430 MHz VCO circuit (Q4, Q5,D3) is amplified at two buffer amplifiers (Q7, Q11), and isthen applied to the PLL IC (IC201, pin 19). The signal is divid-ed by serial data from the CPU (LOGIC unit; IC1) and phase-detected with the divided referenc...
Page 15 - -4 POWER SUPPLY CIRCUITS; VOLTAGE LINE
4 - 7 LINE HV VCC CPU3 +3C +3 +10V AFV R3 R3V T3 DESCRIPTION The voltage from the external power supply orattached battery pack. The same voltage as the “HV” line (externalpower supply or battery pack). Common 3 V converted from the “VCC” line byCPU3 regulator IC (LOGIC unit; IC141). The out-put vol...
Page 18 - SECTION 5
5 - 1 5-1 PREPARATION Some adjustments must be adjusted on the adjustment mode. When entering the adjustment mode, the 68 k Ω terminator (shown at page 5-2) is required. ‘ ‘ REQUIRED TEST EQUIPMENT ‘ ‘ ENTERING THE ADJUSTMENT MODE q Connect a 68 k Ω terminator to the [SP] jack. w Push and hold the [...
Page 19 - • CONNECTION
5 - 2 to [MIC] to the antenna connector RF power meter 0.1 10 W/50 Frequency counter Attenuator 40 dB or 50 dB FM deviation meter Standard signal generator 0.1 V to 32 mV ( 127 dBm to 17 dBm) Audio generator CAUTION: DO NOT transmit while an SSG is connected to the antenna connector. Optional SMA BN...
Page 20 - -2 TRIMMER ADJUSTMENT
5 - 3 5-2 TRIMMER ADJUSTMENT The following adjustment must be performed on the normal mode. PLL LOCKVOLTAGE POWERBALANCE ADJUSTMENT ADJUSTMENT ADJUSTMENT CONDITION MEASUREMENT VALUE POINT UNIT LOCATION UNIT ADJUST 1 2 3 4 5 6 1 2 3 4 5 • Displayed frequency : 30.000 MHz • Mode : FM • Receiving • Dis...
Page 22 - -3 ADJUSTMENT MODE ADJUSTMENTS
5 - 5 5-3 ADJUSTMENT MODE ADJUSTMENTS The following adjustment must be performed at “ADJUSTMENT MODE”. REFERENCEFREQUENCY OUTPUTPOWER(11V 50 MHzHigh power) (11V 145 MHzHigh power) (11V 440 MHzHigh power) (11V 50 MHzLow power) (11V 145 MHzLow power) ADJUSTMENT ADJUSTMENT ADJUSTMENT CONDITION MEASUREM...
Page 42 - Note
7 - 2 MP11 (R) MP10 (R) MP8 (R) MP18 (R) MP29 (C) MP30 (C) MP31 (C) MP9 (C) S251(A) MP21 (C) MP3 (C) MP15 (C) MP6 (C) MP8 (L) MP12 (L) MP11 (C) MP22 (C) MP12 (C) MP24 (C) MP24 (C) MP5 (C) MP2 (C) MP1 (C) MP12 (C) MP25 (C) MP8 (C) MP26 (C) MP4 (C) MP10 (C) MP9 (R) MP2 (R) MP6 (R) MP1 (R) MP1 (V) MP2 ...
Page 43 - - 1 TRANSISTORS AND FETS
8 - 1 SECTION PARTS LIST SECTION 8 SEMI-CONDUCTOR INFORMATION 8 - 1 TRANSISTORS AND FETS 8 - 2 DIODES NAME SYMBOL INSIDE VIEW 1SS364 BF MA132WK MU C A1 A2 1SS362 C3 1SS372 N9 MA133 MP A C MA6S121 M2D A1 C1 A2 C2 A3 C3 1SV307 TX A C MA132HK M3N A C 1SV271 TG 1SV290 TJ 1SV308 TX HVC132 P2 HVC136 TRF P...
Page 44 - SECTION 9
MC1 MICROPHONE PWR BAND D 1 V ↔ D 2 TONE 3 H/L MODE SCAN VFO MHZ 4 DUP 5 SKIP 6 M.N 0 RIT MR S.MW 7 TSCAN 8 SET 9 TS . DTMF.M CALL TV LOCK The combination of this page and the next page shows the unit layout in the same configuration as the actual P.C. Board. 9 - 1 9 - 1 LOGIC UNIT • TOP VIEW SECTIO...
Page 45 - LOGIC unit
1 1 2 39 40 2 39 40 GND INTSP CK PDAUL AM IOSTB DATA DICK REMO V3C V1C NOISE BEEP HV VOLC +3C AFV VMOD CHG GND +10V WXALT PLSTB WFM TXC DASTB DIUD R3C SD V2C VSFT EXTM MUTE VCC DETO +3 XMOD PATMP GND GND SQL PTT to AF unit J251 SP1 W2 (L) W2 (L) The combination of this page and the previous page sho...
Page 47 - RF unit
The combination of this page and the previous page shows the unit layout in the same configuration as the actual P.C. Board. RF unit • BOTTOM VIEW 9 - 4
Page 48 - VCO UNIT
9 - 5 9 - 3 AF UNIT • TOP VIEW VCO UNIT • TOP VIEW 1 2 39 40 3 3 1 2 4 2 1 DN E UP to S251 40 39 2 1 GNDCHG VMOD AFV +3C VOLC HV BEEP NOISE V1CV3C REMO DICK DATA IOSTB AM PDA/UL CK INTSP GND to LOGIC unit J1 EXT.MIC J252 EXT.SP REMOTO J253 J251 GNDGND PATMP XMOD +3 DETO VCC MUTE EXTM VSHFT V2C SD R3...
Page 49 - AF unit
9 - 6 VCO UNIT • BOTTOM VIEW 1 2 3 2 1 3 4 S251 S253 S252 UP E DN 1 15 30 16 to RF unit J251 J51 CK DATA PLSTB DASTB T43T50T14 B4C AGC B1C VCC B5B3 GND REF PDA/UL VMOD HV VSHFT +3 PATMP B2C +10V BSFT V2 FSET V3V1 IF CHG The combination of this page and the previous page shows the unit layout in the ...
Page 50 - BLOCK DIAGRAM; CPU
10 -1 SECTION 10 BLOCK DIAGRAM CPU LCD LPF +3 REG LPF LPF EEPROM KEY INITMATRIX HVSENS TXSENS MICMUTE MICAMP DEVCHANGE MODSW CT/DTSW LEDCTRL LEDCTRL LEDCTRL LED LED LED LED3REG +3CREG CPU3REG CHG RESET PCON CHGC CPU3 CHG CHG CHG HV PATMP VCC CT3SW MIC3SW CLONEBUFF INTSP VMOD XMOD MUTE DETO REMO +3C ...
Page 51 - AF UNIT; RF UNIT
10 - 2 AF UNIT CHASSIS RF UNIT VCO UNIT PATMP WXALT ANT LPF LPF LPF HPF HPF HPF ANT SW ANT SW ANT SW LPF BPF HPF AMP LPF DRIVE AMP DRIVE PRE BUFF TX/RX SW BPF BPF BPF BPF BPF RF AMP RF AMP RF AMP RF AMP RF AMP BPF BPF RF AMP RF AMP BPF BPF BPF BPF IF AMP BPF AM DET LPF AF AMP AF MUTE AF AMP HPF LO A...
Page 52 - VOLTAGE DIAGRAM
11 - 1 11 - 1 LOGIC UNIT SECTION 11 VOLTAGE DIAGRAM AFON CPUHV PTT +3CPU +3 VIN MUTE MICC PCON CHGC ESIO ECK CTSEL LED3 CTCIN +10V CTCOUT LA LB LC C8868p C50.001 R27 47k C900.001 C2022p R5368k R17 1k R9110k C4011 R14610k S1008 S1018 D141MA2S111 S1021 C951 R1447k R281k C961 S1007 R1010k S1016 R33322k...
Page 57 - MULTIBAND FM TRANSCEIVER
S-13903MZ-C1 2002 Icom Inc. 1-1-32, Kamiminami, Hirano-ku, Osaka 547-0003, Japan MULTIBAND FM TRANSCEIVER iC-t90a iC-t90a IC-T90A (1,4)
