Table Of Contents - Icom IC-25A Maintenance Manual

Table of Contents

Contents2
Specifications3
Controls And Their Functions4
Front Panel4
Product View And Control5
Rear Panel6
Under The Top Cover6
Inside Views7
Main Unit Side7
Pll Unit Side7
Block Diagram8
Operation9
Receiver9
Main Unit (Rf Circuitry)9
Main Unit (If Circuitry)9
Transmitter10
Microphone Amplification And Modulation Unit10
Band-Pass Filter And Younger Stage (Ygr) Unit10
Main Unit (Af-Amplification Circuitry)10
Pll Unit Block Diagram11
Alc Unit11
Power-Supply Unit11
Local-Oscillator Circuitry12
Pll Mixer Circuitry12
Driver Unit Block Diagram13
Loop Filter Circuitry13
Vco And Buffer-Amplification Circuitry13
Transmission Muting Circuitry13
Main Functions Of Logic Unit Ic's Transistors And Diodes14
Operation Of Logic Unit Ic6 (Mb14025)14
Up/Down, Scan And External Up/Down Control Circuitry15
Frequency Up/Down Circuitry15
Microphone Up/Down And Scan Control Circuitry16
Priority-Control Circuitry17
Scan Operation When Scan Start/Stop Switch Is On18
Cpu Input-Control And Matrix Circuitry19
Cpu And Output21
Logic Unit Ic's22
Order Of Disassembly23
Front Panel Controls25
Removal Of Front Frame And Pushbuttons27
Replacement Of Front Panel Pushbuttons28
Replacement Of Front Panel Controls29
Disassembly Of Rear Panel30
Pll Unit Wiring32
Main Unit Wiring33
Removal Of Circuit Boards34
Measuring Instruments For Adjustments35
Pll And Driver Unit Parts Layout (Pll Adjustment)36
Receiver Adjustments37
Measuring Instruments For Adjustment37
Reception Sensitivity Adjustment37
Af Output Check37
Main Unit Parts Layout (Reception Adjustment)38
Notes For Transmitter Adjustment39
Measuring Instrument For Adjustment39
Connection Of Measuring Instruments39
Main Unit Parts Layout (Transmission Adjustment)40
Modulation Adjustment41
Main Unit Parts Layout (Modulation Adjustment)42
Pll Unit Circuit Diagram And Voltage Chart43
Main Unit Circuit Diagram And Voltage Chart45
Driver (Logic) Unit47
Ef Unit Circuit Diagram49
Pa Unit Circuit Diagram And Voltage Chart51
Troubleshooting Guide52
Parts List57
Pll Unit61
Driver Unit62
Ic Ratings64
Tc-9123P (Fm/Am Synthesizer Tuner Pll)64
Pin Connection64
Maximum Rating64
Tc-5082 (Oscillator And 10-Stage Divider)65
Ba401 (Fm/If Limiter)65
Mjm4558D (Dual Low Noise Amp)65
Pc2002 (5.4-W Audio Power Amp)66
Pc577H (Fm-If Amplifier)66
Schematic Diagram67
Ef Unit71
Board Layout72
Pll Driver Unit73
Main Unit74
Pa Unit75
Unit Layout76