Icom IC-25A Manuals

Icom IC-25A Manuals

Manuals and User Guides for Icom IC-25A. We have 6 Icom IC-25A manuals available for free PDF download: Maintenance Manual, Instruction Manual

Icom IC-25A Maintenance Manual

Icom IC-25A Maintenance Manual (77 pages)

144 MHz

Brand: Icom | Category: Transceiver | Size: 13 MB

Table of Contents

Contents
2
Specifications
3
Controls and Their Functions
4
Front Panel
4
Product View and Control
5
Rear Panel
6
Under the Top Cover
6
Inside Views
7
Main Unit Side
7
PLL Unit Side
7
Block Diagram
8
Operation
9
Receiver
9
Main Unit (RF Circuitry)
9
Main Unit (if Circuitry)
9
Transmitter
10
Microphone Amplification and Modulation Unit
10
Band-Pass Filter and Younger Stage (YGR) Unit
10
Main Unit (AF-Amplification Circuitry)
10
PLL Unit Block Diagram
11
ALC Unit
11
Power-Supply Unit
11
Local-Oscillator Circuitry
12
PLL Mixer Circuitry
12
Driver Unit Block Diagram
13
Loop Filter Circuitry
13
VCO and Buffer-Amplification Circuitry
13
Transmission Muting Circuitry
13
Main Functions of Logic Unit IC's Transistors and Diodes
14
Operation of Logic Unit IC6 (MB14025)
14
Up/Down, Scan and External Up/Down Control Circuitry
15
Frequency Up/Down Circuitry
15
Microphone Up/Down and Scan Control Circuitry
16
Priority-Control Circuitry
17
Scan Operation When Scan Start/Stop Switch Is on
18
CPU Input-Control and Matrix Circuitry
19
CPU and Output
21
Logic Unit IC's
22
Order of Disassembly
23
Front Panel Controls
25
Removal of Front Frame and Pushbuttons
27
Replacement of Front Panel Pushbuttons
28
Replacement of Front Panel Controls
29
Disassembly of Rear Panel
30
PLL Unit Wiring
32
Main Unit Wiring
33
Removal of Circuit Boards
34
Measuring Instruments for Adjustments
35
PLL and Driver Unit Parts Layout (PLL Adjustment)
36
Receiver Adjustments
37
Measuring Instruments for Adjustment
37
Reception Sensitivity Adjustment
37
AF Output Check
37
Main Unit Parts Layout (Reception Adjustment)
38
Notes for Transmitter Adjustment
39
Measuring Instrument for Adjustment
39
Connection of Measuring Instruments
39
Main Unit Parts Layout (Transmission Adjustment)
40
Modulation Adjustment
41
Main Unit Parts Layout (Modulation Adjustment)
42
PLL Unit Circuit Diagram and Voltage Chart
43
Main Unit Circuit Diagram and Voltage Chart
45
Driver (Logic) Unit
47
EF Unit Circuit Diagram
49
PA Unit Circuit Diagram and Voltage Chart
51
Troubleshooting Guide
52
Parts List
57
PLL Unit
61
Driver Unit
62
IC Ratings
64
TC-9123P (FM/AM Synthesizer Tuner PLL)
64
Pin Connection
64
Maximum Rating
64
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 Diagram
67
EF Unit
71
Board Layout
72
PLL Driver Unit
73
Main Unit
74
PA Unit
75
Unit Layout
76

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