Codan 8525B Series Technical & Service Manual
  1. Manuals
  2. Brands
  3. Codan Manuals
  4. Transceiver
  5. 8525B Series
  6. Technical & service manual
Codan 8525B Series Technical & Service Manual

Codan 8525B Series Technical & Service Manual

Hf ssb transceiver
Hide thumbs Also See for 8525B Series:
Table of Contents

Advertisement

Quick Links

Download this manual See also: Handbook
HF SSB Transceiver
8525B/8528 series
Technical Service Manual
Volume 1
© 1989 Codan Pty Ltd.
ACN 007 590 605
Order code 15-02036
Issue 6, November 1995

Advertisement

Table of Contents
loading

Related Manuals for Codan 8525B Series

Summary of Contents for Codan 8525B Series

  • Page 1 HF SSB Transceiver 8525B/8528 series Technical Service Manual Volume 1 © 1989 Codan Pty Ltd. ACN 007 590 605 Order code 15-02036 Issue 6, November 1995...
  • Page 2 Head Office Codan Pty Ltd ACN 007 590 605 81 Graves Street Newton South Australia 5074 International +61 8 8305 0311 Facsimile +61 8 8305 0411 Marketing Offices Codan (U.K.) Ltd Gostrey House Union Road Farnham, Surrey GU9 7PT United Kingdom...

  • Page 3: Table Of Contents

    Table of Contents 1 General Information Introduction ......................1-1 Specifications .....................1-2 1.2.1 General ....................1-2 1.2.2 Receiver...................1-4 1.2.3 Transmitter ..................1-6 1.2.4 Rear Panel Connectors ..............1-7 1.2.5 Front Panel Connector..............1-10 Options and Accessories ..................1-11 1.3.1 Options ..................1-11 1.3.2 Accessories..................1-12 Abbreviations ....................1-13 Circuit Reference Designations................1-20 Units .........................1-21 Unit Multipliers ....................1-21 2 Block Diagram...
  • Page 4 ii Table of Contents 8525B/8528 Technical Service Manual 4 Technical Description Control and Supply Voltages................4-1 4.1.1 Supply Voltages ................4-1 4.1.2 Power and Control Lines..............4-2 4.1.3 Overvoltage and Reverse Voltage Protection........4-2 4.1.4 Transceiver Power On/Off ..............4-2 4.1 5 High Power Transceiver Protection and Power On/Off ....4-3 Receiver......................4-4 4.2.1 Input Filters ..................4-4 4.2.2 Mixers, First IF Amplifiers and Filters ...........4-4...
  • Page 5 8525B/8528 Technical Service Manual Table of Contents iii Microprocessor Controller PCB (04-02451 & 04-03031)........4-12 4.5.1 Microcontroller Bus ..............4-12 4.5.2 Internal I C Bus ................4-13 4.5.3 External Bus ..................4-14 4.5.4 Reset and Watchdog Circuit............4-14 4.5.5 RS-232 Port (ALE Option Only)...........4-14 Motherboard and Chassis (02-02453) ..............4-15 4.6.1 Power Supplies................4-15 4.6.2 Antenna Control Facility...............4-15 4.6.3 Extended or Remote Control—Option R ........4-15...
  • Page 6 iv Table of Contents 8525B/8528 Technical Service Manual PA and Filters (04-02452)................4-24 4.9.1 Introduction ...................4-24 4.9.2 PTT Control...................4-24 4.9.3 Gain Control Stage ................4-24 4.9.4 Pre-Driver Stages ................4-24 4.9.5 Driver Stage...................4-25 4.9.6 Output Stage and Bias Regulator ..........4-25 4.9.7 Output Filters and Control.............4-25 4.9.8 ALC Control..................4-26 4.9.9 Transmit Indicator .................4-27 4.10 PA Exciter Interface ..................4-27...
  • Page 7 8525B/8528 Technical Service Manual Table of Contents v 4.14 Options ......................4-36 4.14.1 F—Fan Assembly................4-36 4.14.2 LU—Switched LSB Operation............4-36 4.14.3 L—Lower Sideband Operation .............4-37 4.14.4 M—CW Facility................4-37 4.14.5 PH—Headphone Output ...............4-37 4.14.6 R—Extended/Remote Control Interface ........4-37 4.14.7 AD—Antenna Driver ..............4-37 5 Operating Instructions 6 Maintenance General .......................6-1 6.1.1 CMOS Devices................6-1...
  • Page 8 vi Table of Contents 8525B/8528 Technical Service Manual Dismantling and Re-assembly................6-9 6.3.1 General ....................6-9 6.3.2 Top and Bottom Covers ..............6-9 6.3.3 Circuit Board Removal..............6-9 6.3.4 PA and Filter Assembly ..............6-10 6.3.5 Replacement of PA Transistors.............6-11 6.3.6 Replacement of Escutcheon or Switch Substrate ......6-12 7 Adjustments Introduction ......................7-1 Channel Addition (EPROM Replacement) ............7-1...
  • Page 9 8525B/8528 Technical Service Manual Table of Contents vii 7.3.17 Selective Call Code Settings (8525B) ...........7-14 7.3.18 Message Length Setting ..............7-15 7.3.19 Selective Call Code Settings (8528)..........7-15 Receiver Performance Checks................7-16 7.4.1 Sensitivity and Signal + Noise to Noise Ratio ......7-16 7.4.2 AGC Check ...................7-16 7.4.3 Audio Output.................7-16 7.4.4 Selectivity (USB Operation)............7-16 7.4.5 Clarifier Operation ................7-16...

  • Page 10: Issue 6 Publication No:

    viii Table of Contents 8525B/8528 Technical Service Manual Issue 6 Publication No: 15-02036...

  • Page 11: General Information

    8525B/8528 Technical Service Manual General Information 1.1 Introduction The Type 8525B Series and 8528 Series transceivers feature synthesized frequency generation and have sealed membrane controls. The two series differ only in control and display facilities. All differences are in the front panel and the controlling EPROM.

  • Page 12: Specifications

    13.6V DC, 50Ω source and load, and 25°C ambient temperature (unless otherwise specified). 1.2.1 General Specifications 8525B series; 8528 series including cover 8528S and H versions. (H transmission specifications included in a separate Technical Service Manual (code 2037), covering the 4402 and 4404 PA units).
  • Page 13 8525B/8528 Technical Service Manual General Information 1-3 Oven warm-up 1 minute. time Controls Sealed membrane switches. Indicators Refer to illustrations for details. 8525B: All indicators except Tx automatically dimmed for low ambient light levels. 8528: All indicators except Tx may be manually dimmed by front panel controls if required.

  • Page 14: Receiver

    1-4 General Information 8525B/8528 Technical Service Manual Cooling Convection or fan (Option F). Size and weight Transceiver only: 250mm W x 78mm H x 350mm D; 3.41kg With mounting cradle: 270mm W x 90mm H x 350mm D; 3.92kg 8530 Control Head: 180mm W x 65mm H x 70mm D With mounting bracket: 190mm W x 78mm H x 70mm D;...
  • Page 15 8525B/8528 Technical Service Manual General Information 1-5 Desensitisation 10dB SINAD reduced to 7dB SINAD. –1 and +4.4kHz ref SCF (USB) 62(55)dB. ±10kHz 85(80)dB. ±50kHz 100(95)dB. Image Rejection Better than 90(80)dB Spurious Better than 90(70)dB. Responses Self generated signals >0.25µV PD; 6.6MHz, 9.998MHz, 13.2MHz, 19.8MHz, 26.4MHz.

  • Page 16: Transmitter

    1-6 General Information 8525B/8528 Technical Service Manual 1.2.3 Transmitter Power Output 100W PEP at 2MHz falling linearly with frequency to 90W PEP at 24MHz ±0.5dB. Land Marine 125W PEP at 2MHz falling linearly with frequency to 90W PEP at 24MHz ±1dB. CW or single tone: approximately 60% of PEP with average PEP control.

  • Page 17: Rear Panel Connectors

    8525B/8528 Technical Service Manual General Information 1-7 A 10dB increase in input level above compression threshold produces less than 0.5dB increase in power output. Maximum ALC range greater than 30dB. ALC attack time approximately 1ms. Residual Noise 65(55)dB below PEP in 3kHz channel. Transmitter Noise Transmitter noise output below cut-off Floor...
  • Page 18 1-8 General Information 8525B/8528 Technical Service Manual Option R (15-way, D-type Plug) Pin Number Function Signal Level Loudspeaker Ref Spec Remote PTT 0 Volts = PTT Receiver Audio Special * Output Power On Momentary 0V for Power ON Data 5 Volt Logic Data Line Enable 5 Volt Logic Clock...
  • Page 19 8525B/8528 Technical Service Manual General Information 1-9 Option PS Note: Option PS cannot be fitted with internal option SDE or SDEM. Pin Number Function Signal Level Ground Rx FSK Tones Nom. 1.5Vpp (From Output 2k ohms) FSK Tx Tones Input 3Vpp (22k ohm Input Impedance) Quiet Line...

  • Page 20: Front Panel Connector

    1-10 General Information 8525B/8528 Technical Service Manual 1.2.5 Front Panel Connector Microphone Connector Pin Number Function PTT ground PTT active low Microphone input Microphone ground Speaker connection* Audio output Audio output *Linked to pin 7 for front panel speaker operation. Issue 6 Publication No: 15-02036...

  • Page 21: Options And Accessories

    8525B/8528 Technical Service Manual General Information 1-11 1.3 Options and Accessories 1.3.1 Options The following is a list of the options available with brief descriptions. The references in brackets indicate more detailed descriptions will be found in those sections of this manual. Fit antenna driver interface for 8558 automatic tuning whip antenna.

  • Page 22: Accessories

    1-12 General Information 8525B/8528 Technical Service Manual 1.3.2 Accessories The following is a list of the accessories available. Code Vehicle installation hardware kit. Marine suppression kit. Vehicle mounting cradle—front entry. Vehicle mounting cradle—top/bottom entry. Supplied complete with transceiver DC power cable (6 metres).

  • Page 23: Abbreviations

    8525B/8528 Technical Service Manual General Information 1-13 1.4 Abbreviations Analog to digital Across flats (hexagon) Alternating Current ACIA Asynchronous Communication Interface Adapter Adjust Audio Frequency Automatic Frequency Control Automatic Gain Control Automatic Level Control Absorption Limited Frequency Amplitude Modulation ASCII American Standard Code for Information Interchange ASSY...
  • Page 24 1-14 General Information 8525B/8528 Technical Service Manual Continuous Wave, Carrier Wave or Clockwise Digital to Analog Direct Current DEMUX Demultiplexer Direct Memory Access DPDT Double Pole, Double Throw DPST Double Pole, Single Throw Drawing Double Sideband Diode Transistor Logic Digital Voltmeter Decibel Decibel relative to 1mW EAPROM...
  • Page 25 8525B/8528 Technical Service Manual General Information 1-15 High Pass Filter I/COM Intercom Interface Input Output Input Intermediate Frequency Intermodulation Distortion Internal Independent Sideband JFET Junction Field Effect Transistor Single Sideband Suppressed Carrier Telephony Emission Inductance-Capacitance Liquid Crystal Display Light Dependent Resistor Light Emitting Diode Low Frequency Linear Law...
  • Page 26 1-16 General Information 8525B/8528 Technical Service Manual Most Significant Bit Medium Scale Integration Maximum Useable Frequency Multiplex, Multiplexer Normally Closed Normally Open Not Connected NMOS N Type Metal Oxide Semiconductor Normal Operating Level Nominal NORM Normal Zero Temperature Coefficient Negative Temperature Coefficient Open Circuit Outdoor Unit Orthomode Transducer...
  • Page 27 8525B/8528 Technical Service Manual General Information 1-17 Potentiometer Peak to Peak Parts per Million PROM Programmable Read Only Memory Power Supply Unit Positive Temperature Coefficient (Resistor) Push To Talk Programmable Unijunction Transistor Pulse Width Modulation Random Access Memory Remote Control Resistance-Capacitance Remote Control Unit Reference...
  • Page 28 1-18 General Information 8525B/8528 Technical Service Manual Single Sideband STTL Schottky Transistor Transistor Logic Standing Wave Ratio SYNC Synchronisation SYNTH Synthesizer Transmit Receive Temperature Coefficient TCVR Transceiver Tinned Copper Wire TCXO Temperature Compensated Crystal Oscillator TVRO Television Receive Only Time Division Multiplex Total Harmonic Distortion TRIG Trigger...
  • Page 29 8525B/8528 Technical Service Manual General Information 1-19 Voice Operated Switch VSWR Voltage Standing Wave Ratio Volume Unit With Respect To Weight Extension XTND Extend λ Wavelength Positive Negative ∅ Phase, Diameter in mm Note: EMF is the source voltage behind the output resistance (Rs) and is independent of the signal generator loading.

  • Page 30: Circuit Reference Designations

    1-20 General Information 8525B/8528 Technical Service Manual 1.5 Circuit Reference Designations Assembly Transducer—Microphone, Loudspeaker, etc Capacitor Diode—small signal and power Heating device Protection device—Fuse, etc Generator—battery, etc Signalling/indicating device—Lamp. LED, Buzzer, Integrated Circuit, thick film hybrid Jack socket Relay, key switch Inductor Indicating device—meter, etc Plug...

  • Page 31: Units

    8525B/8528 Technical Service Manual General Information 1-21 1.6 Units Ampere metre Celsius (degrees) minute Coulomb Newton Farad Pascal gram Siemen hour second Henry Tesla Hertz Volt Joule Watt Kelvin (degrees) Weber Ω litre Ohms 1.7 Unit Multipliers tera one million million giga one thousand million mega...
  • Page 32 1-22 General Information 8525B/8528 Technical Service Manual Issue 6 Publication No: 15-02036...

  • Page 33: Brief Description

    8525B/8528 Technical Service Manual Brief Description 3.1 General This description should be read in conjunction with Block Diagram 03-00636. The same frequency conversions are used in both transmit and receive modes, therefore many circuits are common to both modes of operation. Signal routing is determined by switching and control voltages according to the mode selected.

  • Page 34: Transmit

    3-2 Brief Description 8525B/8528 Technical Service Manual 3.3 Transmit The audio signal is amplified and levelled in the microphone amplifier and compressor, then fed to the balanced modulator where it is mixed with the 1650kHz (USB) or 1647kHz (LSB) local oscillator to produce a DSB signal. The resulting signal is filtered by the 2.5kHz crystal filter to produce the SSB signal (USB or LSB) required for transmission.

  • Page 35: Display, Control And Switching

    8525B/8528 Technical Service Manual Brief Description 3-3 3.5 Display, Control and Switching All the transceiver functions are microprocessor controlled with the required channel frequencies, facilities, etc being preprogrammed into an Erasable Programmable Read Only Memory (EPROM). The front-panel and extended (8530, 8532 or 8531S) control head displays, and switch-pads are controlled via a four-wire serial bus.
  • Page 36 3-4 Brief Description 8525B/8528 Technical Service Manual Issue 6 Publication No: 15-02036...

  • Page 37: Technical Description

    8525B/8528 Technical Service Manual Technical Description This section of the manual contains a detailed description of the circuitry used in the land and marine transceivers and associated control heads. Unless otherwise stated, the description applies equally to the 8525B, 8528 and 8528S transceivers.

  • Page 38: Power And Control Lines

    4-2 Technical Description 8525B/8528 Technical Service Manual 4.1.2 Power and Control Lines By controlling relay K1 on the Motherboard, the microprocessor on the Microprocessor Controller PCB generates two switched +10V power and control lines designated as the ‘C’ and ‘D’ rails. These rails are defined as follows: •...

  • Page 39: High Power Transceiver Protection And Power On/Off

    8525B/8528 Technical Service Manual Technical Description 4-3 Pressing the power on/off pad with relay K2 set to ‘on’ has no effect on V2 on the Motherboard. However, via the front panel I C bus control, the microprocessor grounds the Power Off line, J3 pin 5. This energises the ‘off’ coil of K2, toggling the relay back to its ‘off’...

  • Page 40: Receiver

    4-4 Technical Description 8525B/8528 Technical Service Manual 4.2 Receiver 4.2.1 Input Filters (Refer 04-02452) The receiver input signal is passed through the PA low-pass filter selected by the PA band line, the transmit/receive relay K6 and the 2MHz high-pass broadcast filter to the RF, Mixer & Dual Synthesizer PCB. Option LF adds a 1nF capacitor C111 in parallel with C47, reducing the broadcast filters passband to 1.6MHz.

  • Page 41: Noise Blanker

    8525B/8528 Technical Service Manual Technical Description 4-5 4.2.3 Noise Blanker The 1650kHz IF signal is amplified by the RC coupled stages V15 and V18 and fed to the tuned collector amplifier V20. V21 is an active rectifier. Noise bursts produce negative going pulses at the emitter of V21 which drives the monostable flip-flop V25 and V26.

  • Page 42: Audio Mute

    4-6 Technical Description 8525B/8528 Technical Service Manual 4.2.6 Audio Mute The audio from the output of IC4a is looped back through the Motherboard to the Audio and IF 1650kHz PCB and applied to the audio mute input (R63/C37) and the mute gate (V12). IC4b and IC3a are arranged as a squaring amplifier.

  • Page 43: Transmitter Exciter

    8525B/8528 Technical Service Manual Technical Description 4-7 4.3 Transmitter Exciter 4.3.1 Microphone Amplifier (Refer Dwg 04-02093) The input to the microphone amplifier is J1, pin 6. Transistor V7 is an audio clamp which is released only when the microphone PTT button is pressed. This prevents the microphone picking up background noise and sidetone from the loudspeaker when transmitting emergency calls etc.

  • Page 44: Crystal Filter

    4-8 Technical Description 8525B/8528 Technical Service Manual 4.3.3 Crystal Filter One sideband of the DSB signal from the modulator is selected by the crystal filter to give an SSB signal. During transmit, the C rail is at 0 Volts, and forces a low output from IC1b for maximum AGC to V2 and V3. Thus, none of the transmit signal passes through the IF Amplifier.

  • Page 45: Local Oscillators

    8525B/8528 Technical Service Manual Technical Description 4-9 4.4 Local Oscillators (04-02450) Two synthesized oscillators are used to drive the first and second mixers. The first oscillator operates between 45.250MHz and 75MHz in 2kHz steps to convert the 250kHz to 30MHz received signal to 45MHz for the first IF. The second oscillator operates between 43.352 and 43.350MHz in 10Hz steps to convert the 45MHz first IF to the 1650kHz second IF.

  • Page 46: Lock Signals

    4-10 Technical Description 8525B/8528 Technical Service Manual When the phase/frequency difference is considerable, e.g. immediately after a change of channel, the output from PDB (IC5 pin 2) consists of pulses with their mark:space ratio proportional to the difference. These are integrated by R82 and C123 to provide an input to IC2b.

  • Page 47: 1650/1647Khz Local Oscillators

    8525B/8528 Technical Service Manual Technical Description 4-11 4.4.5 1650/1647kHz Local Oscillators When receiving (or transmitting) a USB signal, a 1650kHz local oscillator is required. This is obtained by dividing the buffered oscillator output of IC7 (6.6MHz) by 4 in IC9. When receiving (or transmitting) an LSB signal, a 1647kHz local oscillator is required.

  • Page 48: Microprocessor Controller Pcb (04-02451 & 04-03031)

    4-12 Technical Description 8525B/8528 Technical Service Manual 4.5 Microprocessor Controller PCB (04-02451 and 04- 03031) Circuits on the Microprocessor Controller PCB govern the functions of the transceiver including the operator controls and displays. The microcontroller on the board accepts inputs from within the transceiver and from the operator’s controls.
  • Page 49 8525B/8528 Technical Service Manual Technical Description 4-13 Write signals are inserted via D3 and D4 to maintain a steady square wave signal. Publication No: 15-02036 Issue 6...

  • Page 50: Internal I C Bus

    4-14 Technical Description 8525B/8528 Technical Service Manual 4.5.2 Internal I C Bus The internal I C bus consists of four lines: data, clock, interrupt and data-line enable. The data and clock lines operate as an I C bus; the data line carries data and address bits serially, with their transfer being synchronised by transitions on the clock line.

  • Page 51: External Bus

    8525B/8528 Technical Service Manual Technical Description 4-15 The clock and data lines are also taken to connector P1 for application to I/O ports in the Selective Calling PCB when this is fitted. Provision is made for all four lines of the bus to be connected via P3 to further I/O IC’s if required. 4.5.3 External Bus A second four-line bus is provided for connection to 8-bit I/O IC’s and...

  • Page 52: Motherboard And Chassis (02-02453)

    4-16 Technical Description 8525B/8528 Technical Service Manual 4.6 Motherboard and Chassis (04-02453) The Motherboard interconnects circuit boards which are mounted directly on it and provides connections to other assemblies mounted on the chassis. It also provides connections which link these assemblies to external connectors.

  • Page 53: External Microphone Audio Clamp

    8525B/8528 Technical Service Manual Technical Description 4-17 4.6.4 External Microphone Audio Clamp The audio input from the Remote Control connector at pin 11 P502 (Option R) is connected, via C102, R103, R101 and C101 to the Aux Compressor input of the Audio and IF 1650kHz PCB. FET V101 is normally biased on via R104 and R105, thus clamping the microphone input to ground.

  • Page 54: Agc Dump Circuit

    4.7 8525B Front Panels and Control Head (04-02579) The front panels of 8525B series transceivers and extended control heads are similar. Overlays on these panels contain sealed tactile membrane switches. A 2-digit numeric display and LED’s on a board behind the panel show through the appropriate part of the overlay when lit.

  • Page 55: Switch Matrix

    8525B/8528 Technical Service Manual Technical Description 4-19 4.7.2 Switch Matrix The switches on the panel overlay (substrate) form a 4 x 4 matrix. The row and column connections are taken to the Display PCB. (A table listing the switch functions and corresponding connections is given in Section 6.2.3.) The row connections are polled by the microprocessor, via IC2 by taking them to 0V one at a time.

  • Page 56: 8528 Front Panel And Control Head

    4-20 Technical Description 8525B/8528 Technical Service Manual 4.8 8528 Front Panel and Control Head The front panels of 8528 series transceivers and extended control heads are identical. Overlays on the panels contain sealed tactile membrane switches. A liquid crystal display (LCD) and light-emitting diode (LED) indicators on a board behind the panel show through the appropriate part of the overlay when activated.

  • Page 57: Indicator And Display Dimming

    8525B/8528 Technical Service Manual Technical Description 4-21 Six incandescent lamps, H1 to H6, are mounted behind the LCD to provide back-lighting so that the display can be read in low ambient light. V1 is mounted in a position which allows ambient light to fall on the transistor. Conduction of the transistor increases with the light, i.e.

  • Page 58: Switch Matrix

    The board used in the extended control head to compensate for the long lines connecting the head to the transceiver is the same as the one used for the same purpose in the 8525B series. (Refer to Para 4.7.4). 4.8.6...
  • Page 59 8525B/8528 Technical Service Manual Technical Description 4-23 The viewing angle is preset by the adjustment of R34. This sets the voltage applied to the non-inverting input of IC4a, while the voltage at the junction of R32 and D6 is applied to the inverting input. The output of IC4a is proportional to the difference between the two voltages.
  • Page 60 4-24 Technical Description 8525B/8528 Technical Service Manual Switches on the panel overlay (substrate) form a 4 x 6 matrix. The row and column connections are taken to the Display PCB. (A table listing the switch functions and the corresponding connections is given in Section 6.2.3.) In the Display PCB the row connections are polled by the microprocessor, via IC2, taking them to 0V one at a time.

  • Page 61: Pa And Filters (04-02452)

    8525B/8528 Technical Service Manual Technical Description 4-25 4.9 PA and Filters (04-02452) 4.9.1 Introduction 8528S Series transceivers may be fitted with a PA and Filter PCB, forming an internal PA stage, or with a PA Exciter Interface PCB for use with an external PA unit.

  • Page 62: Driver Stage

    4-26 Technical Description 8525B/8528 Technical Service Manual 4.9.5 Driver Stage The driver stage V16 and V17 is voltage driven from the secondary of T2 and with emitter resistors R52 to R55 provides a current drive to the output stage. L20, C78 and R56 provide damping for a harmonic resonance in T3. The bias for V16 and V17 is provided by the current of the pre-driver stages passing through the diode-connected transistor V13.

  • Page 63: Alc Control

    8525B/8528 Technical Service Manual Technical Description 4-27 4.9.8 ALC Control ALC control is provided from the following sources: • Forward power • Reflected power • Battery voltage • Low Power control (8528S only) • Heatsink over-temperature • Output stage collector swing. The ALC control inputs are applied to IC2a which provides a fast attack, slow decay control voltage to the base of V7.

  • Page 64: Transmit Indicator

    H suffixed to their type numbers on the rear panel. The PA Exciter Interface is designed for use with Codan Type 4402 or 4404 power amplifiers and is described in this section. The PCB fitted for the internal PA is described in Section 4.9.

  • Page 65: Transmit Amplifier

    The Scan, Tune and Tuned In control signals are also taken to and from the PA unit. 4.10.8 PA Unit Details of the Codan 4402 and 4404 PA Units are given a separate service manual Code 2037. Publication No: 15-02036...

  • Page 66: Selective Calling (04-02250)

    4-30 Technical Description 8525B/8528 Technical Service Manual 4.11 Selective Calling (04-02250) Selective calling facilities may be either internal to the 8525B or 8528, or by external control using option PS. It should be noted that option PS cannot be used when internal selective call is fitted. The following selective call variants are available: •...

  • Page 67: Selective Call Detection (04-02250)

    8525B/8528 Technical Service Manual Technical Description 4-31 4.11.2 Selective Call Detection (04-02250) The Selective Call PCB fitted for Options SDE and SDEM includes circuits for the detection of selective calling signals. The received audio is applied via J1 pin 2 to a band-pass filter formed by IC1a, IC1b and their associated components.

  • Page 68: Two-Tone Calling

    4-32 Technical Description 8525B/8528 Technical Service Manual 4.12 Two-Tone Calling System The two tone calling system consists of the transmission of two simultaneous audio tones. The difference frequency is detected to provide a narrow bandwidth independent of frequency shifts in the RF path. 4.12.1 Two-Tone Calling The call is initiated by pressing the Call pad on the front panel.
  • Page 69 8525B/8528 Technical Service Manual Technical Description 4-33 The two-tone audio signal is further filtered by a high pass filter formed by IC2b, IC3a and their associated components. The filter output is applied to a phase splitter V3, so that equal anti-phase waveforms are produced. Each of these is applied to one of the two transistors V4 and V5 which operate as a full-wave rectifier.

  • Page 70: Option Ps-External Signalling Interface

    4.13 Option PS—External Signalling Interface Connector J301 can be fitted to the transceiver rear panel to provide connection for Codan 8422 or 8511 Selective Call Controllers, radio teletype (RTTY) or other signalling equipment. When the option is fitted, J301 is connected to P301 on the Motherboard (refer to 04-02453) and components associated with the interface are installed on the board.

  • Page 71: Selective Call Scanning

    Technical Description 4-35 4.13.2 Selective Call Scanning With Option PS fitted and Codan 8422 or 8511 units connected to J301, the scan facility of the transceiver can be used to scan up to eight channels for selective calls. This mode of operation is initiated by selecting Scan on the transceiver front panel and Mute on the external equipment.

  • Page 72: Rtty-Arq Mode

    4-36 Technical Description 8525B/8528 Technical Service Manual Figure 4.1 Selective Call Scanning 4.13.3 RTTY—ARQ Mode With Option PS fitted the transceiver can be used for ARQ mode teletype transmission and reception. The teletype interfacing equipment is connected to J301 in the same way as the selective calling equipment. Refer to the table in section 1.2.4 for the pin connections and the levels acceptable for each function.

  • Page 73: Options

    8525B/8528 Technical Service Manual Technical Description 4-37 4.14 Options Options may be fitted to the transceivers as described in the sections which follow. 4.14.1 F—Fan Assembly Option F is a factory-fitted assembly containing an axial flow fan and its control circuit. Mounted over the heatsink the fan enhances the heat dissipation of the transmitter.

  • Page 74: L-Lower Sideband Operation

    4.14.7 AD—Antenna Driver Option AD enables Type 8525B/8528 Series Transceivers to be used with Codan Automatic Tuning Whip Antennas Type 8558 while still retaining the capability of using antennas with preset tuning. The option consists of a single PCB (Antenna Driver PCB Assembly (08-04285).
  • Page 75 8525B/8528 Technical Service Manual Technical Description 4-39 When the Tune pad on the transceiver control panel is pressed the microprocessor causes some RF, at the required transmission frequency, to be applied to the antenna. At the same time the microprocessor prepares the IO device, IC3, to respond to the VSWR measurement.
  • Page 76 4-40 Technical Description 8525B/8528 Technical Service Manual On completion of the tune operation a positive voltage is applied to the Brake input (J1 pin 6). This switches on V1 which bypasses R1 to lower the output of IC1 to approximately 1.3V. This is applied to the antenna motor windings.

  • Page 77: Operating Instructions

    8525B/8528 Technical Service Manual Operating Instructions Refer to the relevant Operator’s Instructions booklets. Publication No: 15-02036 Issue 6...
  • Page 78 5-2 Operating Instructions 8525B/8528 Technical Service Manual Issue 6 Publication No: 15-02036...

  • Page 79: Maintenance

    8525B/8528 Technical Service Manual Maintenance 6.1 General 6.1.1 CMOS Devices A number of Complementary Metal Oxide Semiconductor (CMOS) devices are used in the transceiver. Although protection is built into most of these, their extremely high open-circuit impedance makes them susceptible to damage from static charges.
  • Page 80 6-2 Maintenance 8525B/8528 Technical Service Manual • Unsoldering—When unsoldering use a solder-sucker or Solderwick to remove solder. DO NOT USE SHARP METAL TOOLS SUCH AS SCREWDRIVERS OR TWIST DRILLS AS THESE WILL DAMAGE THE PRINTED CIRCUIT TRACK. • Component substitution—Avoid unnecessary component substitution as this may damage the component, the circuit track or adjacent components.

  • Page 81: Transmitter Precautions

    8525B/8528 Technical Service Manual Maintenance 6-3 • Integrated circuit replacement—In some cases it is possible to desolder and remove components from the board without damage to the component or the board. However, integrated circuits with a large number of connections, mounted on double-sided circuit boards with plated-through holes are almost impossible to remove intact, and the operation is likely to damage the circuit boards.

  • Page 82: Fault Diagnosis

    6-4 Maintenance 8525B/8528 Technical Service Manual 6.2 Fault Diagnosis 6.2.1 General The removal and substitution of components may damage the components and/or the printed circuit boards. In some cases it is impossible to remove components without destroying them. It is important therefore to carry out as much fault diagnosis as possible with components in situ.

  • Page 83: Voltage Measurement

    8525B/8528 Technical Service Manual Maintenance 6-5 6.2.2 Voltage Measurement The circuit diagrams and the relevant circuit notes give voltages at various points under the various conditions to enable the faulty section of the transceiver to be located. The parameters listed below should always be checked first: 1.

  • Page 84: Front Panel Controls

    6-6 Maintenance 8525B/8528 Technical Service Manual 6.2.3 Front Panel Controls IN THE TEST WHICH FOLLOWS CARE MUST BE TAKEN WHEN MAKING CONTACT WITH THE CONNECTIONS TO THE SWITCH SUBSTRATE NOT TO SCRATCH THE SILVER PLATING. Lack of response to controls may be due to malfunction of one or more of the sealed membrane switches.

  • Page 85: Logic Levels

    8525B/8528 Technical Service Manual Maintenance 6-7 Front Panel Switch Tests (8525B) Connector Pin 8525B 1 - 5 Scan 1 - 6 Audio Mute 1 - 7 S’call Mute 1 - 8 Power On/Off 2 - 5 Tune 2 - 6 Mute off 2 - 7 USB/LSB...

  • Page 86: No Transmission

    6-8 Maintenance 8525B/8528 Technical Service Manual 6.2.6 No Transmission If no signal is transmitted, after confirming the supply voltages described in 6.2.2, a single tone approximately 1kHz at 20mV rms should be applied to the microphone input. The voltages to be expected in the transmit mode at various points with this input applied are shown in the circuit diagram.
  • Page 87 8525B/8528 Technical Service Manual Maintenance 6-9 Publication No: 15-02036 Issue 6...

  • Page 88: Dismantling And Re-Assembly

    6-10 Maintenance 8525B/8528 Technical Service Manual 6.3 Dismantling and Re-assembly 6.3.1 General It may be necessary to remove printed circuit boards from the transceiver in order to carry out certain repairs. The paragraphs which follow give instructions for the removal and re-installation of boards. While carrying out these the following general points should be observed: •...

  • Page 89: Pa And Filter Assembly

    8525B/8528 Technical Service Manual Maintenance 6-11 6.3.4 PA and Filter Assembly Note: The PA output transistors can be replaced without removing the board from the heat sink. Refer to para 6.3.5. The PA and Filter PCB (08-03021) can be removed as follows: 1.

  • Page 90: Replacement Of Pa Transistors

    6-12 Maintenance 8525B/8528 Technical Service Manual 11. Before re-installing the board, clean all the components in contact with the heatsink and the corresponding surfaces of the heat sink. Re-coat the cleaned areas with Jermyn Thermaflow A30. To re-install the board reverse the removal procedure taking particular care with the following: •...

  • Page 91: Replacement Of Escutcheon Or Switch Substrate

    12. Test the switch operation as described in paragraph 6.2.3. 13. Refill the slot through which the connections pass with Expandite Silicone Sealant 88 (Codan Pt No. 71-30000-007). Ensure that the slot is completely sealed but that no excess sealant remains around the slot, particularly on the front face.
  • Page 92 6-14 Maintenance 8525B/8528 Technical Service Manual 15. Peel off the backing sheet from the front face of the switch substrate and place the escutcheon over the substrate. When the escutcheon is correctly positioned press firmly all over its face to ensure its adhesion to the substrate.

  • Page 93: Adjustments

    8525B/8528 Technical Service Manual Adjustments 7.1 Introduction Two types of adjustment are covered under separate headings. • Channel Addition: change EPROM (no internal adjustments necessary) • Preset Adjustments: normally factory-set adjustments will require attention only if components which affect their settings are replaced. 7.2 Channel Addition (EPROM Replacement) The EPROM is mounted in a socket on the Microprocessor Controller PCB and may be changed as follows:...

  • Page 94: Channel Addition, Programming P Channels (8528)

    7-2 Adjustments 8525B/8528 Technical Service Manual 7.2.1 Channel Addition, Programming P Channels (8528) In 8528 series transceivers, ninety-nine ‘P’ channels can be programmed from the front panel to suit the user’s requirements. However, to prevent transmission on frequencies for which the operator is not authorised, option TxD inhibits the entry of new transmit frequencies by the operator.
  • Page 95 8525B/8528 Technical Service Manual Adjustments 7-3 Transmit Frequency Programming Once the link is effective, transmit frequencies can be entered from the front panel as follows: Action Display will show Remarks Select any channel Tx and Rx frequencies Channel No. Press Enter Tx____ Next action must be started within 60...
  • Page 96 7-4 Adjustments 8525B/8528 Technical Service Manual Used Indication Channel numbers will normally be accepted on pressing the Enter pad. However, if a channel with the entered number has previously been programmed and the over-write link is not installed, the display will show USEd.

  • Page 97: Preset Adjustments

    Multimeter or meters for measuring voltages (20kΩ/V or better) and current (l00mA and 1A ranges) and an audio voltmeter. • Transceiver Test Unit to Codan drawing 04-01868. (The isolating transformer should be screened to prevent pick-up from nearby mains transformers.) •...

  • Page 98: Voltage Regulators

    7-6 Adjustments 8525B/8528 Technical Service Manual 7.3.2 Voltage Regulators None of the voltage regulators used are adjustable, so only their output voltage can be checked. The location and correct output voltages are as follows: 1. B rail regulator, 10V ±0.2V; IC1 on Motherboard. 2.

  • Page 99: 45Mhz If Alignment-Receive

    8525B/8528 Technical Service Manual Adjustments 7-7 7.3.5 45MHz IF Alignment—Receive 1. Ensure the dual coax socket is connected to the PA and Filter PCB. 2. Connect the signal generator to the antenna socket. 3. Select a channel (USB) and adjust the signal generator output to the selected channel frequency plus 1kHz.
  • Page 100 7-8 Adjustments 8525B/8528 Technical Service Manual 7. Adjust L29 and C64 (second and fourth holes from left-transceiver facing toward operator) for maximum amplitude of the displayed waveform. 8. Set the transceiver to receive and repeat steps (1) to (5) of 7.3.5. 9.

  • Page 101: Highpass Filters

    8525B/8528 Technical Service Manual Adjustments 7-9 7.3.8 Highpass Filters Five adjustments are required for the highpass filters, one for the Broadcast filter on the PA and Filter PCB and one each for the band selected filters on the RF, Mixer, and Dual Synthesizer PCB. To adjust these filters: 1.

  • Page 102: Noise Limiter

    7-10 Adjustments 8525B/8528 Technical Service Manual 7.3.9 Noise Limiter 1. Connect a DC Voltmeter to TP6 on the RF, Mixer, and Dual Synthesizer PCB. With no signal applied TP6 should be at approximately 2.5V DC. 2. Connect a signal generator to the antenna socket, select a channel (USB) and set the signal generator output to the selected channel frequency plus 1kHz.

  • Page 103: Mute Adjustments

    8525B/8528 Technical Service Manual Adjustments 7-11 8528S If the transceiver is fitted for LSB operation: 1. Select a channel with LSB mode enabled. 2. Connect the frequency counter, via a high impedance (x10) probe, to the inner conductor of the Local Oscillator cable on the RF Mixer and Dual Synthesizer PCB.

  • Page 104: Output Power

    7-12 Adjustments 8525B/8528 Technical Service Manual 7.3.14 Output Power 1. Ensure the dual coax socket is connected to the PA and filter PCB. 2. Connect an RMS or PEP power meter with dummy load to the antenna socket. 3. Connect a CRO via a 47kΩ resistor to the antenna socket. 4.

  • Page 105: Options Sd, Sde And Sdem

    8525B/8528 Technical Service Manual Adjustments 7-13 7.3.15 Options SD, SDE and SDEM With these options fitted the oscillator frequency of the phase locked loop on the Selective Call PCB must be set up as follows: 1. Apply a 1775Hz sine wave at 1.0Vpp to pin 2 of J1 on the Selective Call PCB.

  • Page 106: Selective Call Code Settings (8525B)

    7-14 Adjustments 8525B/8528 Technical Service Manual 7.3.17 Selective Call Code Setting (8525B) When any of the selective calling options are fitted, identity code switches within the unit (refer to Figure 7.2) must be set. With Options SE2 or SDE, both the self ident and the called address (i.e. the identification of the station it is intended to call) are set entirely on the internal switches.

  • Page 107: Message Length Setting

    8525B/8528 Technical Service Manual Adjustments 7-15 4. Set the called address switches: • With Options SE2 or SDE fitted—set all the switches in the group to the digits of the identification number of the station to be called. • With Options SDEM or SM fitted—set any of the switches in the group which are not duplicated on the panel.

  • Page 108: Receiver Performance Checks

    7-16 Adjustments 8525B/8528 Technical Service Manual 7.4 Receiver Performance Checks 7.4.1 Sensitivity and Signal + Noise to Noise Ratio Connect an AC voltmeter across the audio output. Set the signal generator to 0.35µV PD output, connect it to the antenna socket and adjust the frequency to produce a 1kHz audio output.

  • Page 109: Transmitter Performance Checks

    8525B/8528 Technical Service Manual Adjustments 7-17 With the signal generator output set to produce a 1kHz audio output at a 0.5µV PD level switch the noise limiter on and off by shorting TP6 on the RF Mixer and Dual Synthesizer PCB. When ON, the audio tone should be clearly heard if the noise limiter is effective.

  • Page 110: Emergency Call Frequencies

    7-18 Adjustments 8525B/8528 Technical Service Manual 7.6 Emergency Call Frequencies 8525B/8528 RFDS Select an RFDS channel and disconnect dual coax socket to PA and Filter PCB. Press the Emgcy Call pad and measure the frequencies on pins 10 and 13 of IC12 on the Microprocessor Controller PCB. Frequencies should be 880Hz ±2Hz and 1320Hz ±2Hz respectively.

  • Page 111: Parts List

    • manufacturer and manufacturer’s part number. • Codan part number. Note: Items having numerical references identifying specific components or subassemblies may be encountered in the parts lists included in this handbook. These items, selected from master manufacturing...

  • Page 112: Component Substitution

    8-2 Parts List 8525B/8528 Technical Service Manual 8.1.2 Component Substitution Due to continuous process of updating equipment and changes in component availability, minor variations in components may be noted from those listed. Equipment performance is in no way adversely affected by their substitution.

  • Page 113: Parts List

    8525B/8528 Technical Service Manual Parts List 8-3 8.2 Parts List 8.2.1 Transceiver Sundry Parts 08-03786-100 Includes Control Head Parts 8.2.2 RF Mixer and Dual Synthesizer 03740-001 Includes: 45MHz IF PCB 08-03097 VCO1 PCB 08-03098 VCO2 PCB 08-03099 8.2.3 Audio and IF 1650kHz PCB 08-03025 8.2.4 Microprocessor Controller...
  • Page 114 8-4 Parts List 8525B/8528 Technical Service Manual 8.2.16 Cover and Fan Assembly 08-03690 Includes: Fan Controller 08-03334 8.2.17 Antenna Driver PCB 08-04285-001 8.2.18 Cable Interface (Transceiver/Head) 08-03051 8.2.19 Data Mode Switch PCB 08-05041-001 8.2.20 Microprocessor Controller (RS232) 08-05090-001 Includes: Microprocessor Interface 08-05088 Microprocessor Assembly 08-05089...
  • Page 115 8525B/8528 Technical Service Manual Drawings Drawings Transceiver Layout 16-00035-004 Control Head Layout, 8530 16-00035-003 Control Head Layout, 8531 16-00035-005 RF Mixer and Dual Synthesizer Circuit Diagram 04-02450 PCB Assembly 08-03740 45MHz IF PCB Assembly 08-03097 VCO1 and Mixer PCB Assembly 08-03098 VCO2 and Mixer PCB Assembly...
  • Page 116 9-2 Drawings 8525B/8528 Technical Service Manual PA & Exciter Interface Circuit Diagram 04-02434 PCB Assembly 08-03691 Selective Call Circuit Diagram 04-02250 SD/SDE/SDEM Selective Call PCB Assembly 08-03300 Two-tone Decoder Circuit Diagram 04-02231 PCB Assembly 08-03273 Fan Controller Circuit Diagram 04-02260 PCB Assembly 08-03334 Antenna Driver...

This manual is also suitable for:

8528 series

Table of Contents