TB8100 Service Manual TB8000/TB8100_Service_Manual/TB8100_Service_Manual
TB8000/TB8100_Service_Manual/TB8100_Service_Manual TB8100_Service_Manual
TB8000/TB8100_Service_Manual/TB8100_Service_Manual TB8100_Service_Manual
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TB8100 base station Service Manual MB8100-00-00-812 Issue 1 April 2004 Tait Contact Information Tait Radio Communications http:// www.taitworld.com Corporate Head Office New Zealand Tait North Asia Tait Electronics Ltd P.O. Box 1645 Christchurch New Zealand E-mail: info@taitworld.com Website: http://www.taitworld.com Technical Support: E-mail: support@taitworld.com Website: http://support.taitworld.com Tait North America Regional Head Office - United States of America Tait North America Inc. E-mail: usa@taitworld.com Regional Head Office - Hong Kong Tait Mobile Radio (Hong Kong) Ltd E-mail: hongkong@taitworld.com Beijing Tait Mobile Radio (Hong Kong) Ltd E-mail: beijing@taitworld.com Tait South Asia Regional Head Office - Singapore Tait Electronics (Far East) Pte Ltd E-mail: singapore@taitworld.com Thailand Tait Mobile Radio Ltd E-mail: thailand@taitworld.com Canada Tait North America Inc. E-mail: canada@taitworld.com Oceania Latin America Australia Tait Electronics (Aust) Pty Ltd E-mail: australia@taitworld.com Tait Latin America E-mail: latinamerica@taitworld.com Tait Europe Regional Head Office - United Kingdom Tait Mobile Radio Ltd E-mail: teusales@tait.co.uk 2 New Zealand Tait Communications Ltd E-mail: headoffice@tcl.tait.co.nz Note: For the addresses and phone numbers of the above regional offices refer to the TaitWorld website. TB8100 Service Manual © Tait Electronics Ltd April 2004 Contents Tait Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Scope of Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Enquiries and Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Updates of Manual and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Copyright. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Associated Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Typographical Conventions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Publication Record. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1 Safety and Servicing Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.1 Personal Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Lethal Voltages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Explosive Environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Beryllium Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Proximity to RF Transmissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 High Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.2 Equipment Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 ESD Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Aerial Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.3 Identifying Screw Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Torx Recess Head Screws. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Allen Recess Head UNC Screws. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Pozidriv Recess Head Screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.4 Recommended Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1.5 Replacing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Surface Mount Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Leaded Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Cased Mica Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 1.6 Regulatory Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 1.7 PCB Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2 Reciter Circuit Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.1 Digital Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Digital IF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Digital Signal Processor (DSP). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Reduced Instruction Set Computer (RISC). . . . . . . . . . . . . . . . . . . . . 25 40MHz Digital Clock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.2 Reference Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Synthesizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 VCXO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 TB8100 Service Manual © Tait Electronics Ltd April 2004 3 Reference Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.3 Receiver RF Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Front End . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mixer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IF Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AGC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 31 31 33 33 34 34 2.4 Exciter RF Circuitry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frequency Control Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exciter Control Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 35 38 38 39 2.5 System Interface PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.6 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3 Reciter Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.1 Disassembly and Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Identifying the Reciter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Screw Torque Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Removing the Covers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Removing the Front and Rear Panels . . . . . . . . . . . . . . . . . . . . . . . . . Refitting the Front and Rear Panels . . . . . . . . . . . . . . . . . . . . . . . . . . Refitting the Covers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 52 54 54 54 55 56 3.2 Replacing the Digital PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.3 Replacing the System Interface PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.4 Replacing the RF PCB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4 4 Power Amplifier Circuit Description . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.1 Microprocessor Control Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diagnostics and Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PA-Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Foldback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fan Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Temperature Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ambient Air Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 68 69 69 71 71 71 72 72 72 73 4.2 RF Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6W PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60W PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low Pass Filter and Directional Coupler PCB . . . . . . . . . . . . . . . . . . . Splitter and Combiner PCBs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interconnect PCBs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 73 73 74 74 74 TB8100 Service Manual © Tait Electronics Ltd April 2004 5 Power Amplifier Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.1 Disassembly and Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Identifying the PA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Screw Torque Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Removing the Airflow Duct and Cover . . . . . . . . . . . . . . . . . . . . . . . 80 Removing the Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Refitting the Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Refitting the Cover and Airflow Duct. . . . . . . . . . . . . . . . . . . . . . . . . 82 5.2 PCB Connecting Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 5.3 Replacing the 6W PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 5.4 Replacing the 60W PCB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 5.5 Replacing the 60W RF Power Transistor . . . . . . . . . . . . . . . . . . . . . . . . 87 5.6 Replacing the Control PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 5.7 Replacing the Low Pass Filter/Directional Coupler PCB . . . . . . . . . . . . . 91 5.8 Replacing the Interconnect PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 5.9 Replacing the Splitter/Combiner PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . 93 6 Power Management Unit Circuit Description . . . . . . . . . . . . . . . . . . . 99 6.1 Microprocessor Control Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 6.2 AC Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 6.3 DC Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7 Power Management Unit Servicing . . . . . . . . . . . . . . . . . . . . . . . . . .113 7.1 Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Personal Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Equipment Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Replacing Components Connected To The Mains . . . . . . . . . . . . . . 114 7.2 Disassembly and Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Mechanical Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Identifying the PMU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 Screw Torque Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 Removing the Top and Bottom Covers . . . . . . . . . . . . . . . . . . . . . . 118 Removing the Front and Rear Panels . . . . . . . . . . . . . . . . . . . . . . . . 118 Disconnecting the AC and DC Modules . . . . . . . . . . . . . . . . . . . . . . 119 Reconnecting the AC and DC Modules . . . . . . . . . . . . . . . . . . . . . . 119 Refitting the Front and Rear Panels . . . . . . . . . . . . . . . . . . . . . . . . . 122 Refitting the Top and Bottom Covers. . . . . . . . . . . . . . . . . . . . . . . . 122 7.3 Replacing the Plug-in Cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 7.4 Replacing the Auxiliary Power Supply PCB. . . . . . . . . . . . . . . . . . . . . . 126 8 Control Panel Circuit Description . . . . . . . . . . . . . . . . . . . . . . . . . . .131 8.1 Control Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 8.2 Audio Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 8.3 Power Save. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 TB8100 Service Manual © Tait Electronics Ltd April 2004 5 8.4 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 9 Control Panel Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135 9.1 Identifying the Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 9.2 Screw Torque Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 9.3 Replacing the PCB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 9.4 Replacing the Speaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 10 Subrack Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149 6 TB8100 Service Manual © Tait Electronics Ltd April 2004 List of Illustrations Figure 1.1 Figure 1.2 Figure 1.3 Figure 2.1 Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5 Figure 2.6 Figure 2.7 Figure 2.8 Figure 2.9 Figure 2.10 Figure 2.11 Figure 2.12 Figure 3.1 Figure 3.2 Figure 3.3 Figure 3.4 Figure 3.5 Figure 3.6 Figure 4.1 Figure 4.2 Figure 4.3 Figure 5.1 Figure 5.2 Figure 5.3 Figure 5.4 Figure 5.5 Figure 5.6 Figure 5.7 Figure 5.8 Figure 5.9 Figure 5.10 Figure 5.11 Figure 6.1 Figure 6.2 Figure 6.3 Figure 6.4 Figure 6.5 Figure 6.6 Figure 7.1 Figure 7.2 Figure 7.3 Figure 7.4 Figure 7.5 Figure 7.6 Typical Antistatic Bench Set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Identifying Torx Screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Identifying Pozidriv and Philips Screws and Screwdrivers . . . . . . . . . . . . 17 Reciter High Level Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Reciter Digital Circuitry Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . 24 Reciter RISC Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . 27 Reciter External Reference Block Diagram . . . . . . . . . . . . . . . . . . . . . . 29 Reciter Receiver RF Circuitry Block Diagram. . . . . . . . . . . . . . . . . . . . 31 Reciter Receiver Synthesizer Block Diagram . . . . . . . . . . . . . . . . . . . . . 32 Comparison of VCXO and VCO Modulation Responses . . . . . . . . . . . . 36 Reciter Exciter Synthesizer Modulator Block Diagram . . . . . . . . . . . . . . 37 Reciter System Interface PCB Block Diagram . . . . . . . . . . . . . . . . . . . . 41 Reciter Power Supply Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Identifying the Circuitry on the Digital and System Interface PCBs . . . . . 47 Identifying the Circuitry on the RF PCB . . . . . . . . . . . . . . . . . . . . . . . . 49 Identifying the Reciter PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Removing the Front and Rear Panels. . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Replacing the Digital and System Interface PCBs . . . . . . . . . . . . . . . . . . 57 Reconnecting the Flexible Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . 58 Replacing the RF PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Reciter Mechanical Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 PA High Level Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 PA Control, RF and Power Supply Circuitry Block Diagram . . . . . . . . . 70 Identifying the Circuitry on the PA PCBs . . . . . . . . . . . . . . . . . . . . . . . 75 Identifying the PA PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Removing the Airflow Duct, Cover and Front Panel . . . . . . . . . . . . . . . 81 PCB Connecting Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Replacing the 6W PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Replacing the 60W PCB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Replacing the 60W RF Power Transistor . . . . . . . . . . . . . . . . . . . . . . . 88 Replacing the Control PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Replacing the LPF/Directional Coupler PCB. . . . . . . . . . . . . . . . . . . . . 92 Replacing the Splitter/Combiner PCBs . . . . . . . . . . . . . . . . . . . . . . . . . 94 PA Mechanical Assembly - Sheet 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 PA Mechanical Assembly - Sheet 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 PMU High Level Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 PMU Microprocessor Functional Block Diagram . . . . . . . . . . . . . . . . . 102 PMU AC Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 PMU DC Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Identifying the Circuitry on the AC Module PCBs . . . . . . . . . . . . . . . . 109 Identifying the Circuitry on the DC Module PCBs. . . . . . . . . . . . . . . . 111 Identifying the PMU PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Disconnecting the AC and DC Modules . . . . . . . . . . . . . . . . . . . . . . . 120 Reconnecting the AC and DC Modules. . . . . . . . . . . . . . . . . . . . . . . . 121 Replacing the Plug-in Cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 Replacing the Auxiliary Power Supply PCB. . . . . . . . . . . . . . . . . . . . . 126 PMU Mechanical Assembly - Sheet 1 . . . . . . . . . . . . . . . . . . . . . . . . . 129 TB8100 Service Manual © Tait Electronics Ltd April 2004 7 Figure 7.7 Figure 8.1 Figure 9.1 Figure 9.2 Figure 9.3 Figure 9.4 Figure 10.1 Figure 10.2 Figure 10.3 8 PMU Mechanical Assembly - Sheet 2 . . . . . . . . . . . . . . . . . . . . . . . . . . Control Panel High Level Block Diagrams. . . . . . . . . . . . . . . . . . . . . . . Replacing the Control Panel PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reconnecting the Flexible Connector . . . . . . . . . . . . . . . . . . . . . . . . . . Replacing the Speaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Control Panel Mechanical Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . Front Panel Mechanical Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subrack Mechanical Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cable Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 132 137 138 139 141 145 146 147 TB8100 Service Manual © Tait Electronics Ltd April 2004 Preface Scope of Manual This manual contains information on servicing TB8100 base station system equipment. It also provides circuit descriptions and mechanical assembly drawings for each module. Enquiries and Comments If you have any enquiries regarding this manual, or any comments, suggestions and notifications of errors, please contact Technical Support (refer to “Tait Contact Information” on page 2). Updates of Manual and Equipment In the interests of improving the performance, reliability or servicing of the equipment, Tait Electronics Ltd reserves the right to update the equipment or this manual or both without prior notice. Copyright All information contained in this manual is the property of Tait Electronics Ltd. All rights are reserved. This manual may not, in whole or in part, be copied, photocopied, reproduced, translated, stored, or reduced to any electronic medium or machine-readable form, without prior written permission from Tait Electronics Ltd. All trade names referenced are the service mark, trademark or registered trademark of the respective manufacturers. Disclaimer There are no warranties extended or granted by this manual. Tait Electronics Ltd accepts no responsibility for damage arising from use of the information contained in the manual or of the equipment and software it describes. It is the responsibility of the user to ensure that use of such information, equipment and software complies with the laws, rules and regulations of the applicable jurisdictions. TB8100 Service Manual © Tait Electronics Ltd April 2004 9 Associated Documentation TB8100 Installation and Operation Manual. TB8100 Installation Guide (a subset of the Installation and Operation Manual.). TB8100 Specifications Manual. TB8100 Service Kit and Alarm Center User’s Manuals and online Help. TB8100 Calibration Kit User’s Manual and online Help. Technical notes are published from time to time to describe applications for Tait products, to provide technical details not included in manuals, and to offer solutions for any problems that arise. All available TB8100 product documentation is provided on the CD supplied with the base station1. Updates may also be published on the Tait support website. Typographical Conventions Within this manual, four types of alerts are given to the reader: Warning, Caution, Important and Note. The following paragraphs illustrate each type of alert and its associated symbol. Warning!! This alert is used when there is a potential risk of death or serious injury. Caution This alert is used when there is a risk of minor or moderate injury to people. Important This alert is used to warn about the risk of equipment damage or malfunction. Note This alert is used to highlight information that is required to ensure procedures are performed correctly. 1. Technical notes are only available in PDF format from the Tait support website. Consult your nearest Tait Dealer or Customer Service Organisation for more information. 10 TB8100 Service Manual © Tait Electronics Ltd April 2004 Publication Record Issue 1 TB8100 Service Manual © Tait Electronics Ltd April 2004 Publication Date April 2004 Description first release 11 12 TB8100 Service Manual © Tait Electronics Ltd April 2004 1 Safety and Servicing Information This chapter contains general information on safety and servicing procedures for the TB8100 base station system (BSS) modules: ■ reciter ■ power amplifier (PA) ■ power management unit (PMU) ■ control panel. You will find specific safety and servicing information about individual modules and procedures in the appropriate chapters. 1.1 Personal Safety Lethal Voltages Warning!! The PMU contains voltages that may be lethal. Refer to the ratings label on the rear of the module. The TB8100 BSS must be installed so that the rear of the PMU is located in a service access area. Disconnect the mains IEC connector and wait for five minutes for the internal voltages to self-discharge before dismantling. The AC power on/off switch does not isolate the PMU from the mains. It breaks only the phase circuit, not the neutral. The PMU should be serviced only by qualified technicians. All servicing should be carried out only when the PMU is powered through a mains isolating transformer of sufficient rating. We strongly recommend that the mains power to the whole of the repair and test area is supplied via an earth leakage circuit breaker. Explosive Environments Warning!! TB8100 Service Manual © Tait Electronics Ltd April 2004 Do not operate TB8100 BSS equipment near electrical blasting caps or in an explosive atmosphere. Operating the equipment in these environments is a definite safety hazard. Safety and Servicing Information 13 Beryllium Oxide Caution The termination resistors used in the 100W power amplifier contain some beryllium oxide. This substance is perfectly harmless in its normal solid form, but can become a severe health hazard when it has been reduced to dust. For this reason the termination resistors should not be broken open, mutilated, filed, machined, or physically damaged in any way that can produce dust particles. You should safely dispose of all used or obsolete components according to your local regulations. Proximity to RF Transmissions Do not operate the transmitter when someone is standing within 90cm (3ft) of the antenna. Do not operate the transmitter unless you have checked that all RF connectors are secure. High Temperatures Take care when handling a PMU or PA which has been operating recently. Under extreme operating conditions (+60°C [+140°F] ambient air temperature) or high duty cycles the external surfaces of the PMU and PA can reach temperatures of up to +80°C (+176°F). 14 Caution The magnetics and power devices attached to the heatsink in the PMU get hot when they are operating. Take care when working on a PMU that has been in recent use. Caution Touching high-power RF components or circuits can cause serious burns. We strongly recommend you do not touch any RF components or tracks in the PA while it is transmitting. Safety and Servicing Information TB8100 Service Manual © Tait Electronics Ltd April 2004 1.2 Equipment Safety ESD Precautions Important This equipment contains devices which are susceptible to damage from static charges. You must handle these devices carefully and according to the procedures described in the manufacturers’ data books. We recommend you purchase an antistatic bench kit from a reputable manufacturer and install and test it according to the manufacturer’s instructions. Figure 1.1 shows a typical antistatic bench set-up. You can obtain further information on antistatic precautions and the dangers of electrostatic discharge (ESD) from standards such as ANSI/ESD S20.20-1999 or BS EN 100015-4 1994. Figure 1.1 Typical Antistatic Bench Set-up conductive wrist strap dissipative rubber bench mat common point ground (building ground or mains ground via 1M ohm series resistor) Aerial Load The TB8100 BSS equipment has been designed to operate safely under a wide range of aerial loading conditions. However, we strongly recommend that the transmitter should always be operated with a suitable load to prevent damage to the transmitter output power stage. TB8100 Service Manual © Tait Electronics Ltd April 2004 Safety and Servicing Information 15 1.3 Identifying Screw Types Torx Recess Head Screws Torx recess head screws are the standard type of screw used in all TB8100 equipment, although Pozidriv and Allen recess head screws are also used in a few special applications. Figure 1.2 below shows a typical Torx recess head screw (actual hardware may differ slightly from this illustration due to variations in manufacturing techniques). Figure 1.2 Identifying Torx Screws “star” shaped recess with six internal notches Allen Recess Head UNC Screws Allen recess head 4-40 UNC thread screws are used to secure the RF power transistors in the TB8100 power amplifier and cannot be interchanged with M3 screws (refer to Figure 5.10 on page 97). Pozidriv Recess Head Screws Pozidriv recess head screws are used in TB8100 equipment in a few special applications. It is important that you use the correct type and size screwdriver to avoid damaging the screw head. It is particularly important that you do not use Philips screwdrivers on Pozidriv screw heads as the tapered driving flutes of the Philips screwdriver do not engage correctly with the parallel-sided slots in the Pozidriv screw head. This can result in considerable damage to the screw head if the screwdriver tip turns inside the recess. 16 Safety and Servicing Information TB8100 Service Manual © Tait Electronics Ltd April 2004 Note If you find you need excessive downwards pressure to keep the screwdriver tip in the Pozidriv screw head, you are probably using the wrong type or size screwdriver. Figure 1.3 below shows the main differences between typical Pozidriv and Philips screw heads and screwdriver tips (actual hardware may differ slightly from these illustrations due to variations in manufacturing techniques). Figure 1.3 Identifying Pozidriv and Philips Screws and Screwdrivers Pozidriv Philips internal notches no special markings “star” markings between slots slots with parallel sides slots with tapered sides driving flutes with parallel sides driving flutes with tapered sides ridges between driving flutes TB8100 Service Manual © Tait Electronics Ltd April 2004 Safety and Servicing Information 17 1.4 Recommended Tools It is beyond the scope of this manual to list every tool that a service technician should carry. However, the tools specifically required for servicing TB8100 BSS equipment are listed in the table below. You can also obtain the TBA0ST2 tool kit from your nearest Tait Dealer or Customer Service Organisation. It contains the basic tools needed to install, tune and service TB8100 BSS equipment. Driver/ Spanner Size Location / Function Torx T8a M2.5 securing the SMA connector to the reciter and PA front panel Torx T10a M3 all M3 screws Torx T20a M4 all M4 screws Pozidriv PZ3 M6 DC input terminals on the PMU 3/32in Allen key 4-40 UNC securing the RF power transistors to the PA heatsink 5.5mm AFa M3 securing the speaker to the control panel chassis 11mm AF securing the BNC/TNC connectors to the reciter rear panel a. Included in the TBA0ST2 tool kit. 1.5 Replacing Components Ensure that any replacement components are of the same type and specifications as the originals. This will prevent the performance and safety of the TB8100 equipment from being degraded. Surface Mount Devices Important 18 Safety and Servicing Information Surface mount devices (SMDs) require special storage, handling, removal and replacement techniques. This equipment should be serviced only by an approved Tait Dealer or Customer Service Organisation equipped with the necessary facilities. Repairs attempted with incorrect equipment or by untrained personnel may result in permanent damage. If in doubt, contact your nearest Tait Dealer or Customer Service Organisation. TB8100 Service Manual © Tait Electronics Ltd April 2004 Leaded Components Whenever you are doing any work on the PCB that involves removing or fitting components, you must take care not to damage the copper tracks or pads. The two satisfactory methods of removing components from platedthrough hole (PTH) PCBs are detailed below. Desoldering Iron Method This method requires the use of a desoldering station. 1. Place the tip over the lead and, as the solder starts to melt, move the tip in a circular motion. 2. Start the suction and continue the movement until three or four circles have been completed. 3. Remove the tip while continuing suction to ensure that all solder is removed from the joint, then stop the suction. 4. Before pulling the lead out, ensure it is not stuck to the plating. 5. If the lead is still not free, resolder the joint and try again. Note Component Cutting Method The desoldering iron does not usually have enough heat to desolder leads from the ground plane. Additional heat may be applied by holding a soldering iron on the tip of the desoldering iron (this may require some additional help). 1. Cut the leads on the component side of the PCB. 2. Heat the solder joint sufficiently to allow easy removal of the lead by drawing it out from the component side: do not use undue force. 3. Fill the hole with solder and then clear with solderwick. Cased Mica Capacitors Cased mica capacitors can be removed by heating the top with a heavy-duty soldering iron and gently lifting the capacitor off the PCB with a solder-resistant spike or equivalent. Make sure that the solder at the tab solder joint is melted or removed before attempting to lift the capacitor. 1.6 Regulatory Information Any modifications you make to this equipment which are not authorised by Tait Electronics Ltd may invalidate your compliance authority’s approval to operate the equipment. TB8100 Service Manual © Tait Electronics Ltd April 2004 Safety and Servicing Information 19 1.7 PCB Information All PCBs are identified by a unique 10 digit IPN (internal part number) which is printed onto the PCB (usually on the top side), as shown in the example below. The last two digits of this number define the issue status, which starts at 01 and increments through 02, 03, 04 etc. as the PCB is updated. Information on individual PCBs is published in PCB Information Packages. This information consists of: ■ parts lists ■ grid reference indexes ■ PCB layouts ■ schematics (circuit diagrams). Contact your nearest Customer Service Organisation for more details on the availability of PCB Information Packages (refer to “Tait Contact Information” on page 2). 20 Safety and Servicing Information TB8100 Service Manual © Tait Electronics Ltd April 2004 2 Reciter Circuit Description The reciter comprises three PCBs: an RF, a digital, and an optional system interface PCB. These PCBs are mounted on a central chassis/heatsink. Figure 2.1 below shows the configuration of the main circuit blocks, and the main inputs and outputs for power, RF and control signals. The locations of the main circuit blocks on the PCBs are shown in Figure 2.11 on page 47 and Figure 2.12 on page 49. Figure 2.1 Reciter High Level Block Diagram 28VDC I/P 28V Power Supply 28V Power Supply 5V 3.3V 9.3V IF RF I/P Receiver Digital Receiver CODECs External Reference Frequency (if used) Reference 12.8MHz Ref. Frequency Subsystem DSP/RISC 40MHz Clock CODEC Audio & RSSI System Interface PCB Digital Receiver CODEC DSP Synthesizer Subsystem RF O/P + PA Key Exciter Control & Communications Modulation & Frequency Control RISC Control & Communications CODEC Audio RF PCB Digital PCB System Control Bus TB8100 Service Manual © Tait Electronics Ltd April 2004 Control & Communications System I/O Reciter Circuit Description 21 2.1 Digital Circuitry Refer to Figure 2.2 on page 24. Digital IF The heart of the digital IF system is the 14-bit analogue-to-digital converter (ADC). This is a high-speed device, with a multi-staged “pipeline” architecture, which is clocked and outputs samples at 40MSPS (megasamples per second). The analogue IF input of the ADC is a differential structure, and the output is via a 14-bit parallel bus. The band-limited 70.1MHz IF signal is sub-sampled by the ADC at 40MSPS. The sub-sampling results in images of the input signal appearing at other frequencies so that the ADC behaves in a similar fashion to a mixer. The digital output therefore contains information in the form of images, which can be digitally processed to extract one of the many signals. The lowest frequency image for the 70.1MHz IF and 40MHz clock is at 9.9MHz. The digital downconverter (DDC) digitally downconverts the desired image (9.9MHz) to baseband. This is achieved by digital mixing with a numerically controlled oscillator (NCO). The mixing process is done using in-phase and quadrature methods to achieve image rejection, and allows channel filtering to be applied before the signal is passed to the digital signal processor (DSP) for demodulation. The digital channel filtering also decimates the sample rate down to 50kSPS (kilosamples per second) for the DSP. Digital Signal Processor (DSP) The DSP is responsible for software processing of digitised signals in the receiver and transmitter. The processing word width is 16-bit fixed point. There are 96 kilobytes of on-chip program memory, and 64 kilobytes of on-chip data memory. Although no external memory is used, the external memory interface is connected to the DDC for initialisation and configuration. Transmit Functions 22 The DSP performs the following transmit functions: ■ CTCSS and DCS sub-audible signal generation ■ CWID generation ■ pip tone generation ■ audio filtering: including removal of sub-audible components, preemphasis and low pass filtering ■ signal path switching ■ signal level adjustment Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 Receive Functions ■ peak FM deviation limiting ■ FM signal generation by controlling the dual point modulator ■ calibration parameter estimation ■ line level monitoring. The DSP performs the following receive functions: ■ detection of CTCSS and DCS signalling ■ audio filtering: including removal of sub-audible components, deemphasis and low pass filtering ■ signal path switching ■ signal level adjustment ■ FM demodulation of the base band signal ■ RSSI measurement for monitoring and RSSI signal voltage output ■ SINAD measurement ■ measurement and detection for control of the audio mute ■ calibration parameter estimation ■ line level monitoring. Serial Ports The DSP has three synchronous serial ports. Serial port 1 is connected to the DDC and receives base band samples. Serial port 2 is connected to the three CODECs (encoder/decoder). Serial port 3 is not used. CODECs The three CODECs provide the audio frequency analogue interface to the reciter. There are six analogue input and six analogue output paths. The sample rate on all paths is 25kSPS and the sampling resolution is 16 bits. The CODEC inputs are as follows: ■ two input signals from the frequency control loop (FCL) ■ balanced line input ■ unbalanced line input ■ microphone input ■ synthesizer loop control voltage. The CODEC outputs are as follows: ■ VCO voltage control line ■ VCXO voltage control line ■ balanced line output ■ unbalanced line output ■ speaker output ■ RSSI voltage indicator. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 23 70.1MHz IF from RF PCB 24 Reciter Circuit Description Digital PCB 40MHz Clock ADC Digital IF DDC 40MHz Clock 40MSPS DSP Loopback Crosspoint Switch RSSI Process FM Demodulation Tx Audio Processor Noise Mute Rx Audio Processor Tx Crosspoint Switch DSP Frequency Control Loop Section Signalling Processor Rx Crosspoint Switch Interface (RISC/ DSP) Audio & DC Measurement Interface (serial port) CODECs & Signal Conditioning serial port CODECs & Signal Conditioning serial port serial port Interface (RISC/ DSP) RISC CODECs & Signal Conditioning serial port Digital Signal Paths FCL Q FCL I VCO Control Feedback VCXO Modulation VCO Modulation RF Frequency Control Loop Section Tx VCXO Tx VCO Balanced Audio Input Unbalanced Audio Input Discrete I/O & SIO Bus RF PCB Tx Synthesiser System Interface PCB RSSI Balanced Audio Output Unbalanced Audio Output LEDs and Switches Programming Port Microphone Speaker Control Panel PCB Figure 2.2 Reciter Digital Circuitry Block Diagram TB8100 Service Manual © Tait Electronics Ltd April 2004 Reduced Instruction Set Computer (RISC) Refer to Figure 2.3 on page 27. Hardware and I/O The RISC processor engine is a Samsung S3C3410X processor with a 40MHz external clock. It has 4 megabytes of flash memory containing the following: ■ bootloader ■ application code ■ DSP code ■ non-volatile data ■ 2 megabytes of RAM for run-time variables. The discrete digital inputs and outputs are as follows: ■ chip select signals to synthesizers ■ out-of-lock signals from synthesizers ■ external reference detection ■ internal/external reference selection ■ Rx Gate output ■ Tx Relay output ■ reciter hex switch ■ reciter alarm LED ■ DIP switch for manufacturing testing ■ debug LEDs ■ fan good input ■ flash programming voltage control. The RISC has the following serial interfaces: ■ asynchronous serial port for communication with the Service Kit software and CCTM ■ serial peripheral interface (SPI) for programming the synthesizers ■ SPI for communication with the system interface PCB ■ Responsibilities I2C for communication with the control panel and other modules in the subrack. The RISC communicates with the DSP’s shared memory via a host port interface. It loads the DSP code and monitors and controls the following DSP operations: ■ receive path ■ transmit path ■ crosspoint switches ■ power supplies ■ PA Key output. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 25 The RISC controls the frequency generation subsystem. It detects an external reference source and selects internal or external reference. It also programs, and handles out-of-lock signals for, the following synthesizers: ■ 12.8MHz external reference synthesizer ■ 40MHz digital clock synthesizer ■ receiver synthesizer ■ exciter synthesizer. The RISC communicates with the control panel via I2C bus to: ■ read the button states ■ read the microphone PTT state ■ control the LEDs ■ turn the speaker amplifier on and off ■ turn the microphone amplifier on and off. The following signals go via the control panel for signal conditioning: ■ Service Kit communication via the RS-232 interface ■ fan-good indication (front panel fans). Note that the volume control on the control panel is analogue only and is not controlled by the RISC. The RISC communicates with the other modules in the subrack via I2C in order to: ■ verify that they are present ■ write configuration settings ■ read their current status. The RISC subsystem communicates with the system interface PCB via SPI to: ■ set input and output gains ■ mute and unmute outputs ■ read digital inputs ■ write digital outputs. The Rx Gate and Tx Relay lines go via the system interface PCB for signal conditioning. 26 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 2.3 Reciter Status Reciter RISC Functional Block Diagram Alarm LEDs Hex Switch 2 IC System Control Bus UART Fan Good System Control Bus to BSS Modules & Control Panel Flash Programming Voltages Flash Address, Data, Control SPI Select System Interface PCB Rx Gate Tx Relay RAM RISC - ARM 7 Processor - Drivers - SPI - UART - Timers - Watchdog - Discrete I/O - Interrupts Interrupt DSP Interrupt Main Loop System I/O Tx Key Detect External Reference Detect/ Select Select 10MHz or 12.8MHz External 12.8MHz Internal TCXO 10MHz or 12.8MHz Rx L.O. Debug LEDs Test Synthesizers DIP Switch Ex L.O. 12.8MHz Lock Detects SPI 40MHz Clock RF PCB SPI Chip Selects Chip Selects Lock Detects 40MHz Digital PCB 40MHz Digital Clock The 40MHz synthesized digital clock is situated on the digital PCB. It is used to drive the entire digital circuitry. The 40MHz frequency synthesizer is implemented using an Integer_Nbased phase locked loop (PLL) IC. The PLL is a negative feedback loop, which continuously monitors and maintains the 40MHz VCXO to a fixed frequency and constant phase relationship with respect to a 12.8MHz reference. The 40MHz VCXO oscillator is electrically tuned using two varactors. The oscillator output is buffered before being distributed to the digital circuitry. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 27 2.2 Reference Switch Refer to Figure 2.4 on page 29. Synthesizer The external reference synthesizer consists of a programmable frequency synthesizer IC, a 12.8MHz VCXO, and a stable 10MHz or 12.8MHz reference frequency supplied to the reciter externally via a BNC connector on the rear panel. The synthesizer uses a phase-locked loop to lock the 12.8MHz VCXO to the external reference frequency. The synthesizer IC receives the divider and control information from the RISC processor via a 3-wire serial bus (clock, data and enable). When the data bits are latched in, the synthesizer processes incoming signals from the 12.8MHz VCXO feedback buffer (fvcxofb) and the external reference buffer (fref). A transistor is used as a unity gain 12.8MHz VCXO feedback buffer for the prescaler within the synthesizer IC. The 10MHz or 12.8MHz externally supplied reference is detected, buffered and divided down to the 100kHz divider reference within the synthesizer IC. The same divider reference is maintained by dividing the 12.8MHz VCXO feedback buffered signal using the programmable dividers of the synthesizer IC. Phase lock is achieved when both divider references have the same phase and frequency content (i.e. their difference is zero or DC). This is achieved by the digital phase detector (part of the synthesizer IC), which compares both divider references and delivers an error signal. A ±1mA charge pump circuit (also part of the synthesizer IC) and the passive loop filter circuit convert this error signal to a DC voltage (0 to 3V) to tune the 12.8MHz VCXO for correction. A loop filter with a bandwidth of 180Hz further filters the VCO control line reference side bands and spurious signals. Note The VCXO frequency increases as the control line voltage increases. VCXO The VCXO is implemented by using a varactor to linearly tune a 12.8MHz crystal unit over a specified frequency range. The frequency range provided will cover frequency drifts due to calibration, the temperature tolerance of the crystal unit, and the frequency stability of the externally supplied reference. 28 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 TB8100 Service Manual © Tait Electronics Ltd April 2004 Serial Bus Data Clock Chip Select/Latch Enable 10 or 12.8MHz External Reference External Reference Buffer fref Software Register /R Programmable VCO Divider /N Phase Detector Frequency Synthesizer IC Programmable Reference Divider External Reference Detector 8/9 Prescaler Charge Pump Lock Detect f VCOfb 12.8MHz VCXO Feedback Buffer Loop Filter Ext_Ref_Lock_Detect Ext_Ref_Det OFF / ON ON / OFF External Reference 12.8MHz VCO RISC Digital Switch Reference Switch Internal Reference 12.8MHz TCXO Ext_Ref_Ctrl RF Switch Buffer Buffer Digital Clock Synthesizer Reference Receiver Synthesizer Reference FCL Reference Internal/External Reference Clock Branch Figure 2.4 Reciter External Reference Block Diagram Reciter Circuit Description 29 Reference Switch The reference switch consists of the external reference detector, the hardware switch, and the digital switch. External Reference Detector A discrete NPN dual transistor pair is used as a low level signal detector. The Syn_Ref_Det signal has a high logic level when the externally supplied signal has the correct level. Hardware Switch The hardware switch is implemented using a discrete dual transistor pair. When the switch is off (default), it powers up the internal reference 12.8MHz TCXO and shuts down the external reference 12.8MHz VCXO. When the switch is on, it powers up the external reference 12.8MHz VCXO and shuts down the internal reference 12.8MHz TCXO. Digital Switch The digital switch is controlled by the RISC, which processes the Syn_Ref_Det and Lock Detect signals from the external reference synthesizer. The RISC controls the hardware switch using the Syn_Ref_Ctrl signal. The hardware switch is on if the Syn_Ref_Det and Lock Detect signals have a high logic level for a set time. In all other conditions the hardware switch is off. Internal/External Reference Clock Branch A complementary emitter follower, using NPN/PNP dual transistors, forms two clock buffer branches which distribute the internal or external references to the rest of the system. The branches provide a reasonable drive level at low impedance. 30 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 2.3 Receiver RF Circuitry Figure 2.5 Reciter Receiver RF Circuitry Block Diagram RF In Band Pass Filter 1 RF Amplifier 1 Low Pass Filter PIN Attenuator AGC Control Mixer Diplexer RF Amplifier 2 Band Pass Filter 2 6dB Pad AGC Detector Post-mixer Buffer 5dB Pad Crystal Filter IF Amplifier Anti-alias Filter IF Output Local Oscillator Front End The incoming signal from the BNC connector is fed through a triplet helical filter, followed by a simple low pass network which attenuates harmonics and spurious responses from the preceding filter. The signal is then amplified and passed through a low pass filter which provides immunity to interference from higher frequency out-of-band signals. Automatic gain control (AGC) is provided at this point by a PIN diode attenuator. The signal is now amplified again in a second RF amplifier, and is then fed through a band pass filter and 6dB pad to the mixer. Mixer The RF signal from the front end is converted down to the 70.1MHz IF by a high level (+17dBm local oscillator) mixer. The voltage controlled oscillator (VCO) generates a level of 20dBM which is fed to the mixer through a 3dB attenuator pad. A diplexer terminates the IF port of the mixer in 50Ω, thus ensuring a good match for all mixing products, as well as enhancing the linearity. The post-mixer buffer amplifier compensates for the insertion loss of the crystal filter, and any excess gain is reduced by the following 5dB attenuator pad. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 31 32 Reciter Circuit Description Serial Bus Data Clock Chip Select/Latch Enable 12.8MHz Reference Oscillator fref Software Register /R Programmable Reference Divider Programmable VCO Divider /N Phase Detector Frequency Synthesizer IC Lock Detect Output 64/65 Prescaler Charge Pump Lock Detect Circuitry f VCOfb VCO Feedback Attenuator Loop Filter VCO LNA Buffer Harmonic Filter Receiver VCO Fixed Slope Attenuator Final Driver +20dBm LO Figure 2.6 Reciter Receiver Synthesizer Block Diagram TB8100 Service Manual © Tait Electronics Ltd April 2004 IF Circuitry The signal from the mixer is fed to the IF amplifier through a 4-pole crystal filter which provides protection from strong off-channel signals. The IF amplifier is a two-transistor design with voltage and current feedback, which provides sufficient gain to drive the digital receiver. The 70.1MHz signal is finally passed to the analogue-to-digital converter (ADC) in the digital receiver via an anti-alias filter. This filter prevents IF noise at frequencies other than 70.1MHz, generated in the amplifier, from being sampled by the ADC at other Nyquist zones. Synthesizer The receiver synthesizer consists of a programmable frequency synthesizer IC, the receiver VCO, and a stable known reference. The synthesizer uses a phase-locked loop to lock the receiver VCO to a stable known frequency reference. The synthesizer IC receives the divider and control information from the RISC processor via a 3-wire serial bus (clock, data and enable). When the data bits are latched in, the synthesizer processes the incoming signals from the VCO feedback signal (fvcofb) and the reference oscillator (fref). The VCO feedback attenuator is a resistive divider that terminates the VCO feedback signal in a fixed low impedance (50Ω). This attenuates the VCO RF level down to a level suitable for the RF prescaler (within the synthesizer IC). A 12.8MHz temperature controlled crystal oscillator (TCXO) is used as the internal reference oscillator. When the TCXO is active, the receiver synthesizer is locked to an “internal reference mode” (by default). Alternatively, a phase-locked 12.8MHz voltage controlled crystal oscillator (VCXO) can be used as the external reference oscillator. When the VCXO is active, the receiver synthesizer is locked to an “external reference mode”. In operation only one oscillator is active at any given time. Refer to “Reference Switch” on page 28 for details on the phase-locked 12.8MHz external reference oscillator. The reference oscillators are buffered, branched, and divided down to the 6.25kHz (default) or 5kHz divider reference within the synthesizer IC. The same divider reference is maintained by dividing the VCO feedback signal using the prescaler and programmable dividers of the synthesizer IC. Phase lock is achieved when both divider references have the same phase and frequency content (i.e. their difference is zero or DC). This is achieved by the phase detector (part of the synthesizer IC), which compares both divider references and delivers an error signal. A ±4mA charge pump circuit (also part of the synthesizer IC) and the active loop filter circuit convert this error signal to a DC voltage (0 to 22V1) to tune the VCO for correction. The 1. The normal lock range is between 3V and 16V. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 33 loop filter has a bandwidth of 150Hz and filters the VCO control lines, reference side bands and spurious signals. Note The VCO frequency increases as the control line voltage increases. VCO The receiver VCO consists of a high Q VCO, low noise amplifier, harmonic filter, fixed slope attenuator, and a final driver. Refer to Figure 2.6 on page 32. High Q VCO The VCO BJT transistor operates in a common collector Colpitts oscillator, and uses a shorted quarter-wave ceramic coaxial resonator. The open end of the resonator is terminated by a combination of a high Q trimmer and varactor diodes. This forms a high Q resonator which is both mechanically and electronically tunable. Mechanical tuning is possible by adjusting the trimmer. Changes in the control voltage from the loop filter are applied to the varactors to facilitate electronic tuning. The oscillator has a drive level of +7dBm ±1dB. Low Noise Amplifier An N-channel dual gate MOSFET is used as a broad band matched Class A low noise amplifier. It has internal self-bias circuitry, and delivers an output of +12dBm (nominal) before entering compression. Harmonic Filter The VCO has a high second harmonic content. A third order low pass elliptic filter is used to attenuate this content. It has an insertion loss of 0.5dB with 10dB of attenuation at the second harmonics. Fixed Slope Attenuator and Final Driver A silicon-based BJT transistor is used as a broad band matched Class A final driver to drive the +20dBm local oscillator port of the mixer. This circuit delivers 20dB ±1dB of gain for a +3dBm fixed input level. To maintain a fixed input level, a fixed slope attenuator is introduced at the input to the final driver so that the attenuation rate (slope) decreases with an increase in frequency. The slope attenuator has 8dB of attenuation at the bottom of the band and a slope of –1dBattn /100MHz. The VCO frequency spans from either 370–410MHz, 400–450MHz or 470–510MHz according to the product type (refer to “Identifying the Reciter” on page 52). The VCO is tuned to either 70.1MHz below (low side injection) or above (high side injection) to produce the 70.1MHz IF signal at the output of the mixer. AGC The AGC is used to prevent the ADC from being overloaded by strong interfering signals present at the receiver antenna port. The AGC loop consists of a PIN diode attenuator, AGC buffer, and detector. The pick-off 34 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 point for the AGC is the output of the post-mixer buffer. The input signal to the AGC is buffered, amplified and then detected. The detected DC voltage is buffered and fed to PIN_CTRL to control the attenuation of the PIN attenuator. To prevent overload of the ADC, the peak level at its input should not exceed 0dBm. This corresponds to –30dBm at the antenna connector, and approximately –22dBm at the AGC pick-off point. The AGC operates over a range of approximately 11dB. The AGC circuit can be enabled or disabled using the Service Kit (Configure > Base Station > Channel Profiles > General tab). 2.4 Exciter RF Circuitry Refer to Figure 2.8 on page 37. Frequency Control Loop Audio modulation of the exciter synthesizer is implemented in the frequency control loop (FCL). It uses a three-point modulation scheme involving the FCL_VCXO and VCO signals. The FCL consists of reference oscillators, clock buffers, twisted ring counter phase detectors, low pass filters (LPFs), ADCs, the FCL processor and digital-to-analogue converters (DACs). Reference Oscillators Modulation to the FCL_VCXO reference oscillator requires the use of the FCL_VCXO_CTRL and SYN_VCO_MOD signals to apply: ■ a constant DC offset to the FCL_VCXO signal until it achieves frequency lock to the internal referenced TCXO; ■ frequency modulation to the FCL_VCXO and VCO simultaneously from the transmit audio signal; the transmit audio signal has a range of 0 to 3kHz. The modulated signal from the VCXO is attenuated by the bandwidth of the loop filter in the low pass filter (i.e. 150Hz). To obtain flat modulation across the audio band, the VCO is also modulated simultaneously to obtain a composite high pass filter response. Figure 2.7 shows the relationships between the frequency modulation gain characteristics of the VCXO and VCO. Clock Buffers The TCXO and VCXO signals are squared up and buffered as digital signals using hex inverters. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 35 Figure 2.7 Comparison of VCXO and VCO Modulation Responses Gain linear relationship proportianal to the RF frequency and FCL_GAIN, measured during calibration VCXO non-linear relationship, determined by CalVcoGain_Corrected, calculated from the calibration data VCO Frequency 0 150Hz 3kHz Twisted Ring Counter The VCXO and TCXO signals are phase shifted and multiplied by XOR (exclusive_or) logic. This is achieved using a twisted ring counter, which also divides both signals by four. Low Pass Filter There are two output signals from the twisted ring counter. Both signals have the sum and difference frequency contents of the TCXO and VCXO signals, but there is a 90° phase difference between them. I and Q low pass filters capture the difference frequency contents down to DC and integrate them to form two triangular waves, which are 90° out of phase with each other. This frequency is equal to a quarter of the difference frequency content of the TCXO and VCXO signals. The in-phase triangle frequency is referred to as “I channel” and the quadrature-phase triangle frequency is referred to as “Q channel”. ADC The I_Q channel triangular analogue waveforms are sampled and transformed to digits using a 16-bit ADC with a signal-to-noise ratio of 75dB. FCL Processor and DAC The FCL processor runs a DSP-based algorithm which takes the digitised signals, I_Q and transmit audio, and compares them to the transmit modulation calibration data. Using the compared results it attempts to lock FCL_VCXO to the TCXO, as well as modulate the FCL_VCXO and VCO signals to achieve modulation flatness across the transmit audio and VCO RF bands. The FCL processor achieves this by sending the digitised modulation code through a16-bit DAC. Here the code is translated to analogue signals which modulate FCL_VCXO and the VCO. The DAC has a signal -to-noise ratio of 70dB. 36 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 TB8100 Service Manual © Tait Electronics Ltd April 2004 Serial Bus Chip Select/Latch Enable Data Clock Digital Clock Buffer Digital Clock Buffer VCXO Modulation 12.8MHz FCL + DC Offset VCXO Oscillator 12.8MHz Reference Oscillator Digital Clock Buffer fref Software Register /R Lock Detect Output Programmable VCO Divider /N Phase Detector LPF LPF 64/65 Prescaler Charge Pump Lock Detect Circuitry Q Channel I Channel Frequency Synthesizer IC Programmable Reference Divider /4 Divide by 4 I-Q Exclusive OR Gate Twisted Ring Counter f VCOfb FCL_Q Varicap Diodes FM Demodulator FCL_I VCO Feedback Attenuator Loop Filter ADC ADC Frequency Control Loop VCO VcxoScale TripleScale PresTriDemod TripleScale LNA Buffer Harmonic Filter Exciter VCO Delay IntGain Fixed Slope Attenuator Final Driver FclMidPoint (DC value) 10dB Pad Fixed Attenuator VcoMod VcxoScale Exciter Control Circuit Digitised Tx Audio Delay Integrator FclFreqOffset (DC value) DSP based FCL Processor Ex_Key PA_Key +11dBm to PA DAC SYN_VCO_MOD FCL_VCXO_CTRL DAC Figure 2.8 Reciter Exciter Synthesizer Modulator Block Diagram Reciter Circuit Description 37 Synthesizer The exciter synthesizer consists of a programmable frequency synthesizer IC, the exciter VCO, and a modulatable frequency reference. The synthesizer uses a phase-locked loop to lock the exciter VCO to a modulatable frequency reference. The synthesizer IC receives the divider and control information from the RISC processor via a 3-wire serial bus (clock, data and enable). When the data bits are latched in, the synthesizer processes the incoming signals from the VCO feedback signal (fvcofb) and the reference oscillator (fref). The VCO feedback attenuator is a resistive divider that terminates the VCO feedback signal in a fixed low impedance (50Ω). This attenuates the VCO RF level down to a level suitable for the RF prescaler (within the synthesizer IC). The FCL_VCXO reference oscillator is modulated by the FCL. The FCL itself is locked to an internal reference 12.8MHz TCXO. When the TCXO is active, the exciter synthesizer is locked to an “internal reference mode” (by default). Alternatively, the FCL is locked to a phase locked 12.8MHz external reference oscillator. When this external oscillator is active, the exciter synthesizer is locked to an “external reference mode”. In operation only one reference oscillator is active at any given time. Refer to “Reference Switch” on page 28 for details on the phase-locked 12.8MHz external reference oscillator. The FCL_VCXO reference oscillator is buffered and divided down to the 6.25kHz (default) or 5kHz divider reference within the synthesizer IC. The same divider reference is maintained by dividing the VCO feedback signal using the prescaler and programmable dividers of the synthesizer IC. Phase lock is achieved when both divider references have same phase and frequency content (i.e. their difference is zero or DC). This is achieved by the phase detector (part of the synthesizer IC), which compares both divider references and delivers an error signal. A ±4mA charge pump circuit (also part of the synthesizer IC) and the active loop filter circuit convert this error signal to a DC voltage (0 to 22V1) to tune the VCO for correction. The loop filter has a bandwidth of 150Hz and filters the VCO control lines, reference side bands and spurious signals. Note The VCO frequency increases as the control line voltage increases. VCO The exciter VCO consists of a high Q VCO, modulation based on varicap diodes, low noise amplifier, harmonic filter, fixed slope attenuator, final driver and a 10dB fixed attenuator. 1. The normal lock range is between 3V and 16V. 38 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 High Q VCO The VCO BJT transistor operates in a common collector Colpitts oscillator, and uses a shorted quarter-wave ceramic coaxial resonator. The open end of the resonator is terminated by a combination of a high Q trimmer and varactor diodes. This forms a high Q resonator which is both mechanically and electronically tunable. Mechanical tuning is possible by adjusting the trimmer. Changes in the control voltage from the loop filter are applied to the varactors to facilitate electronic tuning. The oscillator has a drive level of +7dBm ±1dB. Modulation Based on Varicap Diodes Modulation on the VCO is provided by an auxiliary varicap-based control circuit which provides a modulation gain of 5kHz/Vp. Low Noise Amplifier An N-channel dual gate MOSFET is used as a broad band matched Class A low noise amplifier. It has internal self-bias circuitry and delivers an output of +12dBm (nominal) before entering compression. Harmonic Filter The VCO has a high second harmonic content. A third order low pass elliptic filter is used to attenuate this content. It has an insertion loss of 0.5dB with 10dB of attenuation at the second harmonics. Fixed Slope Attenuator, Final Driver and 10dB Fixed Attenuator To provide a drive of +20dBm, a silicon-based BJT transistor is used as a broad band matched Class A final driver. This circuit delivers 20dB ±1dB of gain for a +3dBm fixed input level. To maintain a fixed input level, a fixed slope attenuator is introduced at the input to the final driver so that the attenuation rate (slope) decreases with an increase in frequency. The slope attenuator has 8dB of attenuation at the bottom of the band and a slope of –1dBattn /100MHz. A 10dB fixed resistive pad attenuator provides a signal level of +11dBm ±2dB to the input port of the PA, providing better reverse isolation. The VCO frequency spans from either 400–440MHz, 440–480MHz or 470–520MHz according to the product type (refer to “Identifying the Reciter” on page 52). Exciter Control Circuit This circuit powers up and shuts down the exciter final driver in a controlled manner. During transient adjacent channel power and cyclic keying, the exciter needs to power up and shut down in a specified time sequence. The exciter control circuit uses Ex_Key to power up or shut down the VCO final driver, and PA_Key to power up or shut down the PA driver. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 39 2.5 System Interface PCBs The reciter can be fitted with an optional system interface PCB which provides the links between the reciter’s internal circuitry and external equipment. This PCB is securely mounted to the reciter’s chassis and is connected to the digital PCB with a flexible connector. The system interface PCB is fitted with industry-standard connectors and several standard types are available for different applications. The circuitry on the system interface PCB provides additional signal processing so that the outputs meet standard system requirements. It also enables the PCB to identify itself to the reciter control circuitry. The system interface PCB is removable, which makes it possible to change the application of a reciter by removing one type of PCB and fitting another. Only one system interface PCB can be fitted to a reciter at any one time. The following section provides an overview of all the system interface circuitry. However, not all the circuitry described here will be fitted to any particular system interface PCB. The different types of PCB and their main features are listed in the following table. Refer also to Figure 2.9 on page 41. System Interface PCB Isolated Isolated E&M non-isolated isolated isolated isolated unbalanced audio ✓ ✓ ✓ ✓ RSSI ✓ ✓ ✓ Rx Gate ✓ ✓ ✓ ✓ Tx Key ✓ ✓ ✓ ✓ digital inputs 10 10 6 1 digital outputs 2 2 2 3 Tx relay output ✓ ✓ ✓ auxiliary power ✓ ✓ ✓ Feature Standard balanced audio opto-coupled input ✓ opto-coupled output ✓ third-party connector Note 40 Reciter Circuit Description ✓ ✓ ✓ TaitNet ✓ ✓ This section provides details on the system interface PCBs available at the time of publication. Other types may be developed for future applications. TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 2.9 Reciter System Interface PCB Block Diagram Audio I/O Third-party I/O Balanced Audio Input Third-party I/O Unbalanced Audio Input # Third-party I/O Third-party I/O Balanced Audio Output Digipots # Mutes Unbalanced Audio Output Digital Sub-system SIO Bus Digital Outputs External Interface SIO Bus Reciter Interface SIPOs* Third-party Audio Third-party Connector System Interface Identification SIO Bus PISOs* Digital Inputs RSSI RSSI Rx Gate Rx Gate Tx Key Conventional Signalling Interface Tx Relay Tx Key Tx Relay Opto-coupled Output Opto-coupled Input Power Supply Control Connections to the Reciter *SIPO = Serial In, Parallel Out PISO = Parallel In, Serial Out Auxiliary Power # transformers not fitted to standard system interface PCB The system interface PCB has two connections to the reciter: a 40-way flexible connection, and a high-speed connection. The 40-way connection is essential to the system interface PCB’s operation. It provides power and communications from the reciter, along with all the other system interface inputs and outputs. The high-speed connection is only used on system interface PCBs which require a high rate data connection to the reciter processor. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 41 Balanced Audio Output The balanced audio output is a 600Ω audio interface. The output level can be set over the range –20dBm to +10dBm, for 60% modulation. The output level can be set with a resolution of 0.1dB. This output may be either transformer isolated or just AC coupled. Unbalanced Audio Output The unbalanced audio output should only be used with high impedance loads (>10kΩ). The output level can be set over the range 0.3Vpp to 3.0Vpp, for 60% modulation. The output level can be set with a resolution of 0.1Vpp. This output is AC coupled. Balanced Audio Input The balanced audio input is a 600Ω audio interface. The input level can be set over the range –20dBm to +10dBm, for 60% modulation. The input level can be set with a resolution of 0.1dB. This input may be either transformer isolated or just AC coupled. Unbalanced Audio Input The unbalanced audio input is a high impedance input (>10kΩ). The input level can be set over the range 0.3Vpp to 3.0Vpp, for 60% modulation. The input level can be set with a resolution of 0.1Vpp. This input is AC coupled. RSSI The RSSI output is DC coupled and provides a voltage proportional to the received signal strength with a user-defined characteristic. Rx Gate The Rx Gate output is an open collector output. The transistor is on when a valid signal is received. The maximum current rating of this output is 100mA. The maximum voltage that should be applied to this output is 30V. Tx Key The Tx Key input has a high input threshold guaranteed to be >5V. The low input threshold is 2V. A low input keys the transmitter. Digital Inputs The digital inputs have 5V logic thresholds and are active low. The maximum external pull-up voltage on these inputs is 20V. Digital Outputs The digital outputs are open collector outputs. The maximum current rating of these outputs is 100mA. The maximum voltage that should be applied to these outputs is 30V. Tx Relay Driver Output The Tx relay driver output is an open collector output. The maximum current rating of this output is 250mA. The maximum voltage that should be applied to this output is 30V. Opto-coupled Keying Input This input operates in parallel with the Tx Key input. Although it has the same functionality as the Tx Key input, it is electrically isolated. The input may be driven with a voltage in the range ±10V to ±60V. The input current is regulated to 10mA. 42 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 Opto-coupled Gate Output This output operates in parallel with the Rx Gate output. Although it has the same functionality as the Rx Gate output, it is electrically isolated. The maximum output current is 120mA. The maximum voltage that should be applied across this output is ±350V. Third-party Connector The third-party connector provides access to audio, keying, gating and digital I/O signals to allow the integration of third-party modules such as scramblers. Power Supplies The system interface PCB is powered via the 40-way flexible connection to the reciter. 2.6 Power Supply The reciter is designed to operate from the +28V regulated supply provided by the PMU. The nominal +28V supply enters the reciter digital PCB and passes through an overcurrent and overvoltage protection section before being distributed. The protected +28V output supplies the control comparators, fan switch, and main regulators. There is one regulator on the digital PCB and another on the RF PCB. RF PCB The main regulator is a switched mode converter that has two outputs: the flyback portion generates +8.5V, and the buck portion generates +5.3V. The +8.5V supply is regulated to +8.0V for reticulation to the RF circuits, either directly, or via switching circuits used in power saving modes. The +8.5V supply is also used to power the analogue sections of the system interface PCB (via the digital PCB). The +5.3V supply is regulated to +3.3V to power the RF synthesizers. The RF PCB has a charge pump converter that generates +23V from both the +5.3V and +8.5V supplies. This is used to supply the active loop filters of the RF synthesizers. The +8.5V output and the +5.3V supply to the charge pump can be switched as part of the power saving modes. Digital PCB The main regulator is a switched mode converter that has two outputs: the flyback portion generates +5.3V, and the buck portion generates +3.3V. The +5.3V output supplies the op amps associated with the CODECs and is distributed with regulators: +5V for the ADC, +5V for the system, and +3V for the 40MHz clock circuitry. The +5.3V and +5V regulated supplies can be switched as part of the power saving modes. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 43 Figure 2.10 Reciter Power Supply Block Diagram +28V Filter +28V 5.3V Dual SMPS Regulator 8.5V 3.3V Regulator 3.3V Charge Pump 23V 8VRX PWD_EX Power Switches PWD_RX 8VEX PWD_ON 8V 8V Regulator RF PCB Digital PCB 8.5V to SIF To Fan +28V to RF PCB Switch Fan Switch Analogue 5.3V Filter 5V Regulator Digital 5.3V Filter Control Analogue 5V 5V Regulator 3V Regulator +28V Polyswitch + Zener Dual SMPS Regulator Filter 3.3V System 5V Analogue 3V Digital 3.3V Power Switch 5.3V +28V PWD_ON Comparators SD Linear 5V Regulator Power Switch Analogue 3.3V Power Switch Analogue 3.3V PWR_GOOD PWD_RX 3V Lock-out Circuit* DSP Low Regulator 2.5V *To prevent DSP latch-up 2.5V Protection Circuit 3.3V to SIF SIF = system interface PCB 5V to SIF 44 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 The +3.3V output is distributed to the remaining circuitry and to the +2.5V regulator for the DSP. These are switched as part of the power saving modes. The +3.3V output is also supplied to the system interface PCB via a protection circuit. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 45 46 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 2.11 b c d e f g h i j 1) 1! 1@ 1# 1$ 1% 1^ 1& 1* 1( Identifying the Circuitry on the Digital and System Interface PCBs system interface PCB CODECs SRAM 1( RISC JTAG connector (factory use only) b flash memory 1* RISC DSP DSP JTAG connector (factory use only) main digital system 1& c power supply digital IF and clock DDC 1^ ADC d 40MHz digital clock 1% 70.1MHz IF 12.8MHz reference 1$ audio e high speed data connector third-party connector 1# f g 1@ h 1! i j 1) UHF (H band) reciter shown fitted with isolated system interface PCB TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Circuit Description 47 48 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 2.12 b c d e f g h i j 1) 1! 1@ 1# 1$ 1% 1^ 1& 1* 1( 2) 2! 2@ 2# Identifying the Circuitry on the RF PCB 2# external reference input b mixer and post-mixer buffer 2@ receiver VCO c receiver VCO trimmer IF tuning elements 2! receiver synthesizer d IF TCXO 2) audio buffers e exciter VCO exciter VCO trimmer 1( exciter synthesizer f exciter RF output g FCL 1* FCL buffers power supply external reference switch/internal VCXO reference 1& AGC h front end 1 front end first helicals i front end 2 front end second helicals receiver RF input j 1^ Note: In order to show as much of the circuitry as possible in the photograph, the SMD shields have been removed. 1) 1% 1! 1@ 1$ UHF (H band) reciter shown TB8100 Service Manual © Tait Electronics Ltd April 2004 1# Reciter Circuit Description 49 50 Reciter Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 3 Reciter Servicing Important This equipment contains devices which are susceptible to damage from static charges. Refer to “ESD Precautions” on page 15 for more information on antistatic procedures when handling these devices. This chapter provides information on how to identify, remove and replace the main mechanical parts and individual PCBs. Figure 3.6 on page 65 identifies the main mechanical parts, and Figure 3.1 on page 53 identifies the individual PCBs. “Identifying the Reciter” on page 52 explains how to identify the model and hardware configuration of a reciter from its product code. Note TB8100 Service Manual © Tait Electronics Ltd April 2004 For the sake of simplicity and clarity, the instructions and illustrations in this chapter refer to a UHF (H band) reciter fitted with an isolated system interface PCB. However, the same basic procedures and techniques apply to other models of reciter and system interface PCB. Reciter Servicing 51 3.1 Disassembly and Reassembly Identifying the Reciter You can identify the model and hardware configuration of a reciter by referring to the product code printed on a label on the rear panel. The meaning of each character in the product code is explained in the table below. Note This explanation of reciter product codes is not intended to suggest that any combination of features is necessarily available in any one reciter. Consult your nearest Tait Dealer or Customer Service Organisation for more information regarding the availability of specific models and options. Product Code Description TBAXXXX-XXXX 4 = reciter TBA4XXX-XXXX 0 = default TBA4XXX-XXXX Frequency Band and Sub-band B2 = 136MHz to 156MHz B3 = 148MHz to 174MHz C2 = 174MHz to 193MHz C3 = 193MHz to 225MHz H1 = 400MHz to 440MHz H2 = 440MHz to 480MHz H3 = 470MHz to 520MHz K2 = 762MHz to 870MHza TBA4XXX-XXXX System Interface PCB 000 = no system interface PCB fitted 0A0 = standard 0B0 = isolated 0C0 = isolated E & M 0T1 = TaitNet TBA4XXX-XXXX 0 = default a. The actual frequency coverage in this band is: Transmit: 762MHz to 776MHz, and 850MHz to 870MHz Receive: 792MHz to 824MHz 52 Reciter Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 3.1 Identifying the Reciter PCBs digital PCB RF PCB system interface PCB UHF (H band) reciter shown fitted with isolated system interface PCB; RF PCB shown with shields removed for clarity TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Servicing 53 Screw Torque Settings The recommended torque settings for the screws and nuts used in the reciter are as follows: Location / Function ■ securing the side covers to the heatsink and front and rear panels ■ securing the front and rear panels to the heatsink ■ securing the handle to the front panel ■ securing the PCBs to the heatsink Driver/ Spanner Torque Size 0.5N·m / 4.5lbf·in T10 M3 securing the SMA connector to the front panel 0.3N·m / 2.5lbf·in T8 M2.5 securing the BNC/TNC connectors to the rear panel 1.7N·m / 15lbf·in 11mm AF Removing the Covers 1. Remove the M3 Torx screws securing the covers to the heatsink, and to the front and rear panels. Lift off the covers. Removing the Front and Rear Panels The circled numbers in the following instructions refer to Figure 3.2. 54 Reciter Servicing 1. Remove the four M2.5 Torx screws b securing the SMA connector to the heatsink and to the front panel. 2. Desolder the centre pin of the SMA connector c from the RF PCB and remove the connector. 3. Remove the two M3 Torx screws d securing the handle to the heatsink. 4. Remove the M3 screw e securing the front panel to the heatsink, and remove the front panel. 5. If necessary, remove the two M3 screws securing the fan duct f to the heatsink. 6. Remove the vent guard clip g from the rear panel. 7. Remove the two M3 Torx screws h securing each rear panel to the heatsink. If you want to remove the rear panel on the RF side, first unplug the coaxial cables from the RF PCB. TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 3.2 Removing the Front and Rear Panels front view rear view digital side RF side b e d g RF side f c each h 2rearforpanel Refitting the Front and Rear Panels The circled numbers in the following instructions refer to Figure 3.2. 1. If removed previously, refit the fan duct f to the heatsink and secure with the two M3 Torx screws. 2. Refit the front panel and secure to the heatsink with the M3 Torx screw e. 3. Secure the handle to the heatsink with the two M3 Torx screws d. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Servicing 55 4. Secure the SMA connector to the heatsink and front panel with the four M2.5 Torx screws b. 5. Resolder the centre pin of the SMA connector c to the RF PCB. 6. Refit the rear panel to the heatsink and secure with the two M3 Torx screws h. If you have removed the rear panel on the RF side, reconnect the coaxial cables to the RF PCB. 7. Refit the vent guard clip g. Refitting the Covers 1. Slide each cover into place over the front and rear panels. Make sure the holes in the covers line up with the threaded holes in the heatsink and front and rear panels. 2. Press the covers firmly into place and secure with the M3 Torx screws. Note 3.2 The covers are not interchangeable. Each cover must be fitted to the correct side and in the correct orientation. Replacing the Digital PCB Important You must reprogram and recalibrate the reciter after replacing the digital PCB. Refer to “Reprogramming and Recalibration” on page 59. Refer to Section 3.1 “Disassembly and Reassembly” for details on removing and refitting the covers and front and rear panels. The circled numbers in the following instructions refer to Figure 3.3. Removal 56 Reciter Servicing 1. Remove the digital side cover and the front panel. 2. Disconnect the flexible connectors to the system interface PCB b and RF PCB c from their respective sockets on the digital PCB. 3. Disconnect the 70.1MHz IF d and 12.8MHz reference e coaxial cables. 4. Remove the M3 Torx screws securing the PCB to the heatsink. 5. Carefully lift the PCB upwards off the locating pins f and remove it from the heatsink, feeding the coaxial cables and flexible connector through the slot in the PCB. Take care not to dislodge the flexible connector from its socket on the RF PCB. TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 3.3 Replacing the Digital and System Interface PCBs g g b f d e c f TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Servicing 57 Refitting 1. To refit the PCB, follow the removal instructions in reverse order. Important Make sure the insulator sheet is correctly positioned and flat on the heatsink. Although this sheet is an electrical insulator, it is also thermally conductive and must allow the PCB to sit as flat as possible to provide effective heatsinking. Operating the reciter without the insulator sheet in place will result in permanent damage to the digital or system interface PCBs. Important Make sure the flexible connectors are correctly positioned and latched in their sockets, as shown in Figure 3.4. Note Figure 3.4 Before tightening the screws, press the PCB down over the locating pins so that it is firmly seated against the heatsink. Then tighten the M3 Torx screws to the correct torque, working from the centre of the PCB to the edges. Reconnecting the Flexible Connectors blue stripe on same side as latch 58 Reciter Servicing latch pushed fully down at both ends flexible connector inserted straight into socket TB8100 Service Manual © Tait Electronics Ltd April 2004 Reprogramming and Recalibration If you have replaced the digital PCB, you will have to reprogram and recalibrate the reciter as described in the table below. Procedure 3.3 Details ■ reprogram the product code ■ reprogram the reciter type reprogram this information into the reciter using the Calibration Kit software; refer to the Calibration Kit documentation for more details reprogram the feature licence keys (if necessary) you will need to reprogram new feature licence keys into the reciter to re-enable any software features that were previously enabled; you will need to use the Service Kit software to do this; contact your nearest Tait Customer Service Organisation for further details about obtaining feature licence keys replace the serial number label the serial number of the reciter will change to the number already programmed into the replacement digital PCB; stick the new serial number label onto the rear panel ■ calibrate the exciter ■ calibrate the RSSI ■ calibrate the audio ■ adjust the receiver lock band (switching range) ■ tune the receiver ■ adjust the exciter lock band carry out these procedures in the order shown using the Calibration Kit software; refer to the Calibration Kit documentation for more details Replacing the System Interface PCB Important You must reprogram and recalibrate the reciter after replacing the system interface PCB. Refer to “Reprogramming and Recalibration” on page 60. Refer to Section 3.1 “Disassembly and Reassembly” for details on removing and refitting the covers and front and rear panels. The circled numbers in the following instructions refer to Figure 3.3 on page 57. Removal 1. Remove the digital side cover and rear panel. 2. Disconnect the flexible connector to the digital PCB b from the socket on the system interface PCB. 3. Remove the M3 Torx screws securing the PCB to the heatsink. 4. Carefully lift the PCB upwards off the locating pins g and remove it from the heatsink. TB8100 Service Manual © Tait Electronics Ltd April 2004 Reciter Servicing 59 Refitting 1. To refit the PCB, follow the removal instructions in reverse order. Important Make sure the insulator sheet is correctly positioned and flat on the heatsink. Although this sheet is an electrical insulator, it is also thermally conductive and must allow the PCB to sit as flat as possible to provide effective heatsinking. Operating the reciter without the insulator sheet in place will result in permanent damage to the digital or system interface PCBs. Important Make sure the flexible connector is correctly positioned and latched in its socket, as shown in Figure 3.4 on page 58. Note Reprogramming and Recalibration PCB Type when the replacement system interface PCB is a different type from the original when the replacement system interface PCB is the same type as the original 60 Reciter Servicing Before tightening the screws, press the PCB down over the locating pins so that it is firmly seated against the heatsink. Then tighten the M3 Torx screws to the correct torque, working from the centre of the PCB to the edges. If you have replaced the system interface PCB, you will have to reprogram and recalibrate the reciter. The actual procedures required will depend on whether or not the replacement PCB is the same type as the original, as shown in the table below. Procedure ■ reprogram the product code ■ reprogram the reciter type Details reprogram this information into the reciter using the Calibration Kit software; refer to the Calibration Kit documentation for more details calibrate the audio carry out this procedure using the Calibration Kit software; refer to the Calibration Kit documentation for more details calibrate the audio carry out this procedure using the Calibration Kit software; refer to the Calibration Kit documentation for more details TB8100 Service Manual © Tait Electronics Ltd April 2004 3.4 Replacing the RF PCB Important You must recalibrate the reciter after replacing the RF PCB. Refer to “Recalibration” on page 63. Refer to Section 3.1 “Disassembly and Reassembly” for details on removing and refitting the covers and front and rear panels. Unless otherwise indicated, the circled numbers in the following instructions refer to Figure 3.5. Removal Refitting 1. Remove both covers and the front panel. 2. Disconnect the flexible connector to the digital PCB c from its socket on the digital PCB (refer to Figure 3.3 on page 57). 3. Disconnect the 70.1MHz IF d and 12.8MHz reference e coaxial cables from their sockets on the digital PCB (refer to Figure 3.3). 4. Disconnect the RF input b and external reference c coaxial cables from their sockets on the RF PCB. 5. Remove the M3 Torx screws securing the PCB to the heatsink. 6. Carefully lift the PCB upwards off the locating pins d and remove it from the heatsink, feeding the coaxial cables and flexible connector through the slot in the heatsink. 1. Make sure that the 70.1MHz IF and 12.8MHz reference coaxial cables are secure in their sockets on the bottom of the RF PCB. 2. Make sure that the flexible connector is correctly positioned and latched in its socket on the bottom of the RF PCB (refer to Figure 3.4 on page 58). 3. Refit the PCB, following the removal instructions in reverse order. Note TB8100 Service Manual © Tait Electronics Ltd April 2004 Before tightening the screws, press the PCB down over the locating pins so that it is firmly seated against the heatsink. Then tighten the M3 Torx screws to the correct torque, working from the centre of the PCB to the edges. Reciter Servicing 61 Figure 3.5 Replacing the RF PCB b d c d 62 Reciter Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Recalibration If you have replaced the RF PCB, you will have to recalibrate the reciter as described in the table below. Important Do not adjust the IF. Procedure ■ calibrate the exciter ■ calibrate the RSSI ■ adjust the receiver lock band (switching range) ■ tune the receiver ■ adjust the exciter lock band TB8100 Service Manual © Tait Electronics Ltd April 2004 Details carry out these procedures in the order shown using the Calibration Kit software; refer to the Calibration Kit documentation for more details Reciter Servicing 63 64 Reciter Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 3.6 Reciter Mechanical Assembly Description b c d e f g h i j 1) 1! 1@ IPN 70.1MHz IF and 12.8MHz reference coaxial cables 219-02849-XX flexible connector 219-02850-XX RF input coaxial cable 219-02851-XX external reference coaxial cable 219-02852-XX SMA connector 240-02155-XX vent guard clip 303-50108-XX handle 308-01065-XX heatsink 308-13148-XX RF side cover 316-06795-XX front panel 316-06796-XX digital side cover 316-06797-XX g i 2! j d e 1$ 1@ 1^ x24 1% x14 1% x4 1^ x8 rear panel - digital side; changes according to the system interface PCB fitted: standard, isolated, isolated E & M TaitNet none 316-06798-XX 316-06799-XX 316-06802-XX 1# 1$ 1% 1^ fan duct 316-06804-XX rear panel - RF side 316-06805-XX M3x6mm countersunk Torx screw 345-40460-XX M3x8mm pan head Torx screw with spring & flat washers 345-40470-XX 1& 1* 1( 2) M2.5x8mm pan head Torx screw 345-40490-XX M3x12mm pan head Torx Taptite screw 349-02065-XX 4–40 UNC screw lock 354-01043-XX thermally conductive insulator sheet 362-01120-XX 2! 2@ 2# RF PCB 2# 1( x2 1& x4 1% c f digital PCB system interface PCB 2) 1% Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. 1! b x2 1# 1* x2 TB8100 Service Manual © Tait Electronics Ltd April 2004 x2 h 1^ x16 c 2@ 1% x11 1) Reciter Servicing 65 66 Reciter Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 4 Power Amplifier Circuit Description The TB8100 power amplifier (PA) is a modular design with the circuitry divided between separate PCBs. These PCBs are assembled onto a heatsink in different configurations in different models. Figure 4.1 below shows the configuration for a 100W PA, along with the main inputs and outputs for power, RF and control signals. The 100W PA consists of: ■ a 6W PCB ■ two quadrature-combined 60W PCBs ■ a splitter PCB and a combiner PCB ■ a low pass filter and directional coupler PCB ■ a control PCB. The configuration of the 50W PA is similar, but it uses only one 60W PCB and does not require the splitter or combiner PCBs. The 5W PA does not use the 60W, splitter or combiner PCBs. RF interconnect PCBs are also used in some configurations to connect the PCBs together. The type of interconnect PCB used depends on the configuration of the PA. Figure 5.1 on page 79 shows the different configurations for the 5W, 50W and 100W PAs. The locations of the main circuit blocks on the PCBs are shown in Figure 4.3 on page 75. PA High Level Block Diagram 60W PCB Splitter PCB RF RF I/P + PA Key RF 6W PCB RF Combiner PCB Figure 4.1 DC RF RF DC Control & Monitor 28VDC I/P DC Control & Monitor System Control Bus TB8100 Service Manual © Tait Electronics Ltd April 2004 Control & Monitor Control PCB RF O/P RF 60W PCB Low-Pass Filter & Directional Coupler PCB Ambient Air Temperature Sensor PCB Power Amplifier Circuit Description 67 4.1 Microprocessor Control Circuitry Refer to Figure 4.2 on page 70. The PA has a microprocessor which performs the following functions: ■ monitors the operating conditions of the PA ■ controls the RF power level ■ reports faults (by generating alarms) ■ takes preventative action to protect the PA under fault conditions. The alarms and diagnostics are accessed through I2C bus messages via the reciter, control panel and Service Kit software. There are no manual adjustments in the PA because all the calibration voltages and currents required to control and protect the PA are monitored by the microprocessor. The software also automatically detects the PA configuration and controls the PA accordingly. Diagnostics and Alarms The diagnostic functions and alarms monitored by the PA include: ■ the temperature of the 6W PCB ■ the temperatures of 60W PCB 1 (50W and 100W PAs) and 60W PCB 2 (100W PA) ■ the ambient temperature of the intake air1 ■ forward and reverse power ■ load VSWR ■ the transmit current of the 6W driver transistor ■ the transmit current of the final transistors on 60W PCB 1 (50W and 100W PAs) and 60W PCB 2 (100W PA) ■ the current imbalance between the final transistors on 60W PCBs 1 and 2 (100W PA) ■ the supply voltage ■ the summary alarm. Most alarms have two thresholds. The first threshold activates the alarm and is usually set by the user via the Service Kit software. The second threshold defines the limit of operation of the PA and the software will either foldback the RF transmit power or suspend transmission until the fault condition is recovered. The values for the second threshold are set in the factory and cannot be changed. In all instances there is a small amount of hysteresis between the value at which the alarm, foldback or shutdown activates and the value at which the alarm or shutdown is cleared. 1. Ambient temperature is defined as the temperature of the air at the intake to the cooling fan. 68 Power Amplifier Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 A red LED visible from the front panel of the PA will light to indicate a summary alarm. For a more detailed description of alarms and diagnostics refer to the Service Kit User’s Manual or on-line help. PA-Key The PA is keyed by a +8VDC signal which is superimposed on the RF signal on the coaxial input cable. The key-up sequence requires the RF input (+11dBm) to be turned on and stable before the PA is keyed on. When the PA is keyed off, the RF input is turned off only when the key-down sequence is complete. Foldback The PA control circuitry will reduce the RF output power to Pmin when any one of the following fault conditions occurs:1 ■ the temperature of the 6W PCB, 60W PCB 1 or 60W PCB 2 exceeds the maximum allowable temperature ■ the supply voltage drops to between 24 and 26VDC or rises to between 30 and 32VDC the load VSWR is ≥10:1 (foldback is deactivated when the VSWR <5:1) ■ the transmit current of the 6W driver transistor, 60W final transistor 1 or 60W final transistor 2 exceeds the maximum allowable current. ■ Pmin is defined as follows: Model Pmin 5W 1W 50W 5W 100W 10W 1. The accuracy of the measurement of the parameter values is subject to the tolerances listed in the Specifications Manual. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Circuit Description 69 RF In Control PCB PA_KEY RF Detect AND -3V -3V Power Supply +5V Power Supply +10V +10V Power Supply +2.5V Power Supply ADC DAC ADC 6W Driver +28V Microprocessor power control RF Block 1W Pre-driver driver bias 100mW Gain Block driver current PIN Attenuator ADC DAC Splitter PCB ambient air temperature High Pass Filter final 2 bias driver temperature 6W PCB ADC final 2 drive current DAC 60W PCB ADC 60W 60W PCB Final +28V 60W final 1 drive current 50Ω Load final 1 bias Final final 1 temperature +28V DAC DAC Combiner PCB RF power setting This drawing shows the circuitry for the 100W PA. transient wave shape Power Amplifier Circuit Description 50Ω Load ADC ADC Low Pass Filter I2C Fan Buffer Directional Coupler LPF/Directional Coupler PCB forward power 70 reverse power System Control Bus RF Out Figure 4.2 PA Control, RF and Power Supply Circuitry Block Diagram TB8100 Service Manual © Tait Electronics Ltd April 2004 final 2 temperature Shutdown The PA software will prevent transmission under the following conditions: the following calibration procedures were not completed successfully: ■ ■ 6W driver transistor, 60W final transistor 1 or 60W final transistor 2 bias ■ detector bias ■ supply voltage ■ output power ■ the supply voltage drops below 24VDC or exceeds 32VDC ■ the transmit current of the 6W driver and 60W final transistors does not reduce to a safe level after foldback ■ the configuration of the PA is invalid. Calibration You can calibrate the bias currents and output power settings of the 6W driver and 60W final transistors using the Calibration Kit software. However, this calibration is only required if components in the RF signal path have been altered. Power Control The PA has a power control circuit which keeps the output power constant and protects the PA from VSWR mismatch conditions. The control circuit monitors forward and reverse power and these measurements are used to: ■ determine forward and reverse power ■ keep the output power constant ■ foldback the power under mismatch conditions ■ calculate VSWR. The power level is set by requesting the power level in Watts via an I2C bus message. The minimum size of a power step is 1W and the range of output power settings is: Model Output Power Range 5W 1 to 5W 50W 5 to 50W 100W 10 to 100W The forward power, reverse power and load VSWR measurements may also be requested via I2C bus messages. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Circuit Description 71 The foldback loop is analogue until the VSWR reaches 10:1, at which point the microprocessor initiates foldback. The microprocessor and control loop are also used to shape the RF signal envelope during key-on and key-off transients. Fan Control The fan is supplied from a +24V controlled supply on pin 13 of the IDC connector (ground is on pin 14). The status of the fan supply voltage is dependent on the operating temperature of the PA. The fan is turned on when the PA operating temperature exceeds the user-defined thresholds set using the Service Kit software. The fan remains on until the operating temperature of the PA falls to 5°C below the threshold temperature. The fan is also turned on for 30 seconds before an ambient temperature measurement is taken. This is necessary as the ambient temperature sensor requires airflow to perform an accurate temperature measurement. Power is supplied to the fan via the 16-way ribbon cable from the PA to the subrack interconnect PCB. From there it is fed through the control panel to the fan. If two PAs are fitted in a subrack, either PA will turn on the fan when required. Power Supplies The PA operates off a single +28VDC external power supply. The normal range of operation is +26 to +30VDC. If the supply voltage falls to between +24 and +26VDC or rises to between +30 and +32VDC, the PA will reduce its output power to foldback levels. If the supply voltage falls below +24VDC or rises above +32VDC, the PA will cease transmission (shutdown). The PA also has four internal power supplies to produce –3, +2.5, +5 and +10VDC. Temperature Monitoring The PA monitors the temperatures of the 6W PCB, 60W PCB 1 and 60W PCB 2. The operating temperatures can be requested via an I2C bus message. If any PCB reaches the designated maximum temperature, the PA software will report an alarm via the I2C bus. The maximum temperature thresholds may be set using the Service Kit software. In addition to activating alarms, the PCB temperatures are also used to activate the PA fan, and power foldback. The foldback thresholds are set in the factory and cannot be 72 Power Amplifier Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 adjusted by the user. A recovery hysteresis of 5°C is applied to all temperature thresholds. Ambient Air Temperature Sensor The PA ambient air temperature sensor PCB may be fitted in one of two positions. It is inserted through the appropriate slot in the control PCB and plugs into a 3-way connector. The sensor PCB is positioned between the heatsink fins and requires forced airflow to perform an accurate measurement. Note 4.2 You must fit the sensor PCB in the correct location to ensure that the temperature of the airflow over the sensor is nearest the ambient temperature of the air at the intake to the cooling fan. Figure 5.1 on page 79 shows the correct location of the sensor PCB in each model of PA. RF Circuitry Refer to Figure 4.2 on page 70. 6W PCB The 11dBm (±2dB) RF input is fed to the variable PIN diode attenuator which provides power control. From the PIN diode attenuator the signal is fed via a 100mW gain block and a 1W gain stage to a 6W transistor where it is amplified to the final output level of 6W. This 6W transistor forms the output stage of the 5W PA and is the driver stage for the 50W and 100W PAs. The gain block and 1W transistor operate off a +10V switched supply, while the 6W driver transistor operates off a +28V supply. The 6W PCB also has circuitry to monitor the drain current and temperature of the 6W transistor, and the presence of an RF input signal. 60W PCB The output from the 6W PCB is fed to the 60W final transistor which amplifies the signal to an output power of 60W. The 60W transistor operates off a +28V supply. The 60W PCB also has circuitry to monitor the drain current and temperature of the 60W transistor. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Circuit Description 73 Low Pass Filter and Directional Coupler PCB The output from the 60W PCB is fed to the RF output connector via a low pass filter (LPF), to attenuate harmonics, and a dual directional coupler. The directional coupler senses forward and reverse power which is rectified and passed to the control circuitry for metering, alarm and power control. The directional coupler is on the output side of the LPF to measure true output power. Splitter and Combiner PCBs In the 100W PA the output from the 6W PCB is split through a 3dB hybrid coupler on the splitter PCB to drive two 60W PCBs in quadrature. The outputs from these two PCBs are then combined by another 3dB hybrid coupler on the combiner PCB before being fed to the LPF/directional coupler PCB. Interconnect PCBs Because of the modular design of the PA, interconnect PCBs are used in certain models to connect PCBs that are physically separated on the heatsink. They have no components and their only function is to link two parts of the circuit together. The interconnect PCBs are shown in Figure 5.1 on page 79. 74 Power Amplifier Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 4.3 b c d e f g h i j 1) 1! 1@ 1# 1$ 1% 1^ 1& 1* 1( 2) 2! 2@ 2# 2$ 2% 2^ Identifying the Circuitry on the PA PCBs b RF output low pass filter/directional coupler PCB directional coupler c 2^ low pass filter control PCB d power supply ambient air temperature PCB 2% e 28VDC power feed 60W PCB microprocessor f 6W PCB temperature sense 6W driver transistor drain current sense 2$ I2C signal filtering g RF input (obscured) 28VDC input 2# h 6W PCB pre-driver transistor 2@ 6W driver transistor i termination resistor (50Ω load) splitter PCB 2! j 60W PCB temperature sense 60W final transistor 60W PCB 2) 1) 60W final transistor drain current sense 1( combiner PCB termination resistor (50Ω load) 1* Note: This drawing shows a 100W UHF (H band) PA. The configuration of the 5W and 50W PAs is shown in Figure 5.1 on page 79. 1& 1@ 1# 1^ 1% TB8100 Service Manual © Tait Electronics Ltd April 2004 1! 1$ Power Amplifier Circuit Description 75 76 Power Amplifier Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 5 Power Amplifier Servicing Caution The termination resistors used in the 100W power amplifier contain some beryllium oxide. This substance is perfectly harmless in its normal solid form, but can become a severe health hazard when it has been reduced to dust. For this reason the termination resistors should not be broken open, mutilated, filed, machined, or physically damaged in any way that can produce dust particles. You should safely dispose of all used or obsolete components according to your local regulations. Caution Touching high-power RF components or circuits can cause serious burns. We strongly recommend you do not touch any RF components or tracks in the PA while it is transmitting. Caution The TB8100 power amplifier (PA) weighs between 4.8kg and 5.8kg. Take care when handling the PA to avoid personal injury. Important This equipment contains devices which are susceptible to damage from static charges. Refer to “ESD Precautions” on page 15 for more information on antistatic procedures when handling these devices. The TB8100 PA is a modular design with the circuitry divided between separate PCBs which are assembled in different configurations in different models. This chapter provides information on how to identify, remove and replace the main mechanical parts and individual PCBs. Figure 5.10 on page 97 and Figure 5.11 on page 98 identify the main mechanical parts, and Figure 5.1 on page 79 identifies the individual PCBs and shows how they are configured in different models. “Identifying the PA” on page 78 explains how to identify the model and hardware configuration of a PA from its product code. Note TB8100 Service Manual © Tait Electronics Ltd April 2004 Unless otherwise noted, the instructions and illustrations in this chapter refer to a 100W UHF (H band) PA. However, the same basic procedures and techniques apply to other models of PA. Power Amplifier Servicing 77 5.1 Disassembly and Reassembly Identifying the PA You can identify the model and hardware configuration of a PA by referring to the product code printed on labels on the heatsink and rear of the cover. The meaning of each character in the product code is explained in the table below. Note This explanation of PA product codes is not intended to suggest that any combination of features is necessarily available in any one PA. Consult your nearest Tait Dealer or Customer Service Organisation for more information regarding the availability of specific models and options. Product Code Description TBAXXXX-XXXX 7 = 5W 8 = 50W 9 = 100W TBAXXXX-XXXX 0 = default TBAXXXX-XXXX Frequency Band and Sub-band B1 = 136MHz to 174MHz C0 = 174MHz to 225MHz H0 = 400MHz to 520MHz K2 = 762MHz to 870MHza TBAXXXX-XXXX 0 = default TBAXXXX-XXXX 0 = default TBAXXXX-XXXX 0 = default TBAXXXX-XXXX 0 = default a. The actual frequency coverage in this band is 762MHz to 776MHz, and 850MHz to 870MHz. 78 Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 5.1 Identifying the PA PCBs 5W PA b g d under shield e f 50W PA b h c d under shield e f 100W PA j c b i c d e f b c d e f 6W PCB 60W PCB low pass filter/directional coupler PCB control PCB g h i j 5W interconnect PCB 50W interconnect PCB splitter PCB combiner PCB ambient air temperature sensor PCB TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Servicing 79 Screw Torque Settings The recommended torque settings for the screws used in the PA are as follows: Location / Function Torque Driver Size secure the RF power transistors to the heatsink 0.6N·m / 5.0lbf·in 3/32in Allen key 4–40 UNC secure the SMA connector to the front panel 0.3N·m / 2.5lbf·in T8 M2.5 M3 screws are used in all other locations 0.5N·m / 4.5lbf·in T10 M3 Removing the Airflow Duct and Cover The circled numbers in the following instructions refer to Figure 5.2. Airflow Duct (100W PA Only) Cover 1. Remove the M3 Torx screw b securing the P-clip and DC input cable to the airflow duct. 2. Remove the M3 Torx screws c securing the airflow duct to the heatsink. Lift the airflow duct off the heatsink. 1. Remove the M3 Torx screws securing the cover to the heatsink and to the front panel. 2. Remove the two M3 Torx screws securing the N-type connector to the cover d. 3. Carefully lift the cover straight up off the heatsink, being careful not to put any strain on the N-type connector. Removing the Front Panel The circled numbers in the following instructions refer to Figure 5.2. 80 1. Disconnect the +28VDC power feed by desoldering the feedthrough capacitor from the metal strap e soldered to the 6W PCB. 2. Remove the four M2.5 Torx screws f securing the SMA connector to the heatsink and to the front panel. 3. Desolder the centre pin of the SMA connector g from the 6W PCB and remove the connector. 4. Remove the M3 Torx screws securing the front panel to the heatsink and remove the panel. Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 5.2 Removing the Airflow Duct, Cover and Front Panel b c x3 on other side d f x4 e g TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Servicing 81 Refitting the Front Panel The circled numbers in the following instructions refer to Figure 5.2 on page 81. 1. Refit the front panel and secure it to the heatsink with the M3 Torx screws. 2. Insert the SMA connector through the front panel and secure it to the heatsink and front panel with the four M2.5 Torx screws f . 3. Resolder the centre pin of the SMA connector g to the 6W PCB. 4. Resolder the +28VDC feedthrough capacitor to the metal strap e soldered to the 6W PCB. Refitting the Cover and Airflow Duct The circled numbers in the following instructions refer to Figure 5.2 on page 81. Cover 1. Slide the cover into place on the heatsink. Make sure the cover is seated correctly between the heatsink and N-type connector. 2. Secure the cover with the M3 Torx screws. Fit the two screws d securing the N-type connector to the cover first, followed by the screws securing the cover to the heatsink. Note Airflow Duct (100W PA Only) 82 1. Slide the airflow duct into place on the heatsink and secure with the M3 Torx screws. 2. Secure the DC input cable to the airflow duct with the P-clip and M3 Torx screw b. Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 5.2 PCB Connecting Links There are two types of link used to connect individual PCBs in the PA: ■ RF links b are used to carry RF signals from one PCB to another ■ bridging links c are used to carry control signals from one PCB to another. Figure 5.3 shows typical examples of both types of links. Figure 5.3 PCB Connecting Links c 5.3 b Replacing the 6W PCB Important There is heatsink compound between the PCB and the heatsink under certain components. Any objects caught in the heatsink compound underneath the PCB which prevent effective heatsinking may cause these components to fail. Important If you replace the 6W PCB, you must recalibrate the PA bias using the Calibration Kit software. Refer to the Calibration Kit documentation for more details. Refer to Section 5.1 “Disassembly and Reassembly” for details on removing and refitting the cover and front panel. The circled numbers in the following instructions refer to Figure 5.4 on page 84. Figure 5.4 shows a 50W UHF (H band) PA. The exact number and location of links may differ in other models. Removal 1. Remove the cover and front panel. 2. Remove the bridging links b connecting the PCB to the control PCB. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Servicing 83 Refitting 3. If necessary, desolder the +28VDC power feed wire c. 4. Desolder the RF links d connecting the PCB to any adjacent PCBs. 5. Remove the M3 Torx screws securing the PCB to the heatsink. 6. Carefully lift the PCB directly upwards off the locating pins e and remove it from the heatsink. 1. Ensure the heatsink and bottom of the PCB are clean. Remove any old heatsink compound. 2. Apply a thin layer of fresh heatsink compound to the bottom of the PCB underneath Q103 f, D200 g and AT100 h (if fitted). Use as little as possible, while still covering the whole of the mounting area of each component. 3. Refit the PCB, following the removal instructions in reverse order. Note 4. Before tightening the screws, press the PCB down over the locating pins so that it is firmly seated against the heatsink. Then tighten the M3 Torx screws to the correct torque. Refit the front panel and cover. Figure 5.4 Replacing the 6W PCB e h f g c e d b 84 Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 5.4 Replacing the 60W PCB Important There is heatsink compound between the RF power transistor and the heatsink. You may need to carefully prise the transistor away from the heatsink with a small screwdriver. Any objects caught in the heatsink compound underneath the transistor which prevent effective grounding and/or heatsinking may cause the transistor to fail. Important If you replace the 60W PCB, you must recalibrate the PA bias using the Calibration Kit software. Refer to the Calibration Kit documentation for more details. Refer to Section 5.1 “Disassembly and Reassembly” for details on removing and refitting the cover. The circled numbers in the following instructions refer to Figure 5.5 on page 86. Removal Refitting the Same PCB and Transistor 1. Remove the cover. 2. Remove the bridging links b connecting the PCB to the control PCB. 3. Desolder the +28VDC power feed wire c. 4. Desolder the RF links d connecting the PCB to any adjacent PCBs. 5. Remove the 4-40 UNC Allen screws e securing the RF power transistor f to the heatsink. 6. Remove the M3 Torx screws securing the PCB to the heatsink. 7. Carefully lift the PCB directly upwards off the locating pins g and remove it from the heatsink. Use the following instructions if you are fitting the same 60W PCB and RF power transistor, and haven’t disturbed any of the solder joints around the transistor. 1. Ensure the heatsink and bottom of the transistor are clean. Remove any old heatsink compound. 2. Apply a thin layer of fresh heatsink compound to the bottom of the transistor. Use as little as possible, while still covering the whole of the mounting area of the transistor. 3. Refit the PCB, following the removal instructions in reverse order. Note TB8100 Service Manual © Tait Electronics Ltd April 2004 Before tightening the screws, press the PCB down over the locating pins so that it is firmly seated against the heatsink. Then tighten the M3 Torx screws to the correct torque. Power Amplifier Servicing 85 Refitting a New PCB and Transistor 4. Progressively tighten each 4–40 UNC screw, alternating from side to side, to the correct torque. Retorque the screws after eight hours of operation. 5. Refit the cover. Use the following instructions if you are fitting a new 60W PCB, a new RF power transistor, or have disturbed any of the solder joints around the transistor. 1. Remove any old heatsink compound from the heatsink. 2. Refit the PCB, following the removal instructions in reverse order. Note Figure 5.5 Before tightening the screws, press the PCB down over the locating pins so that it is firmly seated against the heatsink. Then tighten the M3 Torx screws to the correct torque. 3. Fit the new RF power transistor as described in the “Refitting” section of “Replacing the 60W RF Power Transistor” on page 87. 4. Refit the cover. Replacing the 60W PCB d g d f b e g d c 86 Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 5.5 Replacing the 60W RF Power Transistor Important If you do not follow these procedures correctly, the transistor may fail because of poor heatsinking. Important Do not apply too much heat or pressure to the PCB pads and tracks as you may damage them or lift them from the PCB. This will permanently damage the PA. Important Insulated gate FET transistors are susceptible to damage from static charges, due to their extremely high input resistance. To avoid possible damage to the device during handling, testing or actual operation, we recommend you follow these procedures: avoid unnecessary handling; when handling the device, pick it up by the cap, not the leads; do not insert or remove the device while the power is on; avoid contact with non-conductive plastic or non-conductive styrofoam. Important If you replace an RF power transistor, you must recalibrate the PA bias using the Calibration Kit software. Refer to the Calibration Kit documentation for more details. Refer to Section 5.1 “Disassembly and Reassembly” for details on removing and refitting the cover. The circled numbers in the following instructions refer to Figure 5.6 on page 88. Removal Refitting 1. Remove the cover. 2. Remove the two 4–40 UNC Allen recess head screws b securing the transistor to the heatsink. 3. Desolder and remove the two ground tags c. 4. Desolder the transistor tabs d by heating them with a soldering iron and then carefully lifting them away from the PCB with a screwdriver or thin stainless steel spike. When the tabs are completely free of the PCB, remove the transistor. 5. Remove any excess solder from the PCB pads with solder wick. 6. Remove any old heatsink compound from the heatsink. 1. Lightly tin the underside of the transistor tabs. Remove any excess solder to leave a thin, even layer of solder on the tabs. 2. Apply a small amount of heatsink compound (Dow-Corning 340 or equivalent) to the transistor mounting surface. Use as little as possible TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Servicing 87 to provide a very thin, but even, film over the entire mounting surface. 3. Place the transistor on the PCB in the correct orientation and ensure the tabs are flush with the surface. Important 4. Refit the two ground tags and secure the transistor to the heatsink with the two 4–40 UNC screws. Progressively tighten each screw, alternating from side to side, to the correct torque. 5. Solder the ground tags and transistor tabs to the PCB. While soldering the transistor tabs, gently press down on them with a ceramic trimming tool to ensure they are as close as possible to the pads on the PCB. 6. Retorque the 4–40 UNC screws after eight hours of operation. 7. Refit the cover. Figure 5.6 b 88 Make sure the heatsink compound is clean. Any objects caught in the heatsink compound underneath the transistor which prevent effective heatsinking may cause the transistor to fail. Power Amplifier Servicing Replacing the 60W RF Power Transistor d d c TB8100 Service Manual © Tait Electronics Ltd April 2004 5.6 Replacing the Control PCB Important You must reprogram and recalibrate the PA after replacing the control PCB. Refer to “Reprogramming and Recalibration” on page 90. Refer to Section 5.1 “Disassembly and Reassembly” for details on removing and refitting the cover and front panel. The circled numbers in the following instructions refer to Figure 5.7 on page 90. Removal Refitting 1. Remove the cover and front panel. 2. Remove the ambient air temperature sensor PCB b. 3. Remove the bridging links c connecting the PCB to any adjacent PCBs. 4. Desolder the RF links d connecting the PCB to any adjacent PCBs. You may need to move the +28V power feed wire e out of the way first. 5. Remove the M3 Torx screws securing the PCB to the heatsink. 6. Carefully lift the PCB directly upwards off the locating pins f and remove it from the heatsink. 1. To refit the PCB, follow the removal instructions in reverse order. Important Note TB8100 Service Manual © Tait Electronics Ltd April 2004 When refitting the ambient air temperature sensor PCB, make sure that it fits properly into the correct hole provided in the heatsink (refer to Figure 5.7). You must fit the sensor PCB in the correct location to ensure that the temperature of the airflow over the sensor is nearest the ambient temperature of the air at the intake to the cooling fan. The sensor PCB must not come into contact with the metal of the heatsink fins. Note that you may feel some resistance as you push the sensor PCB through the slot in the foam dust seal located under the control PCB. Before tightening the screws, press the PCB down over the locating pins so that it is firmly seated against the heatsink. Then tighten the M3 Torx screws to the correct torque. Power Amplifier Servicing 89 Figure 5.7 c Replacing the Control PCB d b 5/50W PA Reprogramming and Recalibration d f e c d f If you have replaced the control PCB, you will have to reprogram and recalibrate the PA as described in the table below. Procedure ■ reprogram the product code ■ reprogram the PA type replace the serial number labels 90 b 100W PA ■ calibrate the stage bias ■ calibrate the forward and reverse detector bias voltages ■ calibrate the PA output power Power Amplifier Servicing Details reprogram this information into the PA using the Calibration Kit software; refer to the Calibration Kit documentation for more details the serial number of the PA will change to the number already programmed into the replacement control PCB; stick the new serial number labels onto the heatsink and rear panel carry out these procedures using the Calibration Kit software; refer to the Calibration Kit documentation for more details TB8100 Service Manual © Tait Electronics Ltd April 2004 5.7 Replacing the Low Pass Filter/Directional Coupler PCB Important If you replace the LPF/directional coupler PCB, you must recalibrate the detector bias voltages and PA output power using the Calibration Kit software. Refer to the Calibration Kit documentation for more details. Refer to Section 5.1 “Disassembly and Reassembly” for details on removing and refitting the cover. The circled numbers in the following instructions refer to Figure 5.8 on page 92. Removal Refitting 1. Remove the cover. 2. Desolder the two tabs and remove the shield lid. 3. Remove the bridging links b connecting the PCB to the control PCB. 4. Desolder the RF links c connecting the PCB to any adjacent PCBs. 5. Remove the M3 Torx screws securing the N-type connector to the heatsink. 6. Desolder and remove the N-type connector, leaving the ground plate d soldered in place on the shield wall. 7. Remove the M3 Torx screws securing the PCB to the heatsink. 8. Carefully lift the PCB directly upwards off the locating pins e and remove it from the heatsink. 1. Refit the PCB onto the heatsink, ensuring it is correctly positioned on the locating pins. 2. Secure the PCB to the heatsink with the M3 Torx screws and tighten to the correct torque. 3. If the ground plate d is already soldered to the shield wall: ■ fit the N-type connector and tighten the two M3 Torx screws to the correct torque ■ solder the N-type connector to the PCB. If the ground plate is not already soldered to the shield wall: TB8100 Service Manual © Tait Electronics Ltd April 2004 ■ fit the ground plate and N-type connector to the heatsink, ensuring that the tab on the ground plate fits through the slot in the shield wall ■ tighten the two M3 Torx screws to the correct torque ■ solder the N-type connector to the PCB ■ solder the tag on the ground plate to the inside of the shield wall. Power Amplifier Servicing 91 Note In both cases make sure that the ground plate sits flat against the base of the N-type connector, otherwise the cover may not fit correctly. 4. Replace the RF links c and bridging links b. 5. Refit the shield lid and resolder the two tabs. 6. Refit the cover. If you are fitting a new PCB, make sure that the RF input tab f is left in place for a 5W or 50W PA, and removed for a 100W PA. If you have to remove the tab, cut it off cleanly with a sharp cutting tool (such as tin snips or a guillotine). Note Figure 5.8 Replacing the LPF/Directional Coupler PCB 100W PA 5W and 50 W PA f e c d b 5.8 Replacing the Interconnect PCBs Refer to Section 5.1 “Disassembly and Reassembly” for details on removing and refitting the cover. Removal 92 1. Remove the cover. 2. Desolder the RF links connecting the PCB to any adjacent PCBs. You may need to move the +28VDC power feed wire out of the way first. 3. Remove the M3 Torx screws securing the PCB to the heatsink. Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Refitting 4. Carefully lift the PCB directly upwards off the locating pins and remove it from the heatsink. 1. To refit the PCB, follow the removal instructions in reverse order. Note 5.9 Before tightening the screws, press the PCB down over the locating pins so that it is firmly seated against the heatsink. Then tighten the M3 Torx screws to the correct torque. Replacing the Splitter/Combiner PCBs Important There is heatsink compound between the termination resistors and the heatsink. You may need to carefully prise the resistors away from the heatsink with a small screwdriver. Any objects caught in the heatsink compound underneath the resistors which prevent effective grounding and/or heatsinking may cause the resistors to fail. There is also heatsink compound between the PCB and the heatsink under the splitter and combiner devices. Any objects caught in the heatsink compound underneath the PCB which prevent effective heatsinking may cause these components to fail. Important Do not apply too much heat or pressure to the PCB pads and tracks as you may damage them or lift them from the PCB. This will permanently damage the PA. Refer to Section 5.1 “Disassembly and Reassembly” for details on removing and refitting the cover. The circled numbers in the following instructions refer to Figure 5.9 on page 94. Removal 1. Remove the cover. 2. Desolder the RF links b connecting the PCB to any adjacent PCBs. 3. Desolder the tab of the termination resistor c and carefully lift it away from the PCB with a screwdriver or thin stainless steel spike. 4. Desolder the termination resistor ground tag(s) d and carefully lift away from the PCB with a screwdriver or thin stainless steel spike. 5. Remove the 4-40 UNC Allen screw(s) e securing the termination resistor to the heatsink and carefully remove the resistor and ground tag(s). 6. Remove the M3 Torx screws securing the PCB to the heatsink. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Servicing 93 7. Figure 5.9 Carefully lift the PCB directly upwards off the locating pins f and remove it from the heatsink. Replacing the Splitter/Combiner PCBs Splitter Combiner e f d b c b b f d b d Refitting 94 e c e 1. Ensure the heatsink and bottom of the PCB are clean. Remove any old heatsink compound. 2. Apply a thin layer of fresh heatsink compound (Dow-Corning 340 or equivalent) to the bottom of the PCB underneath the splitter or combiner. Use as little as possible, while still covering the whole of the mounting area of the component. 3. Refit the PCB onto the heatsink, ensuring it is correctly positioned on the locating pins. 4. Secure the PCB to the heatsink with the M3 Torx screws and tighten to the correct torque. 5. Apply a small amount of heatsink compound to the termination resistor mounting surface. Use as little as possible to provide a very thin, but even, film over the entire mounting surface. 6. Place the resistor on the heatsink and ensure the tab is flush with the surface of the PCB. Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Important Make sure the heatsink compound is clean. Any objects caught in the heatsink compound underneath the resistor which prevent effective heatsinking may cause it to fail. 7. Refit the ground tag(s) and secure the resistor to the heatsink with the 4–40 UNC screw(s). If there are two screws, progressively tighten each screw, alternating from side to side, to the correct torque. 8. Solder the ground tag(s) and resistor tab to the PCB. While soldering the resistor tabs, gently press down on them with a ceramic trimming tool to ensure they are as close as possible to the pads on the PCB. 9. Retorque the 4–40 UNC screws after eight hours of operation. 10. Refit the cover. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Amplifier Servicing 95 96 Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 5.10 PA Mechanical Assembly - Sheet 1 Description IPN b c d DC input feedthrough capacitor 012-04100-07 DC power link 051-00640-XX DC input cable - 5/50W DC input cable - 100W 219-02854-XX 219-02855-XX e f g h i j bridging links 240-00020-61 N-type connector 240-02100-64 SMA connector 240-02155-20 P-clip 303-50107-XX handle 308-01065-XX heatsink - 5/50W heatsink - 100W 308-13144-XX 308-13145-XX 1) front panel - 5/50W front panel - 100W 316-06815-XX 316-06817-XX 1! 1@ 1# 1$ 1% 1^ 1& 1* 1( 2) 2! 2@ 2# 2$ 2% 2^ LPF/directional coupler shield lid 319-01247-XX N-type connector ground plate 319-01249-XX LPF/directional coupler shield lid spring contacts 319-01259-XX M3x6mm countersunk Torx screw 345-40460-XX M3x8mm pan head Torx screw + spring/flat washers 345-40470-XX M2.5x8mm pan head Torx screw 345-40490-XX M3x10mm pan head Torx Taptite screw 349-02066-XX 4–40x5/16 UNC Allen recess head screw 349-20460-XX 3mm solder tag - short 356-00010-01 3mm solder tag - long 356-00010-03 4mm right-angle solder tag 356-00010-74 RF link 356-01080-XX ground tag for 60W RF power transistor 356-01081-XX metal strap for feedthrough capacitor 356-01082-XX insulating washer for feedthrough capacitor 362-00010-51 dust seal for ambient air temperature sensor PCB 362-01036-XX 2& 2* 2( 3) 3! 3@ 3# 3$ control PCB 6W PCB Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. 3! 2@ 3@ 1# 1* x2 c Note: This drawing shows a 100W PA. Any differences between the 100W, 5W and 50W PAs are indicated in the description of the parts. 1! 2# x2 1*1( x2 2( 3) 1* e 1( 1% 2& 3) 2* 3$ 2) x2 2$ 3# 1% x4 2^ g x2 f 1^ x4 1@ d LPF/directional coupler PCB j 60W PCB ambient air temperature sensor PCB combiner PCB splitter PCB h 1$ x3 each side bridging link PCB 50W interconnect PCB* 5W interconnect PCB* *Not shown in this drawing. Refer to Figure 5.1 on page 79. TB8100 Service Manual © Tait Electronics Ltd April 2004 1& 1) 1& x2 i 2% b 2! 1$ x5x4 100W 5/50W Power Amplifier Servicing 97 Figure 5.11 PA Mechanical Assembly - Sheet 2 Description IPN b cover - 5/50W cover - 100W 303-03070-XX 303-03071-XX c d e f g P-clip 303-50107-XX airflow duct centre panel 316-06818-XX airflow duct side panel 316-06819-XX M3x6mm countersunk Torx screw 345-40460-XX M3x10mm pan head Torx Taptite screw 349-02066-XX b Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. 100W f x26 x24 5/50W e d c e g f x3 each side 98 Power Amplifier Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 6 Power Management Unit Circuit Description The TB8100 power management unit (PMU) provides stable, low-noise 28VDC outputs to power the TB8100 BSS. The PMU is made up of a number of individual PCBs and cards which comprise two main modules, the AC module and the DC module. The standby power supply card and auxiliary power supply PCB are optional. The AC module accepts an input of 115/230VAC 50/60Hz nominal, and the DC module accepts an input of 12, 24 or 48VDC1 nominal (depending on the model). Both modules provide the following outputs: ■ 28VDC high current (PA) ■ 28VDC low current (reciter) ■ 13.65, 27.3 or 54.6VDC low current (with the optional auxiliary power supply PCB). The PMU is available in three main configurations: ■ AC PMU (AC input only) ■ DC PMU (DC input only) ■ AC and DC PMU (both the AC and DC modules are fitted to allow both AC and DC inputs). If both the AC and DC modules are fitted, the PMU uses the AC input by default, and provides battery back-up by operating from the DC input if the AC input is interrupted. The changeover from AC to DC input, and from DC back to AC input, is breakless. This allows the base station to operate without interruption. The optional standby power supply card allows efficient use of the DC input at low power requirements. The optional auxiliary power supply PCB provides output voltages which are different from the 28VDC required by the TB8100 BSS. It can also be used to trickle-charge batteries. Figure 6.1 on page 100 shows the configuration for an AC and DC PMU, along with the main inputs and outputs for power and control signals. The table which follows shows which PCBs and cards are fitted in each module. The locations of the main circuit blocks on the PCBs are shown in Figure 6.5 on page 109 and Figure 6.6 on page 111. 1. Because the DC module is designed to run from a battery, there will be a minimum start-up voltage when operating on DC only (refer to the TB8100 Specifications Manual for more details). TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Circuit Description 99 Figure 6.1 PMU High Level Block Diagram AC Module AC I/P 115/230V 50/60Hz AC Converter PCB 28V O/P (PA) 28V O/P (Reciter) PFC 400VDC Circuitry PFC Control Card HVDC Circuitry 28V System Control Bus HVDC Control & Microprocessor Card DC Module DC DC I/P I/P 12/24/48V 12V DC Input Filter Card Battery Control Card Standby Power Supply Card* Auxiliary Power Supply PCB* 28V 28V DC Converter PCB DC O/P 13.65/27.3/54.6V 13.8V O/P DC Control Card *optional 100 Power Management Unit Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 PCB and Card Name AC PMU DC PMU AC and DC PMU DC converter PCB fitted fitted DC input filter card fitted fitted DC control card fitted fitted battery control card fitted fitted standby power supply carda optional optional AC converter PCB fitted fittedb fitted HVDC control and microprocessor card fitted fittedc fitted PFC control card fitted auxiliary power supply PCBd optional fitted optional optional a. You must fit the appropriate model card to match the DC input voltage of the PMU (i.e. 12, 24 or 48VDC nominal). b. Only the current sense and output filter circuitry is placed on this PCB when it is fitted to a DC PMU. c. Only the feedback and microprocessor circuitry is placed on this card when it is fitted to a DC PMU. d. The output voltage is dependent on the model of PCB - there is a different model PCB for each output voltage (i.e. 13.65, 27.3 or 54.6VDC). 6.1 Microprocessor Control Circuitry The microprocessor on the HVDC control card monitors and controls the operation of the PMU. If any of the monitored conditions exceeds its normal range of values, the microprocessor will generate an alarm and take appropriate action, depending on the configuration of the PMU. The software also automatically detects the PMU configuration and controls the PMU accordingly. The alarms and diagnostic functions are accessed through I2C bus messages on the system control bus via the reciter, control panel and Service Kit software. The microprocessor also calibrates the output voltage to the required specification. This information is stored in EEPROM memory during factory run-up. The output voltage of an uncalibrated PMU is 26.5VDC. Figure 6.2 on page 102 shows the control signal and power connections to and from the microprocessor. These are described in more detail in the paragraphs which follow. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Circuit Description 101 Figure 6.2 PMU Microprocessor Functional Block Diagram Microprocessor Supply Fan Output 5V Supply R Fan Current Sense Data Auxiliary Power Supply* Run Voltage Sense Flash Programming Supply Vpp Auxiliary Output Current Sense Temperature Mains OK Shutdown I2C Signals Summary Alarm Output Summary Alarm On Microprocessor I2C Port Vpp Enable Fan Supply On V 0V Standby Supply Isolate Data Hysteresis Mode DC Converter Run 0V Battery Input Low Battery Alarm On 28V I Mains Input Temperature Low Battery Alarm Output AC Converter On/Off Battery Supply Reciter Output Standby Supply Present Shutdown Standby Power Supply* 0V *optional AC Converter The microprocessor can enable or disable the AC converter if the user needs to test the DC module and battery back-up by simulating a failure of the AC mains input. The microprocessor monitors the output voltage and current, the temperature of the AC module heatsink, and whether the AC mains input is within the specified range. DC Converter The microprocessor controls the on/off function of the DC converter. It also controls the mode of operation of the DC converter: normal mode, hysteresis mode1, or deep sleep mode. Refer to “Hysteresis Mode” on page 107 for details on hysteresis mode, and to “Standby Power Supply” below for details on deep sleep mode. 1. A type of “sleep” mode available when the standby power supply card is not fitted. 102 PA Output Power Management Unit Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 The microprocessor monitors the battery input voltage and the temperature of the DC module heatsink. It also identifies the model of DC converter fitted to the DC module (i.e 12, 24 or 48V nominal input). Standby Power Supply The microprocessor detects whether this power supply is fitted, and disables it when the AC mains supply is operating. The output from this power supply can be isolated from the reciter output to maintain power to the microprocessor when battery capacity is low. The low battery threshold is set with the Service Kit software. This power supply is also used to maintain power to the microprocessor when the PMU is in deep sleep mode and the DC converter is switched off. Deep sleep mode is configured with the Service Kit software and can only function if the load on the PMU reciter output is <10W. If the power supply is not fitted, the microprocessor is powered by an internal 5V power supply derived from the main PA output. Auxiliary Power Supply The microprocessor controls the on/off function for this power supply. The actual operation of the power supply is set with the Service Kit software: ■ on only when AC mains is present ■ controlled by Task Manager. The microprocessor detects when the power supply is operating. It also detects which model of power supply is fitted (12, 24 or 48V), whether the power supply is operating or not. Front Panel Fan The microprocessor measures the current drawn by the PMU fan mounted in the front panel. It protects the fan driver circuitry from overload or short circuit by switching the fan off for five seconds, and then switching it on again. The microprocessor will continue to try running the fan indefinitely. If the fan has failed, the reciter sends an alarm to the Service Kit. I2C Communications The microprocessor controls the I2C communications between the PMU and the base station system. The current source used by the I2C lines as active pull-up resistors is housed on the microprocessor PCB. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Circuit Description 103 6.2 AC Module The AC module accepts an input of 115/230VAC 50/60Hz nominal, and provides two regulated 28VDC outputs: high current for the PA, and low current for the reciter. The main circuit blocks are shown in Figure 6.3 below, and are described in more detail in the paragraphs which follow. Figure 6.3 AC I/P 115/230V 50/60Hz PMU AC Module Block Diagram 28VDC O/P (PA) EMC Filter, Protection, & AC Switch Power Factor Correction (PFC) High Voltage to DC (HVDC) Current Sense and Output Filter 28VDC O/P (Reciter) PFC Control HVDC Control DC Interface to DC Module Microprocessor Control & Monitor EMC Filter, Protection, and AC Switch System Interface and Fan Control System Control Bus Fan The AC input is fed first to an EMC filter consisting of two common-mode and two differential-mode filters. The input voltage is monitored, and if it is within the specified voltage range, a “mains OK” signal is sent to the microprocessor via an opto-coupler. If the mains input voltage is outside the specified range, the power factor stage is inhibited to protect the AC converter from damage. An MOV is fitted between line and phase to clamp low energy noise on the line. A 10A fuse is also fitted for additional safety. If the fuse blows, it disconnects the PMU from the mains. Inrush current control is provided by a high power resistor, which is bypassed by a relay when the PMU is powered up. Power Factor Correction (PFC) The filtered AC input is fed to this boost power supply where the active power factor correction circuit converts it to the regulated 400VDC output. This stage is fully protected from overload and short circuit by the power supply control circuitry. PFC Control The control circuitry for the boost power supply is located on the PFC control card which plugs into the AC converter PCB. This circuitry is designed to achieve a power factor of near unity. The power supply for the 104 Power Management Unit Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 PFC control circuitry is derived from the secondary winding on the main boost choke. High Voltage to DC (HVDC) The regulated 400VDC from the PFC circuitry is converted to a regulated 28VDC output using a forward converter. The forward converter transformer provides galvanic isolation between the input and output. The primary is switched between 400V and 0V via two power MOSFETs. The output from the transformer is rectified and filtered before being fed to a current sense resistor. HVDC Control This secondary control circuitry consists of a voltage and current amplifier, which provides a combined error signal. This error signal is fed via an optocoupler to the PWM (pulse width modulation) controller IC, which is part of the primary control circuitry. The power supply for the HVDC control circuitry is derived from the secondary winding on the main transformer. The HVDC control circuitry is located on a separate card which plugs into the AC converter PCB. Current Sense and Output Filter The current sense resistor provides the current output level to the microprocessor for monitoring purposes and to supply data to the Service Kit software. The current output level is also used by the analogue current control loop to limit the maximum output current. After the current shunt the regulated 28VDC output is split and filtered to provide two DC outputs: a high current output for the PA, and a low current output for the reciter. The high current output is electronically protected, and the low current output is protected by a 2.5A self-resetting fuse. The low current output for the reciter is normally supplied by the standby power supply. If this card is not fitted, the high current PA output is also supplied to the low current reciter output via a diode. The current sense and output filter circuitry is also used by the DC converter to provide a common output stage for the PMU. Microprocessor Control The microprocessor is located on the HVDC control card and is referenced to the output (secondary side) of the converter. The microprocessor is used by both the AC and DC modules and is fitted to all PMU models. The microprocessor controls the output voltage to the fan via a MOSFET and dropping resistor to provide the 24VDC output. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Circuit Description 105 System Interface and Fan Control The system interface circuitry consists of the I2C lines, fan power, and alarm outputs, which are fed to the system control bus connector on the front panel. There is high frequency filtering on all lines. The microprocessor also monitors the current drawn by the PMU fan and protects it from overload or short circuit. Interface to DC Module 6.3 This interface consists of the connectors which connect the AC module to the DC module. Although there is no circuitry involved this interface, it is included in the block diagram to illustrate the interconnection between the AC and DC modules. DC Module The DC module accepts an input of 12, 24 or 48VDC nominal, and provides two regulated 28VDC outputs: high current for the PA, and low current for the reciter. The main circuit blocks are shown in Figure 6.4 below, and are described in more detail in the paragraphs which follow. Figure 6.4 DC I/P 12/24/48V PMU DC Module Block Diagram EMC Filter and Protection DC Power Converter (DCDC) Control & Monitor DC Control Interface to AC Module DC Battery Control Standby Power Supply* Auxiliary Power Supply* DC O/P 13.65/27.3/54.6V *optional 106 Power Management Unit Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 EMC Filter and Protection The DC input is fed first to an EMC filter consisting of bus bars, an e-core transformer, and capacitors. These components are located on the DC input filter card, which is connected to the DC converter PCB via the bus bars and soldered tabs. The protection is provided by an anti-parallel diode, which prevents damage from reverse polarity input voltage. External series protection (e.g. fuse or circuit breaker) must be provided by the user. DC Power Converter (DCDC) In this stage the filtered DC input is fed to a push-pull converter which converts the DC input voltage to a regulated DC output voltage. The DC voltage is fed to a high frequency transformer which provides galvanic isolation between input and output via two pairs of power MOSFETS on the primary winding. The output from this transformer is rectified and filtered before being fed to the current sense and output filter circuitry on the AC converter PCB. DC Control This secondary control circuitry consists of a voltage amplifier, which provides a reference voltage and error signal. This error signal is fed via an opto-coupler to the PWM controller IC, which is part of the primary control circuitry. The power supply for the DC control circuitry is provided by the battery control card. The DC control circuitry is located on a separate card which plugs into the DC converter PCB. Hysteresis Mode When the DC control circuitry receives a “hysteresis enable” signal from the microprocessor, it changes the regulation to a hysteric method (hysteresis mode). Hysteresis mode is used in sleep mode to improve the efficiency of the DC converter under light loads. Sleep mode is configured with the Service Kit software and can only function if the load on the PMU is <10W. In hysteresis mode the DC converter is switched off when the output voltage reaches the maximum threshold, and on again when the voltage reaches the minimum threshold. The thresholds are set in hardware at the factory. While the DC converter is switched on, the output capacitors are charged. When the DC converter is switched off, the output capacitors are discharged by the load connected to the PMU. The discharge time varies in proportion to the load. The longer the discharge time, the greater the efficiency of the PMU, as less power is drawn from the battery. Battery Control The battery control circuitry monitors the DC input voltage from the battery. If the voltage is within the specified range, power is supplied to the control circuitry and optional standby power supply (if fitted). Protection is provided against the wrong input voltage being supplied. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Circuit Description 107 The battery input voltage is also provided as a digital signal to the microprocessor via opto-coupler circuitry. This provides isolation between battery ground and microprocessor ground. The battery control circuitry also prevents deep discharge of the battery by removing the load from the battery if the voltage falls below a minimum threshold. This threshold is independent of the microprocessor threshold, which is set by the user with the Service Kit software. Another function of the battery control circuitry is to provide the microprocessor with information to identify which DC module is fitted to the PMU (i.e. 12, 24 or 48V). The battery control circuitry is located on a separate card which plugs into the DC converter PCB. Standby Power Supply The optional standby power supply is a high efficiency, low power DC converter which operates in parallel with the main DC converter. This converter provides a low power output to the reciter, and can also operate when the main DC converter is shut down (i.e. deep sleep mode). It is protected from overload and short circuit. The circuitry for the standby power supply is located on a separate card which plugs into the DC converter PCB. Auxiliary Power Supply The optional auxiliary power supply uses a high power version of the circuit design used in the standby power supply. It operates from the AC power supplied to the PMU. The mode of operation is controlled with the Service Kit software. The circuitry for the auxiliary power supply is located on a separate PCB which is mounted on the heatsink of the DC module. The PCB is connected to the AC converter PCB via an 8-way cable. The main function of this power supply is to provide a controlled 13.65, 27.3 or 54.6VDC output (depending on model), as the main output for the TB8100 base station system is 28VDC. However, because the converter is voltage and current regulated, it can also be used to trickle-charge batteries. The output voltage is set in the factory to the required float voltage, so the batteries can remain connected at all times. Interface to AC Module 108 This interface consists of the connectors which connect the DC module to the AC module. Although there is no circuitry involved this interface, it is included in the block diagram to illustrate the interconnection between the DC and AC modules. Power Management Unit Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 6.5 b c d e f g h i j 1) 1! 1@ 1# 1$ Identifying the Circuitry on the AC Module PCBs EMC filter, protection and AC switch power factor correction (PFC) PFC control b 1$ high voltage to DC converter 28VDC input from the DC converter PCB current sense and output filter 1# c 28VDC output for PA 28VDC output for reciter 28VDC output to auxiliary power supply PCB microprocessor control 1@ d AC and DC voltage and current control HVDC control fuse (10A 250V) AC mains input Note: In order to show as much of the circuitry as possible in the photograph, the heatsinks and the components normally attached to them are not fitted, and the plug-in cards are not plugged in. 1! e f 1) g j h h i TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Circuit Description 109 110 Power Management Unit Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 6.6 Identifying the Circuitry on the DC Module PCBs b c d e f DC input g h i j battery control b auxiliary power supply j DC power converter DC control output to the current sense and output filter circuitry on the AC converter PCB c current transformer standby power supply i EMC filter and protection Note: In order to show as much of the circuitry as possible in the photograph, the heatsinks and the components normally attached to them are not fitted, and the plug-in cards are not plugged in. d h e g f 12V DC module shown TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Circuit Description 111 112 Power Management Unit Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 7 Power Management Unit Servicing This chapter provides information on how to identify, remove and replace the main mechanical parts, plug-in cards, and auxiliary power supply PCB. 7.1 Safety Precautions Personal Safety Warning!! The PMU contains voltages that may be lethal. Refer to the ratings label on the rear of the module. The TB8100 BSS must be installed so that the rear of the PMU is located in a service access area. Disconnect the mains IEC connector and wait for five minutes for the internal voltages to self-discharge before dismantling. The AC power on/off switch does not isolate the PMU from the mains. It breaks only the phase circuit, not the neutral. The PMU should be serviced only by qualified technicians. All servicing should be carried out only when the PMU is powered through a mains isolating transformer of sufficient rating. We strongly recommend that the mains power to the whole of the repair and test area is supplied via an earth leakage circuit breaker. Caution The magnetics and power devices attached to the heatsink in the PMU get hot when they are operating. Take care when working on a PMU that has been in recent use. Caution The PMU can weigh up to 6.4kg (14.1lb). Take care when handling the PMU to avoid personal injury. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Servicing 113 Equipment Safety Important This equipment contains devices which are susceptible to damage from static charges. Refer to “ESD Precautions” on page 15 for more information on antistatic procedures when handling these devices. Important Insulated gate FET transistors are susceptible to damage from static charges, due to their extremely high input resistance. To avoid possible damage to the device during handling, testing or actual operation, we recommend you follow these procedures: avoid unnecessary handling; when handling the device, pick it up by the cap, not the leads; do not insert or remove the device while the power is on; avoid contact with non-conductive plastic or non-conductive styrofoam. Replacing Components Connected To The Mains To maintain operator safety and protection against fire, you must replace components connected to the mains supply (e.g. fuse [10A 250V], X & Y capacitors, filter chokes, etc.) and those that are critical to maintain isolation (optocouplers, transformers, etc.) only with their new, original equivalent. To maintain performance levels we strongly recommend that you apply this policy to every component that is replaced. 114 Power Management Unit Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 7.2 Disassembly and Reassembly Mechanical Overview The TB8100 PMU is made up of a number of individual PCBs and cards which comprise two main modules, the AC module and the DC module. The standby power supply card and auxiliary power supply PCB are optional. The PMU is available in three main hardware configurations: ■ AC PMU (AC input only) ■ DC PMU (DC input only) ■ AC and DC PMU (both the AC and DC modules are fitted to allow both AC and DC inputs). The table below provides an overview of the major mechanical differences between these three configurations. PMU Configuration Part/Assembly AC PMU DC PMU AC and DC PMU AC module standard module fitted AC converter PCB is mounted on standard module fitted special brackets which also cover the holes normally covered by the AC module heatsinks; only the current sense and output filter circuitry is placed on the PCB DC module not fitted standard module fitted standard module fitted shield fitted not fitted fitted front and rear panels fitted with blanking plates to cover the holes normally covered by the DC module heatsinks fitted fitted top and bottom covers fitted fitted fitted Figure 7.6 on page 129 and Figure 7.7 on page 130 identify the main mechanical parts. Figure 7.1 on page 117 identifies the individual PCBs and cards, and shows how they are configured in an AC and DC PMU. “Identifying the PMU” on page 116 explains how to identify the model and hardware configuration of a PMU from its product code. Note TB8100 Service Manual © Tait Electronics Ltd April 2004 For the sake of simplicity and clarity, the instructions and illustrations in this chapter refer to the AC and DC PMU. However, the AC PMU and DC PMU can be disassembled and reassembled using the same basic procedures and techniques. Power Management Unit Servicing 115 Identifying the PMU You can identify the model and hardware configuration of a PMU by referring to the product code printed on a label on the rear panel. The meaning of each character in the product code is explained in the table below. Note This explanation of PMU product codes is not intended to suggest that any combination of features is necessarily available in any one PMU. Consult your nearest Tait Dealer or Customer Service Organisation for more information regarding the availability of specific models and options. Product Code 116 Description TBAXXXX-XXXX 3 = PMU TBA3XXX-XXXX 0 = default TBA3XXX-XXXX 0 = AC module not fitted A = AC module fitted TBA3XXX-XXXX 0 = DC module not fitted 1 = 12V DC module fitted 2 = 24V DC module fitted 4 = 48V DC module fitted TBA3XXX-XXXX 0 = standby power supply card not fitted 1 = 12VDC standby power supply card fitted 2 = 24VDC standby power supply card fitted 4 = 48VDC standby power supply card fitted TBA3XXX-XXXX 0 = auxiliary power supply PCB not fitted 1 = 12VDC auxiliary power supply PCB fitted 2 = 24VDC auxiliary power supply PCB fitted 4 = 48VDC auxiliary power supply PCB fitted TBA3XXX-XXXX 0 = default TBA3XXX-XXXX 0 = default Power Management Unit Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 7.1 Identifying the PMU PCBs AC converter PCB top view standby power supply card PFC control card battery control card auxiliary power supply PCB DC converter PCB bottom view DC converter PCB HVDC control and microprocessor card DC control card AC converter PCB AC and DC PMU shown TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Servicing 117 Screw Torque Settings The recommended torque settings for the screws used in the PMU are as follows: Location / Function Torque Driver ■ securing the front and rear panels to 2.0N·m / 18lbf·in the heatsinks ■ securing the AC and DC converter PCBs to the heatsinks ■ securing the bus bars to the DC converter PCB ■ securing the top and bottom covers 0.5N·m / 4.5lbf·in to the front and rear panels ■ securing the handle to the front panel ■ securing the DC input filter card to the bus bars securing the 500W DC transformer primary wires into their terminals 1.8N·m / 16lbf·in Size T20 M4 T10 M3 flat blade Removing the Top and Bottom Covers 1. Note 2. Remove the four M3 Torx screws securing the top cover to the front and rear panels. Lift off the top cover. If the top cover is difficult to move, we suggest you lift one end of the cover away from the end panel with a flat-blade screwdriver. The cover should then be loose enough to lift off. Turn the PMU over and remove the four M3 Torx screws securing the bottom cover to the front and rear panels. Lift off the bottom cover. Removing the Front and Rear Panels 118 1. Remove the M4 Torx Taptite screw securing the front panel to the AC converter PCB. 2. Remove the five M4 Torx Taptite screws securing the front panel to the heatsinks and shield. Slide the front panel off the heatsinks. 3. Remove the M4 Torx Taptite screw securing the rear panel to the AC converter PCB. Power Management Unit Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 4. Remove the five M4 Torx Taptite screws securing the rear panel to the heatsinks and shield. 5. Loosen the rear panel slightly and remove the fibreglass DC input insulator from behind the DC input terminals. Slide the rear panel off the heatsinks. Disconnecting the AC and DC Modules Unless otherwise indicated, the circled numbers in the following instructions refer to Figure 7.2 on page 120. 1. As shown in Figure 7.3 on page 121, rotate the PMU so that the DC module f is on top of the AC module g and unplug the 12-way ribbon cable h from the DC converter PCB. 2. Unfold the DC module from on top of the AC module, and place it end-to-end with the AC module, as shown in Figure 7.2. 3. Unplug the 28VDC cable b from the DC converter PCB. 4. If fitted, unplug the 8-way cable c from the auxiliary power supply PCB. Remove the cable from the retaining clips d. Note 5. These connectors have locking tabs. You must disengage the locking tab before you can remove the plug from the socket. Slide the plastic grommet e out of the shield f . Unplug the mains input connector g from the AC converter PCB and remove the shield. Reconnecting the AC and DC Modules Unless otherwise indicated, the circled numbers in the following instructions refer to Figure 7.3 on page 121. 1. If previously removed, reconnect the 28VDC cable b, 12-way ribbon cable c, and 8-way cable d (if fitted) to the AC converter PCB and feed them through the plastic grommet e. 2. Reconnect the mains input connector to the AC converter PCB (as shown in Figure 7.2 on page 120), then insert the plastic grommet holding the cables into the hole in the shield. 3. As shown in Figure 7.2, place the AC and DC modules end-to-end and reconnect the 28VDC cable b and 8-way cable c (if fitted). Position the 12-way ribbon cable h between the two modules so that it will still be accessible when the AC module is folded on top of the DC module. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Servicing 119 Figure 7.2 AC module f e 4. Fold the AC module f on top of the DC module g, ensuring that the cables and shield i are correctly positioned. Make sure that none of the cables is pinched between the modules and/or shield. 5. Reconnect the 12-way ribbon cable h to the DC converter PCB. Disconnecting the AC and DC Modules DC module h b d d c g 120 Power Management Unit Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 7.3 Reconnecting the AC and DC Modules c e b d f i h g TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Servicing 121 Refitting the Front and Rear Panels 1. Hold the two modules firmly together and fit the front panel over the heatsinks. Ensure that the shield remains in place. You may find it easier to fit the front panel while the PMU is lying on its side. This way the shield is held in place between the heatsinks. 2. Refit and tighten the five M4 Torx Taptite screws to secure the front panel to the heatsinks and shield. Note Make sure that all connectors are correctly located in their respective holes in the panel before fully tightening the screws. 3. Refit and tighten the M4 Torx Taptite screw securing the front panel to the AC converter PCB. 4. Fit the rear panel over the heatsinks. 5. Slide the fibreglass DC input insulator in behind the DC input terminals. Make sure it fits into the slot in the PCB b and is correctly located on its mounting tabs in the rear panel c. 6. Refit and tighten the five M4 Torx Taptite screws to secure the rear panel to the heatsinks and shield. Note 7. Before fully tightening the screws, make sure that all connectors, switches and the fibreglass insulator are correctly located in their respective holes in the panel. c b Refit and tighten the M4 Torx Taptite screw securing the rear panel to the AC converter PCB. Refitting the Top and Bottom Covers 1. Note 2. 122 Refit the bottom cover over the front and rear panels and secure with the four M3 Torx screws. The bottom cover cannot be fitted to the top of the PMU as the mounting holes in the cover will not align with the holes in the front and rear panels. Turn the PMU over and align the top cover over the front and rear panels. Carefully slide the cover down until the locating tabs engage with the bottom cover. Ensure that the fibreglass DC input insulator sits inside the top cover. Power Management Unit Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 3. Push the top cover down firmly and secure with the four M3 Torx screws. Note 7.3 Both the top and bottom covers are symmetrical and can be fitted in either orientation. Replacing the Plug-in Cards Important You must reprogram the PMU if you fit a replacement HVDC and microprocessor card, or change the configuration of the PMU. Refer to “Reprogramming” on page 125. Important The HVDC and microprocessor card normally fitted to a DC PMU does not have the HVDC circuitry fitted. Do not fit this type of card to a PMU with an AC module or the AC module will be damaged. You can, however, safely fit a card with the HVDC circuitry to any model of PMU. Important The DC input voltage of a replacement standby power supply card must match the DC input voltage of the DC module (i.e 12VDC, 24VDC or 48VDC nominal). Fitting a card with the wrong input voltage may damage the DC module. Important We strongly recommend that you use the TB8100 card remover1, as shown in Figure 7.4 on page 124. A flat-blade screwdriver may reach too far through the slot and damage the components on the card. Refer to Section 7.2 “Disassembly and Reassembly” for details on removing and refitting the top and bottom covers and front panel. Removal - Method 1 This procedure applies to the standby power supply and PFC control cards. The procedure for removing the other cards is described in Method 2 below. 1. Remove the top cover. 2. Insert the card remover into the slot in the AC or DC converter PCB b and push down c to lift the nearest plug out of its socket (refer to Figure 7.4). 1. The card remover is included in the TBA0ST2 tool kit, which is available from your nearest Tait Dealer or Customer Service Organisation. It is also available separately as part number 220-02034-01. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Servicing 123 Figure 7.4 3. Repeat this procedure at the other end of the card. 4. When all plugs are free of their sockets, slide the card out from the groove in the heatsink. Replacing the Plug-in Cards c b e d g g f 124 Power Management Unit Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Removal - Method 2 Refitting Reprogramming This procedure applies to the DC control, battery control, and HVDC and microprocessor cards. 1. Remove the top and bottom covers and front panel. 2. Insert the card remover between the card and the edge of the AC or DC converter PCB d and push down e to lift the nearest plug out of its socket (refer to Figure 7.4). 3. Insert the card remover into the slot near the other end of the card and push down to lift the plug out of its socket. On the longer HVDC and microprocessor card, repeat this procedure for each slot along the length of the card, working from the front to the rear of the PMU. 4. When all plugs are free of their sockets, slide the card out from the groove in the heatsink. 1. Insert the top of the card into the groove in the heatsink f . 2. Align the plugs on the card with their matching sockets on the AC or DC converter PCB. 3. Press the card down firmly at each end g so that each plug fits correctly into its matching socket. There should be an audible “click” when each plug is fully inserted. On the longer HVDC and microprocessor card, you may need to use both hands to press evenly along its length. 4. Refit the front panel and covers as necessary. If you have replaced the HVDC and microprocessor card, you will have to reprogram the PMU as described in the table below. Procedure Details reprogram the product code reprogram this information into the PMU using the Calibration Kit software; refer to the Calibration Kit documentation for more details replace the serial number label the serial number of the PMU will change to the number already programmed into the replacement HVDC and microprocessor card; stick the new serial number label onto the rear panel If you have changed the configuration of the PMU by fitting or removing a standby power supply card, you will have to reprogram the PMU as described in the table below. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Servicing 125 Procedure Details reprogram the product code use the Calibration Kit software to reprogram the PMU with the product code which corresponds to the new configuration of the PMU; for more details refer to “Identifying the PMU” on page 116, and to the Calibration Kit documentation There is no need for any recalibration when any of the plug-in cards is fitted, removed or replaced. 7.4 Replacing the Auxiliary Power Supply PCB Important You must reprogram the PMU if you change its configuration by fitting or removing an auxiliary power supply PCB. Refer to “Reprogramming” on page 127. Refer to Section 7.2 “Disassembly and Reassembly” for details on removing and refitting the top and bottom covers and rear panel. The circled numbers in the following instructions refer to Figure 7.5. Figure 7.5 Replacing the Auxiliary Power Supply PCB c 126 Power Management Unit Servicing b TB8100 Service Manual © Tait Electronics Ltd April 2004 Removal Refitting Reprogramming 1. Remove the top and bottom covers and rear panel. 2. Unplug the loom b from the auxiliary power supply PCB. 3. Remove the two M4 Torx Taptite screws c securing the PCB to the heatsink. 1. Position the PCB as shown in Figure 7.5 and secure with the two M4 Torx Taptite screws c. 2. Reconnect the loom b. 3. Replace the rear panel and top and bottom covers. If you have changed the configuration of the PMU by fitting or removing an auxiliary power supply PCB, you will have to reprogram the PMU as described in the table below. Procedure reprogram the product code Details use the Calibration Kit software to reprogram the PMU with the product code which corresponds to the new configuration of the PMU; for more details refer to “Identifying the PMU” on page 116, and to the Calibration Kit documentation There is no need for any recalibration when this PCB is fitted, removed or replaced. TB8100 Service Manual © Tait Electronics Ltd April 2004 Power Management Unit Servicing 127 128 Power Management Unit Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 7.6 PMU Mechanical Assembly - Sheet 1 Description IPN Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. b c d e f g h i j 1) 1! 1@ 1# 1$ 1% 1^ 1& 1* 1( 2) 2! 2@ 2# 2$ 2% 2^ current transformer 053-00028-XX E-core choke 069-00010-40 clamp for E-core choke 069-00010-41 AC mains input connector 219-02843-XX E-core choke PCB 220-02023-XX 4mm bus bar terminal 240-04030-44 retaining clip (holds device against heatsink) 303-50040-XX handle 308-01065-XX heatsink 308-13146-XX heatsink insulator 309-01051-XX DC input insulator 309-01052-XX bottom cover 316-06811-XX front panel 316-06812-XX rear panel 316-06813-XX top cover 316-06814-XX shield 319-01246-XX M6x12mm pan head Pozidriv screw 345-00070-05 M3x6mm countersunk Torx screw 345-40460-XX M3x8mm pan head Torx Taptite screw 349-00020-36 M4x12mm pan head Torx Taptite screw 349-02058-XX M3x10mm pan head Torx Taptite screw 349-02066-XX 1) x1 per wire retaining clip (if 40W aux. PS PCB fitted) 357-01051-XX heatsink plastic grommet 360-02026-XX M3 T03 insulator bush 362-00010-11 10mm ID insulator bush with shoulder 362-00011-XX seal (when 40W aux. PS PCB not fitted) 362-01122-XX 2& 2* 2( 3) 3! 3@ 3# AC converter PCB PFC control card 1* x4 Note: This drawing shows an AC and DC PMU. Those parts fitted only to an AC PMU or a DC PMU are shown in sheet 2. 1% j c x2 3) 2) d x2 3# 1! 1& x2 h 1(2$ x3 1$ f x2 2% x2 per 3! transformer 2^ 2) b HVDC control and microprocessor card e x2 DC converter PCB g x3 DC input filter card DC control card 2# 1^ 3@ battery control card 12-way ribbon cable between AC and DC modules 219-02629-XX 8-way cable for auxiliary power supply PCB 219-02844-XX 28VDC cable between AC and DC modules 219-02846-XX 2! thermally conductive insulator sheet 16x22mm 362-01116-XX x2 thermally conductive insulator sheet 130x22mm 362-01117-XX 2& 2@ x3 1# Not Shown in this Drawing j 2* j i 2) x5 each end TB8100 Service Manual © Tait Electronics Ltd April 2004 j 1* x4 1@ 2( each 2) x7module Power Management Unit Servicing 129 Figure 7.7 PMU Mechanical Assembly - Sheet 2 Description IPN b DC PMU b c d AC converter PCB mounting bracket 302-05268-XX heatsink insulator 309-01051-XX M4x12mm pan head Torx Taptite screw 349-02058-XX e AC converter PCB (current sense and output filter circuitry only) f g PFC control card DC PMU This drawing shows the assembly of the AC module when it is fitted to a DC PMU. c f HVDC control and microprocessor card (feedback and microprocessor circuitry only) AC PMU h i j 1) 1! d x4 DC input insulator 309-01052-XX rear panel 316-06813-XX AC blanking plate 316-06836-XX M4x12mm pan head Torx Taptite screw 349-02058-XX seal (when 40W aux. PS PCB not fitted) 362-01122-XX b Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. e c g AC PMU This drawing shows the blanking plates fitted to the front and rear panels in an AC PMU. These plates cover the holes normally covered by the DC module heatsinks. h 1) x4 each end j x2 each end i 1! 130 Power Management Unit Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 8 Control Panel Circuit Description The control panel is designed to be the link between the user and the TB8100 BSS. The circuitry for the operation of the control panel is located on a PCB mounted behind its front face. All communication between the BSS and the control panel is via the system control bus. Figure 8.1 on page 132 shows the configuration of the main circuit blocks, and the main inputs and outputs for power, audio and control signals. This chapter provides an overview of all the control panel circuitry1. However, not all the circuitry described here will be fitted to any particular control panel PCB. The different types of PCB and their main features are listed in the following table. Control Panel PCB Feature Standard programming port ■ microphone socket ■ volume control knob ■ 0.5W speaker ■ PTT key from microphone ■ LED indicators ■ channel speaker button ■ channel carrier button ■ microphone channel select button ■ Power Save ■ ■ 1. For a description of the controls located on the control panel, refer to “Operating Controls” in the Installation and Operation Manual. TB8100 Service Manual © Tait Electronics Ltd April 2004 Control Panel Circuit Description 131 Figure 8.1 Control Panel High Level Block Diagrams Standard Control Panel Microphone Audio Microphone Pre-emphasis & Gain Control Microphone Connector Speaker Audio Speaker Enable 2 I C Bus System Control Bus Speaker Volume & Gain Control Speaker Control Panel Type 2 IC Translation LEDs & Switches 28V, GND Power Supply Fan Inputs Fan Power & GND Open Collector RS-232 RS-232 Translation RS-232 Bus RS-232 Connector RS-232 Translation RS-232 Bus RS-232 Connector Power Save Control Panel Open Collector RS-232 Full Power On System Control Bus 28V, GND Power Supply Control Panel Type Power Save On LEDs 2 I C Bus IC Translation Fan Power & GND 132 2 Control Panel Circuit Description Fan Inputs TB8100 Service Manual © Tait Electronics Ltd April 2004 8.1 Control Circuitry The control panel translates I2C messages into an appropriate response on the LEDs. It also translates key inputs from the front panel membrane1 and fan rotation inputs from both fans into appropriate I2C messages. The type of control panel is also sent with I2C messages. The control panel translates RS-232 from the programming port into 0V to 5V open-collector signals which feed from and drive up to seven reciters. 8.2 Audio Circuitry This circuitry is present only on the standard control panel PCB. The audio input level from the reciter is 1V pp for a single reciter. When multiple reciters are connected, this input level will drop by approximately 1⁄ (number of reciters), to a minimum of 167mV pp for seven reciters. The volume of the speaker is controlled by the volume control knob. In addition, the control panel performs gain control so that, with an input of 167mV pp, the power output into a 16Ω speaker is ≥0.5W at the maximum position of the knob, and 0W at the minimum position of the knob. An LED indicates when the speaker is on. The control panel is designed to work with an electret microphone with an input range of 80dBSPL to 115dBSPL. 8.3 Power Save This circuitry is present only on the power save control panel PCB. When the BSS enters power save mode, the control panel will shut down after receiving the appropriate I2C bus message from the reciter. The power LED flashes once every two seconds to indicate the BSS is in power save mode. The control panel will power up again when it receives a signal on the RS-232 system control bus or serial port. 1. Standard control panel only. TB8100 Service Manual © Tait Electronics Ltd April 2004 Control Panel Circuit Description 133 8.4 Power Supply The control panel operates off a 28V (nominal) power supply provided by the reciter. The power supply for the cooling fans mounted on the front panel is fed through the control panel. 134 Control Panel Circuit Description TB8100 Service Manual © Tait Electronics Ltd April 2004 9 Control Panel Servicing Important This equipment contains devices which are susceptible to damage from static charges. Refer to “ESD Precautions” on page 15 for more information on antistatic procedures when handling these devices. This chapter provides information on how to identify, remove and replace the main mechanical parts and PCB. Figure 9.4 on page 141 identifies the main mechanical parts, and “Identifying the Control Panel” on page 136 explains how to identify the model of control panel from its product code. Note TB8100 Service Manual © Tait Electronics Ltd April 2004 For the sake of simplicity and clarity, the instructions and illustrations in this chapter refer to a standard control panel. However, the same basic procedures and techniques apply to other models. Control Panel Servicing 135 9.1 Identifying the Control Panel You can identify the model of control panel by referring to the product code printed on a label on the side of the chassis. The product codes are explained in the table below. Product Code 9.2 Description TBA201X power save TBA202X standard Screw Torque Settings The recommended torque settings for the screws and nuts used in the control panel are as follows: Location / Function ■ securing the PCB ■ securing the D-range connector securing the speaker clamps 9.3 Driver/ Spanner Torque Size 0.5N·m / 4.5lbf·in T10 M3 0.5N·m / 4.5lbf·in 5.5mm AF M3 Replacing the PCB The circled numbers in the following instructions refer to Figure 9.1. Removal 136 1. Gently pull the volume knob off its shaft. 2. Disconnect the speaker plug b from the socket on the PCB. 3. Remove the M3 Torx screws c securing the PCB and D-range connector. 4. Carefully lift and rotate the PCB away from the control panel chassis, feeding the shaft of the volume control through the hole in the chassis, until the PCB is standing upright d. 5. With the PCB standing upright, disconnect the flexible connector to the keypad e. Control Panel Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 9.1 Replacing the Control Panel PCB b c x4 d c x2 e e TB8100 Service Manual © Tait Electronics Ltd April 2004 Control Panel Servicing 137 Refitting 1. Withdraw the flexible connector to the keypad through the hole in the side of the control panel chassis. 2. Refit the PCB to the chassis, feeding the speaker wire through the hole in the PCB. Secure the PCB and D-range connector with the M3 Torx screws. 3. Reconnect the speaker wire. 4. Insert the flexible connector into its socket on the PCB through the hole in the side of the chassis. Important 5. Make sure the flexible connector is correctly positioned and latched in its socket, as shown in Figure 9.2. Refit the volume knob. Figure 9.2 Reconnecting the Flexible Connector latch pushed fully down at both ends flexible connector inserted straight into socket 138 Control Panel Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 9.4 Replacing the Speaker The circled numbers in the following instructions refer to Figure 9.3. Removal Refitting 1. Remove the PCB as described in “Replacing the PCB” on page 136. 2. Remove the M3 nuts and spring washers b and then remove the brackets c. 3. Remove the speaker. 1. To refit the speaker, follow the removal instructions in reverse order. Tighten the M3 nuts to the correct torque. Important 2. Make sure the speaker is correctly aligned as shown in Figure 9.3 so that the wire will fit through the slot in the PCB (refer to Figure 9.1 on page 137). Refit the PCB as described in “Replacing the PCB” on page 136. Figure 9.3 Replacing the Speaker b x2 c x2 TB8100 Service Manual © Tait Electronics Ltd April 2004 Control Panel Servicing 139 140 Control Panel Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 9.4 Control Panel Mechanical Assembly Description IPN b c d e f g D-range to Micromatch ribbon cable 219-02853-XX speaker* 252-00011-XX speaker mounting bracket* 302-05266-XX speaker grille cloth* 307-01024-XX volume knob* 311-01054-XX keypad - standard keypad - power save 311-03116-XX 311-03115-XX h i chassis 316-06820-XX M3x8mm pan head Torx screw with spring & flat washers 345-40470-XX j 1) M3 hex nut* 352-00010-08 M3 spring washer* 353-00010-12 1! control panel PCB Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. f h d x2 1) x2 1! j x2 Note: This drawing shows a standard control panel. Any differences between the standard and power save control panels are indicated in the description of the parts, or as shown below: * fitted to standard control panel only g e b i x2 c i x4 TB8100 Service Manual © Tait Electronics Ltd April 2004 Control Panel Servicing 141 142 Control Panel Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 10 Subrack Servicing This chapter provides information on the standard mechanical parts and cables used in the TB8100 BSS: ■ Figure 10.1 on page 145 identifies the mechanical parts used in the front panel assembly ■ Figure 10.2 on page 146 identifies the mechanical parts used in the subrack assembly ■ Figure 10.3 on page 147 identifies the cables used in single and dual base station systems. TB8100 Service Manual © Tait Electronics Ltd April 2004 Subrack Servicing 143 144 Subrack Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 10.1 Front Panel Mechanical Assembly Description b c d e f g h i j 1) IPN fan contact PCB 220-02028-XX fan: no rotation sensor rotation sensor 258-00011-XX 258-00014-XX PA fan duct 302-05264-XX PMU fan duct 302-05265-XX spring clip 303-50106-XX front panel 316-06821-XX KC30x10mm pan head Torx PT screw 346-10030-10 M4x40mm pan flange head Torx PT screw 346-10440-XX quarter-turn fastener 354-01047-XX retaining washer for quarter-turn fastener 354-01048-XX g i x8 c j x2 e Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. Note: Fully-assembled front panels and replacement fan kits are also available as separate products. Consult your nearest Tait Dealer or Customer Service Organisation for details on the availability of these products. 1) x2 b f TB8100 Service Manual © Tait Electronics Ltd April 2004 h c h x6 d Subrack Servicing 145 Figure 10.2 Subrack Mechanical Assembly Description b c d e f g h i j 1) 1! 1@ 1# 1$ 1% IPN module retaining clamp 303-50102-XX cable retaining clip 303-50104-XX bottom guide rail 307-02052-XX top guide rail (also used in the bottom corners when required) 307-02053-XX rear blanking panel 316-06785-XX subrack 318-01051-XX M4x10mm pan head Pozidriv screw 345-00050-07 M3 hex nut 352-00010-08 M3 spring washer 353-00010-12 receptacle for quarter-turn fastener 354-01049-XX subrack ground connector 356-00010-61 9.5mm P-clip 357-00010-48 insulating foam 362-01037-XX insulator for interconnect PCB 362-01121-XX g 1! c x5 f e interconnect PCB Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. Note: Some of the parts illustrated in this diagram are also available as part of a kit or set of parts. These kits or sets are available as separate products. Consult your nearest Tait Dealer or Customer Service Organisation for details on the availability of these products. 1@ i x3 d j x3 1% 1) x2 1$ 1# h 146 b Subrack Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Figure 10.3 Cable Identification Description IPN b c d e RF coaxial cable - reciter to 5/50W PA (long) 219-02859-XX RF coaxial cable - reciter to 5/50W PA (short) 219-02862-XX RF coaxial cable - reciter to 100W PA 219-02864-XX f system control bus ribbon cable - 5/50W PA to subrack interconnect PCB 219-02861-XX g system control bus ribbon cable - PMU and 5/50W PA to subrack interconnect PCB 219-02857-XX h system control bus ribbon cable - PMU and 100W PA to subrack interconnect PCB 219-02863-XX i j 1) DC power cable - PMU to single reciter 219-02856-XX DC power cable - PMU to dual reciters 219-02860-XX system control bus ribbon cable - reciter to subrack 219-02858-XX interconnect PCB j c b e g f dual 5/50W BSS - front view DC power cable - PMU aux. output to single reciter 219-02895-XX DC power cable - PMU aux. output to dual reciters 219-02896-XX Note: The characters XX in an IPN (Tait Internal Part Number) stand for the issue number of the part. Only the latest issue of each part will normally be available for ordering as spare or replacement parts. Note: The cables illustrated in this diagram are also available as part of a wiring kit. These kits are available as separate products. Consult your nearest Tait Dealer or Customer Service Organisation for details on the availability of these products. i h e d single 100W BSS - front view 1) dual 5/50W BSS - rear view TB8100 Service Manual © Tait Electronics Ltd April 2004 Subrack Servicing 147 148 Subrack Servicing TB8100 Service Manual © Tait Electronics Ltd April 2004 Glossary This glossary contains an alphabetical list of terms and abbreviations related to the TB8100 base station system. For information about trunking, mobile, or portable terms, consult the glossary provided with the relevant documentation. ABCDEFGHIKLNPRSTUVW A access level There are three different levels of access to a base station: Administrator, User, and Read-only. The User access level has a configurable access profile; the Administrator decides which functions that access level can carry out. action An action is the second part of a Task Manager task. It specifies what the base station must do when the first part (the input) becomes true. active Digital outputs are active when the base station pulls their voltage low and current is flowing. Digital inputs are active when external equipment is pulling them to ground. All base station digital inputs and outputs are open collector. ADC Analog-to-Digital Converter. A device for converting an analog signal to a digital signal that represents the same information. Alarm log The alarm log is a list of the last 50 alarms that the base station generated. This list is stored in the base station. To view it, select Monitor > Alarms > Reported Alarms. Alarm Center Alarm Center is a utility provided with the Service Kit that is able to receive, store, and display alarms from any number of base stations with dial-up connections. Participating base stations need an Alarm Reporting license. Alarm Center also routes emailed messages to the email server. alarm notification Alarm notification is the process by which the base station passes on information about an alarm condition. It can notify alarms over the air, over the line, via email, or to an Alarm Center. It can also activate a digital output. If the Service Kit is logged on to the base station, it is automatically notified of any alarms. air intake temperature The temperature of the air as measured at the PA’s air intake. TB8100 Service Manual © Tait Electronics Ltd April 2004 Glossary 149 anti-kerchunking Anti-kerchunking is a base station configuration that discourages users from kerchunking. B balanced line A balanced line has two wires carrying equal and opposite signals. It is typically used in a line-connected base station for connecting to the despatcher console. The system interface identifies the balanced line in as Rx+ and Rx-, and the balanced line out as Tx+ and Tx-. BCD BCD (binary coded decimal) is a code in which a string of four binary digits represents a decimal number. BSS A BSS (base station system) is a subrack containing at least one TB8100 base station. C Calibration Kit The TB8100 Calibration Kit is a utility for defining the switching ranges of the receiver and the exciter and for flattening the receiver response across its switching range. It can also be used to calibrate various parts of the reciter and the PA circuitry. CCDI2 CCDI2 (computer controlled data interface version 2) is a proprietary Tait command protocol used between computer equipment and a Tait radio. channel A channel is: ■ A frequency pair (or just a single frequency in a simplex system). ■ A set of configuration information that defines the frequency pair and other settings. Also referred to as a channel configuration. Generally, ‘channel’ has this meaning in the Service Kit. channel profile A channel profile is a named set of configuration items relating to the base station’s RF configuration, transmitter power output and power saving modes. Like the signalling profile, it can be applied to any channel. Together, these profiles define most configuration items. channel spacing Channel spacing is the bandwidth that a channel nominally occupies. If a base station has a channel spacing of 12.5 kHz, there must be a separation of at least 12.5 kHz between its operating frequencies and those of any other equipment. channel table The channel table is the base station’s database of channel configurations. To view it, select Configure > Base Station > Channel Table. 150 Glossary TB8100 Service Manual © Tait Electronics Ltd April 2004 CODEC An IC which combines analog-to-digital conversion (coding) and digitalto-analog conversion (decoding). configuration file A configuration file consists of all the configuration settings needed for a base station, stored as a file in the configurations folder. Configuration files have the extension *.t8c. connection A connection is a named group of settings that the Service Kit uses when establishing communications with a BSS. control bus The control bus is used for communications between modules in a base station system. It is an I2C bus, a bi-directional two-wire serial bus which is used to connect integrated circuits (ICs). I2C is a multi-master bus, which means that multiple chips can be connected to the same bus, and each one can act as a master by initiating a data transfer. control panel The control panel is an area at the front of the BSS with buttons, LEDs and other controls that let you interact with the BSS. CTCSS CTCSS (continuous tone controlled squelch system), also known as PL (private line), is a type of signalling that uses subaudible tones to segregate groups of users. custom action A custom action is a user-defined Task Manager action that consists of more than one pre-defined action. custom input A custom input is a user-defined Task Manager input that consists of a combination of pre-defined inputs. CWID CWID (Continuous Wave IDentification) is a method of automatically identifying the base station using a Morse code. Continuous wave means transmission of a signal with a single frequency that is either on or off, as opposed to a modulated carrier. D DAC Digital-to-Analog Converter. A device for converting a digital signal to an analog signal that represents the same information. DCS DCS (digital coded squelch), also known as DPL (digital private line), is a type of subaudible signalling used for segregating groups of users. DCS codes are identified by a three-digit octal number, which forms part of the continuously repeating code word. When assigning DCS signalling for a channel, you specify the three-digit code. de-emphasis De-emphasis is a process in the receiver that restores pre-emphasised audio to its original relative proportions. TB8100 Service Manual © Tait Electronics Ltd April 2004 Glossary 151 duty cycle Duty cycle is used in relation to the PA. It is the proportion of time (expressed as a percentage) during which the PA is operated. The TB8100 PA can be operated continuously. E EIA Electronic Industries Alliance. Accredited by the American National Standards Institute (ANSI) and responsible for developing telecommunications and electronics standards in the USA. EMC Electromagnetic Compatibility. The ability of equipment to operate in its electromagnetic environment without creating interference with other devices. ETSI European Telecommunications Standards Institute. The non-profit organisation responsible for producing European telecommunications standards. F flag A flag is a programming term for a “yes/no” indicator used to represent the current status of something. The base station has a set of system flags that are read and set by Task Manager. There is also a separate set of flags that you can use in your own Task Manager tasks. frequency band The range of frequencies that the equipment is capable of operating on. front panel The cover over the front of the BSS containing fans for the PA and PMU. G Gating is the process of opening and closing the receiver gate. When a valid signal is received, the receiver gate opens. gating H hiccup mode Many power supplies switch off in the event of a short-circuit and try to start again after a short time (usually after a few seconds). This “hiccup”-type of switching off and on is repeated until the problem is eliminated. hysteresis Hysteresis is the difference between the upper and lower trigger points. For example, the receiver gate opens when the upper trigger point is reached, 152 Glossary TB8100 Service Manual © Tait Electronics Ltd April 2004 but will not close until the level falls to the lower trigger point. An adequate hysteresis prevents the receiver gate from repeatedly opening and closing when the level is about that of the trigger point. Hysteresis mode A mode of PMU operation designed to save power. The PMU is mainly turned off, but switches back on intermittently to maintain output voltage when the output current is low. I inactive Digital outputs are inactive if the base station is doing nothing to them. They are floating, open collector outputs. Digital inputs are inactive when they are open circuit. Intercom mode Intercom mode makes it possible for the operator at the dispatch centre and the servicing technician at the base station to communicate with each other over the line. It connects the base station microphone to line out. isolator An isolator is a passive two-port device which transmits power in one direction, and absorbs power in the other direction. It is used in a PA to prevent damage to the RF circuitry from high reverse power. K kerchunking Kerchunking is transmitting for a second or less without saying anything in order to test the base station. This results in a ‘kerchunk’ sound. L line-controlled base station A TB8100 is a line-controlled base station when it receives audio (sending it out via its systems interface), transmits audio received over its systems interface, and its transmitter is keyed via the Tx Key line. logging on Once you are connected to a BSS, you log on to a base station. This establishes communications between the Service Kit and a particular base station. N navigation pane The navigation pane is the left-hand pane of the Service Kit application window. It displays a hierarchical list of items. When you click an item, the main pane displays the corresponding form. TB8100 Service Manual © Tait Electronics Ltd April 2004 Glossary 153 0 operating range Operating range is another term for switching range. P PA The PA (power amplifier) is a base station module that boosts the exciter output to transmit level. PMU The PMU (power management unit) is a module that provides power to the BSS. pre-emphasis Pre-emphasis is a process in the transmitter that boosts higher audio frequencies. R reciter The reciter is a module of a TB8100 base station that acts as receiver and exciter. reverse tone burst Reverse tone bursts can be used with CTCSS. When reverse tone bursts are enabled, the phase of the generated tones is reversed for a number of cycles just before transmission ceases. If the receiver is configured for reverse tone burst, it responds by closing its gate. RSSI RSSI (Received Signal Strength Indicator) is a level in dBm or volts that indicates the strength of the received signal. Run mode Run mode is the normal operating mode of the base station. signalling profile A signalling profile is a named set of configuration items related to signalling that can be applied to any channel. Items include subaudible signalling and transmit timers. S sensitivity The sensitivity of a radio receiver is the minimum input signal strength required to provide a useable signal. SINAD SINAD (Signal plus Noise and Distortion) is a measure of signal quality. It is the ratio of (signal + noise + distortion) to (noise + distortion). A SINAD of 12dB corresponds to a signal to noise ratio of 4:1. The TB8100 can provide an approximate SINAD value while in service by comparing the in- 154 Glossary TB8100 Service Manual © Tait Electronics Ltd April 2004 band audio against out-of-band noise. This value should not be relied upon to make calibrated measurements. Sleep mode Sleep mode is a power saving state in which a part of the base station is switched off, and then periodically switched on again. Standby mode Standby mode is a mode of base station operation in which active service is suspended so that special operations can be carried out, such as programming the base station with a new configuration. status message A status message is a set of information about the base station that can be emailed. It identifies the base station, indicates the current operating channel, lists the status of all alarms, and gives the current values of a number of other monitored parameters. It also contains the alarm log. subaudible signalling Subaudible signalling is signalling that is at the bottom end of the range of audible frequencies. The TB8100 base station supports CTCSS and DCS subaudible signalling. subtone A subtone (subaudible signalling tone) is a CTCSS tone or a DCS code. switching range The switching range is the range of frequencies (about 10MHz) that the equipment is tuned to operate on. This is a subset of the equipment’s frequency band. system flag System flags are binary indicators that are read and set by Task Manager. Generally, they are used to disable or enable configured base station functions. system interface The system interface is the set of inputs to and outputs from the base station (excluding power and RF), provided by a board inside the reciter. A range of different boards are available for different applications. T TB8100 Base Station A Tait TB8100 base station consists of the equipment necessary to receive and transmit on one channel. Generally, this means a reciter, a PA, and a PMU. Often abbreviated to TB8100 or base station. Talk Through Repeater A TB8100 is a talk through repeater when its audio path is configured to pass the audio it receives on to the transmitter. Task Manager Task Manager is a part of the TB8100 base station firmware that carries out tasks in response to inputs. These tasks are formulated using the Service Kit. TB8100 Service Manual © Tait Electronics Ltd April 2004 Glossary 155 template file A template file contains configuration information that can be used to create a new base station configuration. Template files have the extension *.t8t. transmit lockout The transmit lockout feature prevents the base station from transmitting for a time once the transmit timer has expired. It is designed to prevent users from monopolising the base station. U Unbalanced line An unbalanced line has one wire earthed. It is typically used for short connections, for example, between a base station and a repeater on the same site. The system interface identifies the wires of unbalanced lines with Rx audio, Tx audio, and Audio Ground. Audio Ground is common to line-in and line-out. V valid signal A valid signal is a signal that the receiver responds to by opening the receiver gate. A signal is valid for example when it is stronger than a minimum level and when it has the specified subtone. VSWR Voltage Standing Wave Ratio (VSWR) is the ratio of the maximum peak voltage anywhere on the line to the minimum value anywhere on the line. A perfectly matched line has a VSWR of 1:1. A high ratio indicates that the antenna subsystem is poorly matched. W Watchdog 156 Glossary A watchdog circuit checks that the system is still responding. If the system does not respond (because the firmware has locked up), the circuit resets the system. TB8100 Service Manual © Tait Electronics Ltd April 2004
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