TB8100 Service Manual TB8000/TB8100_Service_Manual/TB8100_Service_Manual

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Service Manual
Tait Contact Information
Contents
Preface
1 Safety and Servicing Information
2 Reciter Circuit Description
3 Reciter Servicing
4 Power Amplifier Circuit Description
- 4.1 Microprocessor Control Circuitry
- 4.2 RF Circuitry
5 Power Amplifier Servicing
6 Power Management Unit Circuit Description
7 Power Management Unit Servicing
8 Control Panel Circuit Description
9 Control Panel Servicing
10 Subrack Servicing
Glossary

MB8100-00-00-812

Issue 1

April 2004

TB8100 base station

Service Manual

2TB8100 Service Manual

Tait Contact Information

Tait Radio Communications http://www.taitworld.com

Corporate Head Office

New Zealand

Tait Electronics Ltd

P.O. Box 1645

Christchurch

New Zealand

E-mail: info@taitworld.com

We b s ite: http://www.taitworld.com

Technical Support:

E-mail: support@taitworld.com

We b s i t e : http://support.taitworld.com

Tait North America

Regional Head Office - United States of

America

Tait North America Inc.

E-mail: usa@taitworld.com

Canada

Tait North America Inc.

E-mail: canada@taitworld.com

Latin America

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

Tait North Asia

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

Oceania

New Zealand

Tait Communications Ltd

E-mail: headoffice@tcl.tait.co.nz

Australia

Tait Electronics (Aust) Pty Ltd

E-mail: australia@taitworld.com

Note: For the addresses and phone numbers

of the above regional offices refer to the

TaitWorld website.

TB8100 Service Manual 3

Contents

Tait Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Scope of Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Enquiries and Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Updates of Manual and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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

4TB8100 Service Manual

Reference Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.3 Receiver RF Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Front End . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Mixer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

IF Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

VCO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

AGC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2.4 Exciter RF Circuitry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Frequency Control Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

VCO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Exciter Control Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

2.5 System Interface PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

2.6 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3 Reciter Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

3.1 Disassembly and Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Identifying the Reciter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Screw Torque Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Removing the Covers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Removing the Front and Rear Panels . . . . . . . . . . . . . . . . . . . . . . . . . 54

Refitting the Front and Rear Panels . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Refitting the Covers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

3.2 Replacing the Digital PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

3.3 Replacing the System Interface PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

3.4 Replacing the RF PCB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4 Power Amplifier Circuit Description . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.1 Microprocessor Control Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Diagnostics and Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

PA-Key. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Foldback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Power Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Fan Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Temperature Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Ambient Air Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

4.2 RF Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

6W PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

60W PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Low Pass Filter and Directional Coupler PCB . . . . . . . . . . . . . . . . . . . 74

Splitter and Combiner PCBs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Interconnect PCBs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

TB8100 Service Manual 5

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

6TB8100 Service Manual

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

TB8100 Service Manual 7

List of Illustrations

Figure 1.1 Typical Antistatic Bench Set-up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 1.2 Identifying Torx Screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 1.3 Identifying Pozidriv and Philips Screws and Screwdrivers . . . . . . . . . . . . 17

Figure 2.1 Reciter High Level Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 2.2 Reciter Digital Circuitry Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 2.3 Reciter RISC Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 2.4 Reciter External Reference Block Diagram . . . . . . . . . . . . . . . . . . . . . . 29

Figure 2.5 Reciter Receiver RF Circuitry Block Diagram. . . . . . . . . . . . . . . . . . . . 31

Figure 2.6 Reciter Receiver Synthesizer Block Diagram . . . . . . . . . . . . . . . . . . . . . 32

Figure 2.7 Comparison of VCXO and VCO Modulation Responses . . . . . . . . . . . . 36

Figure 2.8 Reciter Exciter Synthesizer Modulator Block Diagram . . . . . . . . . . . . . . 37

Figure 2.9 Reciter System Interface PCB Block Diagram . . . . . . . . . . . . . . . . . . . . 41

Figure 2.10 Reciter Power Supply Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Figure 2.11 Identifying the Circuitry on the Digital and System Interface PCBs . . . . . 47

Figure 2.12 Identifying the Circuitry on the RF PCB . . . . . . . . . . . . . . . . . . . . . . . . 49

Figure 3.1 Identifying the Reciter PCBs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Figure 3.2 Removing the Front and Rear Panels. . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Figure 3.3 Replacing the Digital and System Interface PCBs . . . . . . . . . . . . . . . . . . 57

Figure 3.4 Reconnecting the Flexible Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . 58

Figure 3.5 Replacing the RF PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Figure 3.6 Reciter Mechanical Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Figure 4.1 PA High Level Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Figure 4.2 PA Control, RF and Power Supply Circuitry Block Diagram . . . . . . . . . 70

Figure 4.3 Identifying the Circuitry on the PA PCBs . . . . . . . . . . . . . . . . . . . . . . . 75

Figure 5.1 Identifying the PA PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Figure 5.2 Removing the Airflow Duct, Cover and Front Panel . . . . . . . . . . . . . . . 81

Figure 5.3 PCB Connecting Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Figure 5.4 Replacing the 6W PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Figure 5.5 Replacing the 60W PCB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Figure 5.6 Replacing the 60W RF Power Transistor . . . . . . . . . . . . . . . . . . . . . . . 88

Figure 5.7 Replacing the Control PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Figure 5.8 Replacing the LPF/Directional Coupler PCB. . . . . . . . . . . . . . . . . . . . . 92

Figure 5.9 Replacing the Splitter/Combiner PCBs . . . . . . . . . . . . . . . . . . . . . . . . . 94

Figure 5.10 PA Mechanical Assembly - Sheet 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Figure 5.11 PA Mechanical Assembly - Sheet 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Figure 6.1 PMU High Level Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Figure 6.2 PMU Microprocessor Functional Block Diagram . . . . . . . . . . . . . . . . . 102

Figure 6.3 PMU AC Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Figure 6.4 PMU DC Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Figure 6.5 Identifying the Circuitry on the AC Module PCBs. . . . . . . . . . . . . . . . 109

Figure 6.6 Identifying the Circuitry on the DC Module PCBs. . . . . . . . . . . . . . . . 111

Figure 7.1 Identifying the PMU PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Figure 7.2 Disconnecting the AC and DC Modules . . . . . . . . . . . . . . . . . . . . . . . 120

Figure 7.3 Reconnecting the AC and DC Modules. . . . . . . . . . . . . . . . . . . . . . . . 121

Figure 7.4 Replacing the Plug-in Cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Figure 7.5 Replacing the Auxiliary Power Supply PCB. . . . . . . . . . . . . . . . . . . . . 126

Figure 7.6 PMU Mechanical Assembly - Sheet 1 . . . . . . . . . . . . . . . . . . . . . . . . . 129

8TB8100 Service Manual

Figure 7.7 PMU Mechanical Assembly - Sheet 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 130

Figure 8.1 Control Panel High Level Block Diagrams. . . . . . . . . . . . . . . . . . . . . . . 132

Figure 9.1 Replacing the Control Panel PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

Figure 9.2 Reconnecting the Flexible Connector . . . . . . . . . . . . . . . . . . . . . . . . . . 138

Figure 9.3 Replacing the Speaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Figure 9.4 Control Panel Mechanical Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

Figure 10.1 Front Panel Mechanical Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

Figure 10.2 Subrack Mechanical Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

Figure 10.3 Cable Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

TB8100 Service Manual 9

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.

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.

10 TB8100 Service Manual

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 dam-

age 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 Organisa-

tion for more information.

TB8100 Service Manual 11

Publication Record

Issue Publication Date Description

1 April 2004 first release

12 TB8100 Service Manual

TB8100 Service Manual Safety and Servicing Information 13

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!! Do not operate TB8100 BSS equipment near

electrical blasting caps or in an explosive atmos-

phere. Operating the equipment in these envi-

ronments is a definite safety hazard.

14 Safety and Servicing Information TB8100 Service Manual

Beryllium Oxide

Caution The termination resistors used in the 100W power

amplifier contain some beryllium oxide. This sub-

stance 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 termina-

tion 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 accord-

ing 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).

Caution The magnetics and power devices attached to the

heatsink in the PMU get hot when they are operat-

ing. 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.

TB8100 Service Manual Safety and Servicing Information 15

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.

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.

Figure 1.1 Typical Antistatic Bench Set-up

common point ground

(building ground or

mains ground via 1M

ohm series resistor)

conductive wrist strap dissipative rubber

bench mat

16 Safety and Servicing Information TB8100 Service Manual

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).

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.

Figure 1.2 Identifying Torx Screws

“star” shaped recess with

six internal notches

TB8100 Service Manual Safety and Servicing Information 17

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

internal notches

Pozidriv Philips

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

18 Safety and Servicing Information TB8100 Service Manual

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.

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 Surface mount devices (SMDs) require special storage, han-

dling, removal and replacement techniques. This equip-

ment should be serviced only by an approved Tait Dealer or

Customer Service Organisation equipped with the neces-

sary 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.

Driver/

Spanner Size Location / Function

Tor x T 8 a

a. Included in the TBA0ST2 tool kit.

M2.5 securing the SMA connector to the reciter and PA

front panel

Tor x T 1 0 aM3 all M3 screws

Tor x T 2 0 aM4 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 AFaM3 securing the speaker to the control panel chassis

11mm AF securing the BNC/TNC connectors to the reciter rear

panel

TB8100 Service Manual Safety and Servicing Information 19

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 plated-

through 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 The desoldering iron does not usually have enough heat to desol-

der 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).

Component Cutting

Method 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.

20 Safety and Servicing Information TB8100 Service Manual

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).

TB8100 Service Manual Reciter Circuit Description 21

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

DSP

CODEC

40MHz

Clock

Receiver

Exciter

Synthesizer

Subsystem

Reference

Frequency

Subsystem

Digital

Receiver

Power

Supply

Power

Supply

RISC

DSP/RISC

CODECs

12.8MHz

Ref.

RF I/P

28VDC I/P

28V

28V 5V

3.3V

9.3V

RF O/P +

PA Key Audio

System

Control Bus System I/O

Digital

Receiver

Audio &

RSSI

Control &

Communications

Control &

Communications

Modulation

& Frequency

Control

Control &

Communications

External

Reference

Frequency

(if used)

RF PCB Digital PCB

System

Interface

PCB

22 Reciter Circuit Description TB8100 Service Manual

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 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, pre-

emphasis and low pass filtering

■signal path switching

■signal level adjustment

TB8100 Service Manual Reciter Circuit Description 23

■peak FM deviation limiting

■FM signal generation by controlling the dual point modulator

■calibration parameter estimation

■line level monitoring.

Receive Functions The DSP performs the following receive functions:

■detection of CTCSS and DCS signalling

■audio filtering: including removal of sub-audible components, de-

emphasis 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.

24 Reciter Circuit Description TB8100 Service Manual

Figure 2.2 Reciter Digital Circuitry Block Diagram

RSSI

Process

Loopback

Crosspoint

Switch

Demodulation

Rx Audio

Processor

DDCADC

Crosspoint

Switch

Interface

(serial

port)

CODECs

& Signal

Conditioning

Interface

(RISC/

DSP)

Crosspoint

Switch

DSP

Frequency

Control Loop

Section

Tx Audio

Processor

Signalling

Processor

Audio & DC

Measurement

Noise

Mute

serial port

Interface

(RISC/

DSP)

RISC

serial port

CODECs

& Signal

Conditioning

serial port

CODECs

& Signal

Conditioning

serial port

Tx VCO

Synthesiser

Tx VCXO

Frequency

Control Loop

Section

RF PCBDigital PCB

Control Panel PCB

Digital Signal

Paths

DSPDigital IF

System Interface PCB

Speaker

Microphone

Programming Port

LEDs and Switches

RSSI

Balanced Audio Output

Unbalanced Audio Output

Balanced Audio Input

Discrete I/O & SIO Bus

Unbalanced Audio Input

VCO Modulation

VCXO Modulation

VCO Control Feedback

FCL I

FCL Q

40MHz Clock

70.1MHz IF

from RF PCB 40MSPS

TB8100 Service Manual Reciter Circuit Description 25

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

■I2C for communication with the control panel and other modules in the

subrack.

Responsibilities 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.

26 Reciter Circuit Description TB8100 Service Manual

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.

TB8100 Service Manual Reciter Circuit Description 27

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_N-

based 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.

Figure 2.3 Reciter RISC Functional Block Diagram

Reciter

Status

External

Reference

Detect/

Select

RISC

40MHz

Clock

Synthesizers

Flash

RAM

DSP

System

Control

Bus

System

Interface

PCB

Interrupt

Main Loop

Debug LEDs

DIP Switch

SPI SPI

Chip Selects Chip Selects

Lock Detects

Detect 10MHz or

12.8MHz External

System I/O

System Control Bus

to BSS Modules &

Control Panel

10MHz or

12.8MHz

Internal TCXO

Rx L.O.

Ex L.O.

12.8MHz

40MHz

Select

Address, Data, Control

Flash Programming Voltages

Alarm LEDs

UART

Fan Good

SPI

Select

Rx Gate

Tx Relay

Tx Key

Hex Switch

Test

Digital PCB

RF PCB

- ARM 7 Processor

- Drivers

- SPI

- UART

- Timers

- Watchdog

- Discrete I/O

- Interrupts

28 Reciter Circuit Description TB8100 Service Manual

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.

TB8100 Service Manual Reciter Circuit Description 29

Figure 2.4 Reciter External Reference Block Diagram

10 or 12.8MHz

External Reference

Internal Reference

12.8MHz TCXO

Programmable

Reference Divider

Programmable

VCO Divider

Phase

Detector

Charge

Pump

fref

fVCOfb

Software

External Reference

Detector

Lock

Detect

RISC

8/9

Prescaler

Frequency Synthesizer IC

Loop

Filter

External Reference

12.8MHz VCO

Clock

Data

Chip Select/Latch Enable

Serial Bus

External

Reference

Buffer

12.8MHz VCXO

Feedback Buffer

Reference Switch

Ext_Ref_Det

Ext_Ref_Lock_Detect

Digital Switch

OFF / ON

ON / OFF

RF Switch

Ext_Ref_Ctrl

Buffer

FCL Reference

Receiver Synthesizer

Reference

Digital Clock

Synthesizer Reference

Internal/External Reference Clock Branch

30 Reciter Circuit Description TB8100 Service Manual

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.

TB8100 Service Manual Reciter Circuit Description 31

2.3 Receiver RF Circuitry

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.

Figure 2.5 Reciter Receiver RF Circuitry Block Diagram

Band Pass

Filter 1

Band Pass

Filter 2

Amplifier 1

Amplifier 2

Low Pass

Filter

Attenuator 6dB Pad

5dB

Pad

AGC Control AGC Detector

Mixer

Local Oscillator

Diplexer

Post-mixer

Buffer

Crystal

Filter

Amplifier

Anti-alias

Filter

IF Output

RF In

32 Reciter Circuit Description TB8100 Service Manual

Figure 2.6 Reciter Receiver Synthesizer Block Diagram

12.8MHz

Reference

Oscillator

Receiver VCO

Programmable

Reference Divider

Programmable

VCO Divider

Phase

Detector

Lock Detect

Output

Charge

Pump

fref

fVCOfb

Software

VCO Feedback

Attenuator

Lock Detect

Circuitry

64/65

Prescaler

Frequency Synthesizer IC

Loop

Filter VCO

LNA

Buffer

Harmonic

Filter

Fixed Slope

Attenuator Final

Driver

+20dBm LO

Clock

Data

Chip Select/Latch Enable

Serial Bus

TB8100 Service Manual Reciter Circuit Description 33

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.

34 Reciter Circuit Description TB8100 Service Manual

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

TB8100 Service Manual Reciter Circuit Description 35

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.

36 Reciter Circuit Description TB8100 Service Manual

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.

Figure 2.7 Comparison of VCXO and VCO Modulation Responses

VCXO VCO

150Hz

Gain

Frequency

3kHz

linear relationship

proportianal to the RF

frequency and

FCL_GAIN, measured

during calibration

non-linear relationship,

determined by

CalVcoGain_Corrected,

calculated from the

calibration data

TB8100 Service Manual Reciter Circuit Description 37

Figure 2.8 Reciter Exciter Synthesizer Modulator Block Diagram

ADC

DAC

Delay

Demodulator

VcoMod

Digitised Tx Audio

IntGain

DSP based FCL Processor

VcxoScale

TripleScale

PresTriDemod

FclFreqOffset (DC value)

FclMidPoint

(DC value)

Integrator

VcxoScale

Q Channel

I Channel

Divide by 4

LPF

FCL_I

FCL_Q

I-Q Exclusive OR Gate

Twisted Ring Counter

Digital Clock

Buffer

Digital Clock

Buffer

12.8MHz FCL

VCXO Oscillator

12.8MHz

Reference

Oscillator

VCXO Modulation

+ DC Offset

Exciter VCO

Programmable

Reference Divider

Programmable

VCO Divider

Digital Clock

Buffer

Phase

Detector

Charge

Pump

fref

fVCOfb

Software

VCO Feedback

Attenuator

Exciter Control

Circuit

64/65

Prescaler

Frequency Synthesizer IC

Loop

Filter

Varicap

Diodes

VCO

LNA

Buffer

Harmonic

Filter

Fixed Slope

Attenuator

10dB

Pad

Final

Driver

Fixed

Attenuator

+11dBm

to PA

Ex_Key

PA_Key

FCL_VCXO_CTRL

SYN_VCO_MOD

Frequency Control Loop

Clock

Data

Chip Select/Latch Enable

Serial Bus

Lock Detect

Output

Lock Detect

Circuitry

38 Reciter Circuit Description TB8100 Service Manual

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.

TB8100 Service Manual Reciter Circuit Description 39

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.

40 Reciter Circuit Description TB8100 Service Manual

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.

Note This section provides details on the system interface PCBs availa-

ble at the time of publication. Other types may be developed for

future applications.

System Interface PCB

Feature Standard Isolated

Isolated

E & M TaitNet

balanced audio 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 ✓✓✓✓

opto-coupled input ✓

opto-coupled output ✓

third-party connector ✓✓✓✓

TB8100 Service Manual Reciter Circuit Description 41

Connections to the

Reciter 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.

Figure 2.9 Reciter System Interface PCB Block Diagram

Power

Supply

Digital

Inputs

Digital

Outputs

Third-party

Connector

Mutes

SIPOs*

PISOs*

Conventional

Signalling

Interface

System Interface Identification

Third-party Audio

RSSIRSSI

Rx GateRx Gate

Tx KeyTx Key

Tx RelayTx Relay

Opto-coupled Output

Opto-coupled Input

Audio I/O

Digital Sub-system

Control

SIO BusSIO Bus

SIO Bus

Digipots

Third-party

I/O

Third-party

I/O

Third-party

I/O

Third-party

I/O

External Interface

Reciter Interface

Auxiliary

Power

Balanced Audio Input

Balanced Audio Output

Unbalanced Audio Input

Unbalanced Audio Output

*SIPO = Serial In, Parallel Out

PISO = Parallel In, Serial Out

# transformers not fitted to

standard system interface PCB

42 Reciter Circuit Description TB8100 Service Manual

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.

TB8100 Service Manual Reciter Circuit Description 43

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.

44 Reciter Circuit Description TB8100 Service Manual

Figure 2.10 Reciter Power Supply Block Diagram

Polyswitch

+ Zener

DSP Low

Regulator

2.5V

Lock-out

Circuit*

Regulator

3.3V

Regulator

Power

Switch

Power

Switches

Charge

Pump

Power

Switch

Power

Switch

Protection

Circuit

Linear 5V

Regulator

Dual SMPS

Regulator

Dual SMPS

Regulator

Comparators

Fan

Switch

Filter

Regulator

Filter

Regulator

Switch Filter

+28V

+28V 5.3V

8.5V 23V

8.5V to SIF

8VEX

8VRX

3.3V

PWD_EX

PWD_RX

PWD_ON

+28V

+28V SD

5.3V

3.3V

Control

PWR_GOOD

PWD_ON

PWD_RX

5V to SIF

Digital 5.3V

To Fan

+28V to RF PCB

RF PCB

Digital PCB

*To prevent DSP latch-up

SIF = system interface PCB

Analogue 5.3V

Analogue 5V

Analogue

System 5V

Digital 3.3V

Analogue 3.3V

2.5V

3.3V to SIF

TB8100 Service Manual Reciter Circuit Description 45

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.

46 Reciter Circuit Description TB8100 Service Manual

TB8100 Service Manual Reciter Circuit Description 47

Figure 2.11 Identifying the Circuitry on the Digital and System Interface PCBs

bsystem interface PCB

cCODECs

dSRAM

eRISC JTAG connector (factory use only)

fflash memory

gRISC

hDSP

iDSP JTAG connector (factory use only)

jmain digital system

1) power supply

1! digital IF and clock

1@ DDC

1# ADC

1$ 40MHz digital clock

1% 70.1MHz IF

1^ 12.8MHz reference

1& audio

1* high speed data connector

1( third-party connector

UHF (H band) reciter shown fitted

with isolated system interface PCB

48 Reciter Circuit Description TB8100 Service Manual

TB8100 Service Manual Reciter Circuit Description 49

Figure 2.12 Identifying the Circuitry on the RF PCB

bexternal reference input

cmixer and post-mixer buffer

dreceiver VCO

ereceiver VCO trimmer

fIF tuning elements

greceiver synthesizer

hIF

iTCXO

jaudio buffers

1) exciter VCO

1! exciter VCO trimmer

1@ exciter synthesizer

1# exciter RF output

1$ FCL

1% FCL buffers

1^ power supply

1& external reference switch/internal VCXO reference

1* AGC

1( front end 1

2) front end first helicals

2! front end 2

2@ front end second helicals

2# receiver RF input

Note:

In order to show as much of the circuitry as possible in the

photograph, the SMD shields have been removed.

UHF (H band) reciter shown

50 Reciter Circuit Description TB8100 Service Manual

TB8100 Service Manual Reciter Servicing 51

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 For the sake of simplicity and clarity, the instructions and illustra-

tions in this chapter refer to a UHF (H band) reciter fitted with an

isolated system interface PCB. However, the same basic proce-

dures and techniques apply to other models of reciter and system

interface PCB.

52 Reciter Servicing TB8100 Service Manual

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 sug-

gest 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

a. The actual frequency coverage in this band is:

Transmit: 762MHz to 776MHz, and 850MHz to 870MHz

Receive: 792MHz to 824MHz

TBA4XXX-XXXXSystem Interface PCB

000 = no system interface PCB fitted

0A0 = standard

0B0 = isolated

0C0 = isolated E & M

0T1 = TaitNet

TBA4XXX-XXXX0 = default

TB8100 Service Manual Reciter Servicing 53

Figure 3.1 Identifying the Reciter PCBs

digital PCB

UHF (H band) reciter shown

fitted with isolated system

interface PCB; RF PCB shown

with shields removed for clarity

system interface PCBRF PCB

54 Reciter Servicing TB8100 Service Manual

Screw Torque Settings

The recommended torque settings for the screws and nuts used in the reciter

are as follows:

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.

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.

Location / Function Torque Driver/

Spanner Size

■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

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

TB8100 Service Manual Reciter Servicing 55

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.

Figure 3.2 Removing the Front and Rear Panels

front view rear view

RF side

RF sidedigital side

h2 for each

rear panel

56 Reciter Servicing TB8100 Service Manual

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 The covers are not interchangeable. Each cover must be fitted to

the correct side and in the correct orientation.

3.2 Replacing the Digital PCB

Important You must reprogram and recalibrate the reciter after replac-

ing the digital PCB. Refer to “Reprogramming and Rec-

alibration” 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 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 Reciter Servicing 57

Figure 3.3 Replacing the Digital and System Interface PCBs

58 Reciter Servicing TB8100 Service Manual

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 insula-

tor, 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 Before tightening the screws, press the PCB down over the locat-

ing 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.

Figure 3.4 Reconnecting the Flexible Connectors

flexible connector inserted

straight into socket

blue stripe on same

side as latch

latch pushed fully down

at both ends

TB8100 Service Manual Reciter Servicing 59

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.

3.3 Replacing the System Interface PCB

Important You must reprogram and recalibrate the reciter after replac-

ing 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.

Procedure 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

60 Reciter Servicing TB8100 Service Manual

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 insula-

tor, 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 Before tightening the screws, press the PCB down over the locat-

ing 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.

Reprogramming

and Recalibration 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.

PCB Type Procedure Details

when the replacement

system interface PCB is

a different type from

the original

■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

calibrate the audio carry out this procedure using the Calibration

Kit software; refer to the Calibration Kit

documentation for more details

when the replacement

system interface PCB is

the same type as the

original

calibrate the audio carry out this procedure using the Calibration

Kit software; refer to the Calibration Kit

documentation for more details

TB8100 Service Manual Reciter Servicing 61

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 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.

Refitting 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 Before tightening the screws, press the PCB down over the locat-

ing 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.

62 Reciter Servicing TB8100 Service Manual

Figure 3.5 Replacing the RF PCB

TB8100 Service Manual Reciter Servicing 63

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 Details

■calibrate the exciter

■calibrate the RSSI

■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

64 Reciter Servicing TB8100 Service Manual

TB8100 Service Manual Reciter Servicing 65

Figure 3.6 Reciter Mechanical Assembly

Description IPN

b70.1MHz IF and 12.8MHz reference coaxial cables 219-02849-XX

cflexible connector 219-02850-XX

dRF input coaxial cable 219-02851-XX

eexternal reference coaxial cable 219-02852-XX

fSMA connector 240-02155-XX

gvent guard clip 303-50108-XX

hhandle 308-01065-XX

iheatsink 308-13148-XX

jRF side cover 316-06795-XX

1) front panel 316-06796-XX

1! digital side cover 316-06797-XX

1@ rear panel - digital side; changes according to the

system interface PCB fitted:

standard, isolated, isolated E & M

Tai tN e t

none

316-06798-XX

316-06799-XX

316-06802-XX

1# fan duct 316-06804-XX

1$ rear panel - RF side 316-06805-XX

1% M3x6mm countersunk Torx screw 345-40460-XX

1^ M3x8mm pan head Torx screw with spring & flat

washers

345-40470-XX

1& M2.5x8mm pan head Torx screw 345-40490-XX

1* M3x12mm pan head Torx Taptite screw 349-02065-XX

1( 4–40 UNC screw lock 354-01043-XX

2) thermally conductive insulator sheet 362-01120-XX

2! RF PCB

2@ digital PCB

2# system interface 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.

x14

x16

x11

x24

66 Reciter Servicing TB8100 Service Manual

TB8100 Service Manual Power Amplifier Circuit Description 67

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.

Figure 4.1 PA High Level Block Diagram

PCB

Control PCB

60W

PCB

60W

PCB

Ambient Air

Temperature

Sensor

PCB

Splitter

PCB

Combiner

PCB

Low-Pass

Filter

Directional

Coupler

PCB

RF I/P +

PA Key RF O/P

28VDC

I/P

RF RF RF RF

RF RF

Control &

Monitor

Control &

Monitor

Control &

Monitor

System

Control

Bus

68 Power Amplifier Circuit Description TB8100 Service Manual

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 60 W 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.

TB8100 Service Manual Power Amplifier Circuit Description 69

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:

1. The accuracy of the measurement of the parameter values is subject to the

tolerances listed in the Specifications Manual.

Model Pmin

5W 1W

50W 5W

100W 10W

70 Power Amplifier Circuit Description TB8100 Service Manual

Figure 4.2 PA Control, RF and Power Supply Circuitry Block Diagram

60W

High Pass

Filter

Directional

Coupler

Low Pass

Filter

Attenuator

100mW

Gain Block

Final

6W PCB

Control PCB

LPF/Directional Coupler PCB

Microprocessor

60W

PCB

60W

PCB

Combiner

PCB

Splitter

PCB

Driver

Load

Ω50

Load

Ω

Pre-driver

RF In RF Out

Block

Detect

DACDACDACDACDAC

ADCADC ADC ADC ADC ADC ADC

AND

power control

driver current

driver temperature

final 2 drive current

final 1 drive current

driver bias

final 2 bias

final 2 temperature

final 1 temperature

final 1 bias

RF power setting

transient wave shape

forward power

reverse power

ambient air temperature

+10V Power

Supply

+5V Power

Supply

Fan

Buffer

-3V Power

Supply

+2.5V Power

Supply

+10V

-3V

PA_KEY I C

System

Control

Bus

+28V

60W

Final

+28V

This drawing shows the

circuitry for the 100W PA.

TB8100 Service Manual Power Amplifier Circuit Description 71

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:

The forward power, reverse power and load VSWR measurements may also

be requested via I2C bus messages.

Model Output Power Range

5W 1 to 5W

50W 5 to 50W

100W 10 to 100W

72 Power Amplifier Circuit Description TB8100 Service Manual

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

TB8100 Service Manual Power Amplifier Circuit Description 73

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 You must fit the sensor PCB in the correct location to ensure that

the temperature of the airflow over the sensor is nearest the ambi-

ent 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.

4.2 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.

74 Power Amplifier Circuit Description TB8100 Service Manual

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.

TB8100 Service Manual Power Amplifier Circuit Description 75

Figure 4.3 Identifying the Circuitry on the PA PCBs

bRF output

clow pass filter/directional coupler PCB

ddirectional coupler

elow pass filter

fcontrol PCB

gpower supply

hambient air temperature PCB

i28VDC power feed

j60W PCB

1) microprocessor

1! 6W PCB temperature sense

1@ 6W driver transistor drain current sense

1# I2C signal filtering

1$ RF input (obscured)

1% 28VDC input

1^ 6W PCB

1& pre-driver transistor

1* 6W driver transistor

1( termination resistor (50Ω load)

2) splitter PCB

2! 60W PCB temperature sense

2@ 60W final transistor

2# 60W PCB

2$ 60W final transistor drain current sense

2% combiner PCB

2^ termination resistor (50Ω load)

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.

76 Power Amplifier Circuit Description TB8100 Service Manual

TB8100 Service Manual Power Amplifier Servicing 77

5 Power Amplifier Servicing

Caution The termination resistors used in the 100W power

amplifier contain some beryllium oxide. This sub-

stance 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 termina-

tion 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 accord-

ing 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 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.

78 Power Amplifier Servicing TB8100 Service Manual

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

a. The actual frequency coverage in this band is 762MHz to 776MHz, and 850MHz to

870MHz.

TBAXXXX-XXXX 0 = default

TBAXXXX-XXXX0 = default

TB8100 Service Manual Power Amplifier Servicing 79

Figure 5.1 Identifying the PA PCBs

b6W PCB g5W interconnect PCB

c60W PCB h50W interconnect PCB

dlow pass filter/directional coupler PCB isplitter PCB

econtrol PCB jcombiner PCB

fambient air temperature sensor PCB

5W PA

50W PA

100W PA

under

shield

under

shield

h c

80 Power Amplifier Servicing TB8100 Service Manual

Screw Torque Settings

The recommended torque settings for the screws used in the PA are as

follows:

Removing the Airflow Duct and Cover

The circled numbers in the following instructions refer to Figure 5.2.

Airflow Duct

(100W PA Only) 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.

Cover 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.

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.

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

TB8100 Service Manual Power Amplifier Servicing 81

Figure 5.2 Removing the Airflow Duct, Cover and Front Panel

x3 on other side

82 Power Amplifier Servicing TB8100 Service Manual

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.

Note Fit the two screws d securing the N-type connector to the cover

first, followed by the screws securing the cover to the heatsink.

Airflow Duct

(100W PA Only) 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

To r x s c r e w b.

TB8100 Service Manual Power Amplifier Servicing 83

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.

5.3 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 pre-

vent 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 Cali-

bration 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.

Figure 5.3 PCB Connecting Links

84 Power Amplifier Servicing TB8100 Service Manual

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.

Refitting 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 Before tightening the screws, press the PCB down over the locat-

ing pins so that it is firmly seated against the heatsink. Then

tighten the M3 Torx screws to the correct torque.

4. Refit the front panel and cover.

Figure 5.4 Replacing the 6W PCB

TB8100 Service Manual Power Amplifier Servicing 85

5.4 Replacing the 60W PCB

Important There is heatsink compound between the RF power tran-

sistor 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 Cali-

bration 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 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.

Refitting the Same

PCB and Transistor 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 Before tightening the screws, press the PCB down over the locat-

ing pins so that it is firmly seated against the heatsink. Then

tighten the M3 Torx screws to the correct torque.

86 Power Amplifier Servicing TB8100 Service Manual

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.

Refitting a New PCB

and Transistor 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 Before tightening the screws, press the PCB down over the locat-

ing 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.

Figure 5.5 Replacing the 60W PCB

TB8100 Service Manual Power Amplifier Servicing 87

5.5 Replacing the 60W RF Power Transistor

Important If you do not follow these procedures correctly, the transis-

tor 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 resist-

ance. To avoid possible damage to the device during han-

dling, testing or actual operation, we recommend you fol-

low 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-conduc-

tive 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 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.

Refitting 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

88 Power Amplifier Servicing TB8100 Service Manual

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 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.

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 Replacing the 60W RF Power Transistor

db c

TB8100 Service Manual Power Amplifier Servicing 89

5.6 Replacing the Control PCB

Important You must reprogram and recalibrate the PA after replacing

the control PCB. Refer to “Reprogramming and Recali-

bration” 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 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.

Refitting 1. To refit the PCB, follow the removal instructions in reverse order.

Important 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 temper-

ature 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.

Note Before tightening the screws, press the PCB down over the locat-

ing pins so that it is firmly seated against the heatsink. Then

tighten the M3 Torx screws to the correct torque.

90 Power Amplifier Servicing TB8100 Service Manual

Reprogramming

and Recalibration If you have replaced the control PCB, you will have to reprogram and

recalibrate the PA as described in the table below.

Figure 5.7 Replacing the Control PCB

d f

100W PA

5/50W PA

Procedure Details

■reprogram the product code

■reprogram the PA type

reprogram this information into the PA using

the Calibration Kit software; refer to the

Calibration Kit documentation for more

details

replace the serial number labels 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

■calibrate the stage bias

■calibrate the forward and reverse

detector bias voltages

■calibrate the PA output power

carry out these procedures using the

Calibration Kit software; refer to the

Calibration Kit documentation for more

details

TB8100 Service Manual Power Amplifier Servicing 91

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 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.

Refitting 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:

■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.

92 Power Amplifier Servicing TB8100 Service Manual

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 cor-

rectly.

4. Replace the RF links c and bridging links b.

5. Refit the shield lid and resolder the two tabs.

6. Refit the cover.

Note 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 cut-

ting tool (such as tin snips or a guillotine).

5.8 Replacing the Interconnect PCBs

Refer to Section 5.1 “Disassembly and Reassembly” for details on removing

and refitting the cover.

Removal 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.

Figure 5.8 Replacing the LPF/Directional Coupler PCB

100W PA 5W and 50W PA

TB8100 Service Manual Power Amplifier Servicing 93

4. Carefully lift the PCB directly upwards off the locating pins and

remove it from the heatsink.

Refitting 1. To refit the PCB, follow the removal instructions in reverse order.

Note Before tightening the screws, press the PCB down over the locat-

ing pins so that it is firmly seated against the heatsink. Then

tighten the M3 Torx screws to the correct torque.

5.9 Replacing the Splitter/Combiner PCBs

Important There is heatsink compound between the termination resis-

tors 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 com-

ponents 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.

94 Power Amplifier Servicing TB8100 Service Manual

7. Carefully lift the PCB directly upwards off the locating pins f and

remove it from the heatsink.

Refitting 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.

Figure 5.9 Replacing the Splitter/Combiner PCBs

Splitter Combiner

eecd

TB8100 Service Manual Power Amplifier Servicing 95

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.

96 Power Amplifier Servicing TB8100 Service Manual

TB8100 Service Manual Power Amplifier Servicing 97

Figure 5.10 PA Mechanical Assembly - Sheet 1

Description IPN

bDC input feedthrough capacitor 012-04100-07

cDC power link 051-00640-XX

dDC input cable - 5/50W

DC input cable - 100W

219-02854-XX

219-02855-XX

ebridging links 240-00020-61

fN-type connector 240-02100-64

gSMA connector 240-02155-20

hP-clip 303-50107-XX

ihandle 308-01065-XX

jheatsink - 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! LPF/directional coupler shield lid 319-01247-XX

1@ N-type connector ground plate 319-01249-XX

1# LPF/directional coupler shield lid spring contacts 319-01259-XX

1$ M3x6mm countersunk Torx screw 345-40460-XX

1% M3x8mm pan head Torx screw + spring/flat washers 345-40470-XX

1^ M2.5x8mm pan head Torx screw 345-40490-XX

1& M3x10mm pan head Torx Taptite screw 349-02066-XX

1* 4–40x5/16 UNC Allen recess head screw 349-20460-XX

1( 3mm solder tag - short 356-00010-01

2) 3mm solder tag - long 356-00010-03

2! 4mm right-angle solder tag 356-00010-74

2@ RF link 356-01080-XX

2# ground tag for 60W RF power transistor 356-01081-XX

2$ metal strap for feedthrough capacitor 356-01082-XX

2% insulating washer for feedthrough capacitor 362-00010-51

2^ dust seal for ambient air temperature sensor PCB 362-01036-XX

2& control PCB

2* 6W PCB

2( LPF/directional coupler PCB

3) 60W PCB

3! ambient air temperature sensor PCB

3@ combiner PCB

3# splitter PCB

3$ bridging link PCB

50W interconnect PCB*

5W interconnect PCB*

*Not shown in this drawing. Refer to Figure 5.1 on

page 79.

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:

This drawing shows a 100W PA. Any differences

between the 100W, 5W and 50W PAs are indicated in

the description of the parts.

g2^

3! 2@

1*1(

x3 each side

x5 100W

x4 5/50W

98 Power Amplifier Servicing TB8100 Service Manual

Figure 5.11 PA Mechanical Assembly - Sheet 2

Description IPN

bcover - 5/50W

cover - 100W

303-03070-XX

303-03071-XX

cP-clip 303-50107-XX

dairflow duct centre panel 316-06818-XX

eairflow duct side panel 316-06819-XX

fM3x6mm countersunk Torx screw 345-40460-XX

gM3x10mm pan head Torx Taptite screw 349-02066-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.

x26 100W

x24 5/50W

x3 each side

TB8100 Service Manual Power Management Unit Circuit Description 99

6Power 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).

100 Power Management Unit Circuit Description TB8100 Service Manual

Figure 6.1 PMU High Level Block Diagram

PFC

Circuitry

PFC

Control

Card

DC Input

Filter

Card

Control

Card

Auxiliary

Power Supply

PCB*

Battery

Control

Card

Standby

Power Supply

Card*

HVDC Control &

Microprocessor

Card

HVDC Circuitry

DC Converter PCB

28V

28V O/P (PA)

System

Control Bus

28V O/P (Reciter)

AC I/P

115/230V

50/60Hz 400VDC

DC I/P

12V

28V 13.8V O/P

*optional

AC Converter PCB

AC Module

DC Module

DC I/P

12/24/48V

DC O/P

13.65/27.3/54.6V

TB8100 Service Manual Power Management Unit Circuit Description 101

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.

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 cardaoptional optional

AC converter PCB fitted fittedbfitted

HVDC control and microprocessor card fitted fittedcfitted

PFC control card fitted fitted

auxiliary power supply PCBdoptional 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).

102 Power Management Unit Circuit Description TB8100 Service Manual

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.

Figure 6.2 PMU Microprocessor Functional Block Diagram

5V Supply

Flash

Programming

Supply

Converter

Auxiliary

Power

Supply*

Microprocessor

Temperature

28V

Data

Run

Voltage Sense

Current Sense

Fan

Current Sense

Microprocessor

Supply

Temperature

Mains

Input

Output

Reciter

Output

Auxiliary

Output

Battery

Input Battery

Supply

On/Off

Standby

Power

Supply*

Hysteresis Mode

Shutdown

Standby Supply

Present

Low Battery

Alarm On

*optional

Summary

Alarm On

Vpp

Vpp Enable

Fan Supply On

I C

2Signals

Fan

Output

Summary Alarm

Output

Low Battery

Alarm Output

I C Port

Run

Data

Standby Supply Isolate

Mains OK

Shutdown

1. A type of “sleep” mode available when the standby power supply card is not

fitted.

TB8100 Service Manual Power Management Unit Circuit Description 103

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.

104 Power Management Unit Circuit Description TB8100 Service Manual

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.

EMC Filter,

Protection, and AC

Switch

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

Figure 6.3 PMU AC Module Block Diagram

EMC Filter,

Protection,

& AC Switch

Power Factor

Correction

(PFC)

High Voltage

to DC

(HVDC)

System

Interface

and

Fan Control

PFC Control HVDC Control

Current Sense

and

Output Filter

Interface to

DC Module Microprocessor

AC I/P

115/230V

50/60Hz

Control &

Monitor

28VDC O/P

(PA)

28VDC O/P

(Reciter)

System

Control Bus

Fan

TB8100 Service Manual Power Management Unit Circuit Description 105

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 opto-

coupler 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.

106 Power Management Unit Circuit Description TB8100 Service Manual

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 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.

6.3 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 PMU DC Module Block Diagram

EMC Filter

and

Protection

DC Power

Converter

(DCDC)

DC Control

Battery

Control

Standby

Power

Supply*

Auxiliary

Power

Supply*

Interface to

AC Module

DC I/P

12/24/48V

Control &

Monitor

*optional

DC O/P

13.65/27.3/54.6V

TB8100 Service Manual Power Management Unit Circuit Description 107

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.

108 Power Management Unit Circuit Description TB8100 Service Manual

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 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.

TB8100 Service Manual Power Management Unit Circuit Description 109

Figure 6.5 Identifying the Circuitry on the AC Module PCBs

bEMC filter, protection and AC switch

cpower factor correction (PFC)

dPFC control

ehigh voltage to DC converter

f28VDC input from the DC converter PCB

gcurrent sense and output filter

h28VDC output for PA

i28VDC output for reciter

j28VDC output to auxiliary power supply PCB

1) microprocessor control

1! AC and DC voltage and current control

1@ HVDC control

1# fuse (10A 250V)

1$ 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.

110 Power Management Unit Circuit Description TB8100 Service Manual

TB8100 Service Manual Power Management Unit Circuit Description 111

Figure 6.6 Identifying the Circuitry on the DC Module PCBs

bDC input

cauxiliary power supply

dDC power converter

eDC control

foutput to the current sense and output filter circuitry on the

AC converter PCB

gbattery control

hcurrent transformer

istandby power supply

jEMC 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.

12V DC module shown

112 Power Management Unit Circuit Description TB8100 Service Manual

TB8100 Service Manual Power Management Unit Servicing 113

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 operat-

ing. 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.

114 Power Management Unit Servicing TB8100 Service Manual

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 resist-

ance. To avoid possible damage to the device during han-

dling, testing or actual operation, we recommend you fol-

low 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-conduc-

tive 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.

TB8100 Service Manual Power Management Unit Servicing 115

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.

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 For the sake of simplicity and clarity, the instructions and illustra-

tions 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.

Part/Assembly

PMU Configuration

AC PMU DC PMU AC and DC PMU

AC module standard module fitted AC converter PCB is mounted on

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

standard module fitted

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

116 Power Management Unit Servicing TB8100 Service Manual

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 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-XXXX0 = default

TB8100 Service Manual Power Management Unit Servicing 117

Figure 7.1 Identifying the PMU PCBs

standby power supply card

battery control card

auxiliary power supply PCB

DC converter PCB

PFC control card

AC converter PCB

DC converter PCB

HVDC control and

microprocessor card

DC control card

bottom view

top view

AC and DC PMU shown

118 Power Management Unit Servicing TB8100 Service Manual

Screw Torque Settings

The recommended torque settings for the screws used in the PMU are as

follows:

Removing the Top and Bottom Covers

1. Remove the four M3 Torx screws securing the top cover to the front

and rear panels. Lift off the top cover.

Note 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.

2. 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

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.

Location / Function Torque Driver Size

■securing the front and rear panels to

the heatsinks

■securing the AC and DC converter

PCBs to the heatsinks

■securing the bus bars to the DC

converter PCB

2.0N·m / 18lbf·in T20 M4

■securing the top and bottom covers

to the front and rear panels

■securing the handle to the front

panel

■securing the DC input filter card to

the bus bars

0.5N·m / 4.5lbf·in T10 M3

securing the 500W DC transformer

primary wires into their terminals

1.8N·m / 16lbf·in flat blade

TB8100 Service Manual Power Management Unit Servicing 119

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 rib-

bon 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 These connectors have locking tabs. You must disengage the

locking tab before you can remove the plug from the socket.

5. 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 rib-

bon 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.

120 Power Management Unit Servicing TB8100 Service Manual

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.

Figure 7.2 Disconnecting the AC and DC Modules

AC module DC module

bcddfe

TB8100 Service Manual Power Management Unit Servicing 121

Figure 7.3 Reconnecting the AC and DC Modules

122 Power Management Unit Servicing TB8100 Service Manual

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 respec-

tive 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 Before fully tightening the

screws, make sure that all con-

nectors, switches and the fibre-

glass insulator are correctly

located in their respective holes

in the panel.

7. Refit and tighten the M4 Torx Taptite screw securing the rear panel

to the AC converter PCB.

Refitting the Top and Bottom Covers

1. Refit the bottom cover over the front and rear panels and secure with

the four M3 Torx screws.

Note 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.

2. 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.

TB8100 Service Manual Power Management Unit Servicing 123

3. Push the top cover down firmly and secure with the four M3 Torx

screws.

Note Both the top and bottom covers are symmetrical and can be fitted

in either orientation.

7.3 Replacing the Plug-in Cards

Important You must reprogram the PMU if you fit a replacement

HVDC and microprocessor card, or change the configura-

tion 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 mod-

ule 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 sup-

ply card must match the DC input voltage of the DC mod-

ule (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.

124 Power Management Unit Servicing TB8100 Service Manual

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.

Figure 7.4 Replacing the Plug-in Cards

TB8100 Service Manual Power Management Unit Servicing 125

Removal - Method 2 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.

Refitting 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.

Reprogramming If you have replaced the HVDC and microprocessor card, you will have to

reprogram the PMU as described in the table below.

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.

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

126 Power Management Unit Servicing TB8100 Service Manual

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 configura-

tion 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.

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

Figure 7.5 Replacing the Auxiliary Power Supply PCB

TB8100 Service Manual Power Management Unit Servicing 127

Removal 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.

Refitting 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.

Reprogramming 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.

There is no need for any recalibration when this PCB is fitted, removed or

replaced.

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

128 Power Management Unit Servicing TB8100 Service Manual

TB8100 Service Manual Power Management Unit Servicing 129

Figure 7.6 PMU Mechanical Assembly - Sheet 1

Description IPN

bcurrent transformer 053-00028-XX

cE-core choke 069-00010-40

dclamp for E-core choke 069-00010-41

eAC mains input connector 219-02843-XX

fE-core choke PCB 220-02023-XX

g4mm bus bar terminal 240-04030-44

hretaining clip (holds device against heatsink) 303-50040-XX

ihandle 308-01065-XX

jheatsink 308-13146-XX

1) heatsink insulator 309-01051-XX

1! DC input insulator 309-01052-XX

1@ bottom cover 316-06811-XX

1# front panel 316-06812-XX

1$ rear panel 316-06813-XX

1% top cover 316-06814-XX

1^ shield 319-01246-XX

1& M6x12mm pan head Pozidriv screw 345-00070-05

1* M3x6mm countersunk Torx screw 345-40460-XX

1( M3x8mm pan head Torx Taptite screw 349-00020-36

2) M4x12mm pan head Torx Taptite screw 349-02058-XX

2! M3x10mm pan head Torx Taptite screw 349-02066-XX

2@ wire retaining clip (if 40W aux. PS PCB fitted) 357-01051-XX

2# plastic grommet 360-02026-XX

2$ M3 T03 insulator bush 362-00010-11

2% 10mm ID insulator bush with shoulder 362-00011-XX

2^ seal (when 40W aux. PS PCB not fitted) 362-01122-XX

2& AC converter PCB

2* PFC control card

2( HVDC control and microprocessor card

3) DC converter PCB

3! DC input filter card

3@ DC control card

3# battery control card

Not Shown in this Drawing

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

thermally conductive insulator sheet 16x22mm 362-01116-XX

thermally conductive insulator sheet 130x22mm 362-01117-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:

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.

2# 1^

1# 2@

jc3)

x7 each

module

x5 each end

gx3

x2 per

transformer

x1 per

heatsink

130 Power Management Unit Servicing TB8100 Service Manual

Figure 7.7 PMU Mechanical Assembly - Sheet 2

Description IPN

DC PMU

bAC converter PCB mounting bracket 302-05268-XX

cheatsink insulator 309-01051-XX

dM4x12mm pan head Torx Taptite screw 349-02058-XX

eAC converter PCB (current sense and output filter

circuitry only)

fPFC control card

gHVDC control and microprocessor card (feedback and

microprocessor circuitry only)

AC PMU

hDC input insulator 309-01052-XX

irear panel 316-06813-XX

jAC blanking plate 316-06836-XX

1) M4x12mm pan head Torx Taptite screw 349-02058-XX

1! seal (when 40W aux. PS PCB not fitted) 362-01122-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.

DC PMU

This drawing shows the assembly of the

AC module when it is fitted to a DC PMU.

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.

x4 each end

each end

TB8100 Service Manual Control Panel Circuit Description 131

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.

1. For a description of the controls located on the control panel, refer to

“Operating Controls” in the Installation and Operation Manual.

Control Panel PCB

Feature Standard Power Save

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 ■

132 Control Panel Circuit Description TB8100 Service Manual

Figure 8.1 Control Panel High Level Block Diagrams

Translation

RS-232

Translation

Microphone

Pre-emphasis

& Gain Control

Speaker

Volume &

Gain Control

LEDs &

Switches

Control

Panel Type

Microphone

Connector

Speaker

Fan Inputs

RS-232

Connector

Power

Supply

Microphone Audio

System

Control Bus

Speaker

Enable

Speaker Audio

I C Bus

28V, GND

Fan Power & GND

Open Collector RS-232 RS-232 Bus

Translation

RS-232

Translation

LEDs

Control

Panel Type

Fan Inputs

RS-232

Connector

Power

Supply

System

Control Bus

Full Power On

Power Save On

I C Bus

28V, GND

Fan Power & GND

Open Collector RS-232 RS-232 Bus

Standard Control Panel

Power Save Control Panel

TB8100 Service Manual Control Panel Circuit Description 133

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.

134 Control Panel Circuit Description TB8100 Service Manual

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.

TB8100 Service Manual Control Panel Servicing 135

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 For the sake of simplicity and clarity, the instructions and illustra-

tions in this chapter refer to a standard control panel. However,

the same basic procedures and techniques apply to other models.

136 Control Panel Servicing TB8100 Service Manual

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.

9.2 Screw Torque Settings

The recommended torque settings for the screws and nuts used in the

control panel are as follows:

9.3 Replacing the PCB

The circled numbers in the following instructions refer to Figure 9.1.

Removal 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.

Product Code Description

TBA201X power save

TBA202X standard

Location / Function Torque Driver/

Spanner Size

■securing the PCB

■securing the D-range connector

0.5N·m / 4.5lbf·in T10 M3

securing the speaker clamps 0.5N·m / 4.5lbf·in 5.5mm AF M3

TB8100 Service Manual Control Panel Servicing 137

Figure 9.1 Replacing the Control Panel PCB

138 Control Panel Servicing TB8100 Service Manual

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 Make sure the flexible connector is correctly positioned and

latched in its socket, as shown in Figure 9.2.

5. Refit the volume knob.

Figure 9.2 Reconnecting the Flexible Connector

flexible connector inserted

straight into socket

latch pushed fully down

at both ends

TB8100 Service Manual Control Panel Servicing 139

9.4 Replacing the Speaker

The circled numbers in the following instructions refer to Figure 9.3.

Removal 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.

Refitting 1. To refit the speaker, follow the removal instructions in reverse order.

Tighten the M3 nuts to the correct torque.

Important 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).

2. Refit the PCB as described in “Replacing the PCB” on page 136.

Figure 9.3 Replacing the Speaker

140 Control Panel Servicing TB8100 Service Manual

TB8100 Service Manual Control Panel Servicing 141

Figure 9.4 Control Panel Mechanical Assembly

Description IPN

bD-range to Micromatch ribbon cable 219-02853-XX

cspeaker* 252-00011-XX

dspeaker mounting bracket* 302-05266-XX

espeaker grille cloth* 307-01024-XX

fvolume knob* 311-01054-XX

gkeypad - standard

keypad - power save

311-03116-XX

311-03115-XX

hchassis 316-06820-XX

iM3x8mm pan head Torx screw with spring & flat

washers

345-40470-XX

jM3 hex nut* 352-00010-08

1) 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.

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

dx2

ix4

jx2

1) x2

ix2

142 Control Panel Servicing TB8100 Service Manual

TB8100 Service Manual Subrack Servicing 143

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.

144 Subrack Servicing TB8100 Service Manual

TB8100 Service Manual Subrack Servicing 145

Figure 10.1 Front Panel Mechanical Assembly

Description IPN

bfan contact PCB 220-02028-XX

cfan:

no rotation sensor

rotation sensor

258-00011-XX

258-00014-XX

dPA fan duct 302-05264-XX

ePMU fan duct 302-05265-XX

fspring clip 303-50106-XX

gfront panel 316-06821-XX

hKC30x10mm pan head Torx PT screw 346-10030-10

iM4x40mm pan flange head Torx PT screw 346-10440-XX

jquarter-turn fastener 354-01047-XX

1) retaining washer for quarter-turn fastener 354-01048-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:

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.

146 Subrack Servicing TB8100 Service Manual

Figure 10.2 Subrack Mechanical Assembly

Description IPN

bmodule retaining clamp 303-50102-XX

ccable retaining clip 303-50104-XX

dbottom guide rail 307-02052-XX

etop guide rail (also used in the bottom corners

when required)

307-02053-XX

frear blanking panel 316-06785-XX

gsubrack 318-01051-XX

hM4x10mm pan head Pozidriv screw 345-00050-07

iM3 hex nut 352-00010-08

jM3 spring washer 353-00010-12

1) receptacle for quarter-turn fastener 354-01049-XX

1! subrack ground connector 356-00010-61

1@ 9.5mm P-clip 357-00010-48

1# insulating foam 362-01037-XX

1$ insulator for interconnect PCB 362-01121-XX

1% 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.

TB8100 Service Manual Subrack Servicing 147

Figure 10.3 Cable Identification

Description IPN

bRF coaxial cable - reciter to 5/50W PA (long) 219-02859-XX

cRF coaxial cable - reciter to 5/50W PA (short) 219-02862-XX

dRF coaxial cable - reciter to 100W PA 219-02864-XX

esystem control bus ribbon cable - reciter to subrack

interconnect PCB

219-02858-XX

fsystem control bus ribbon cable - 5/50W PA to

subrack interconnect PCB

219-02861-XX

gsystem control bus ribbon cable - PMU and 5/50W

PA to subrack interconnect PCB

219-02857-XX

hsystem control bus ribbon cable - PMU and 100W

PA to subrack interconnect PCB

219-02863-XX

iDC power cable - PMU to single reciter 219-02856-XX

jDC power cable - PMU to dual reciters 219-02860-XX

1) DC power cable - PMU aux. output to single reciter

DC power cable - PMU aux. output to dual reciters

219-02895-XX

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.

dual 5/50W BSS - front view

single 100W BSS - front view

dual 5/50W BSS - rear view

148 Subrack Servicing TB8100 Service Manual

TB8100 Service Manual Glossary 149

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.

A B C D E F G H I K L N P R S T U V W

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.

150 Glossary TB8100 Service Manual

anti-kerchunking Anti-kerchunking is a base station configuration that discourages users from

kerchunking.

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.

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.

TB8100 Service Manual Glossary 151

CODEC An IC which combines analog-to-digital conversion (coding) and digital-

to-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.

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.

152 Glossary TB8100 Service Manual

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.

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.

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.

gating Gating is the process of opening and closing the receiver gate. When a valid

signal is received, the receiver gate opens.

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,

TB8100 Service Manual Glossary 153

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.

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.

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.

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.

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.

154 Glossary TB8100 Service Manual

operating range Operating range is another term for switching range.

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.

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.

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-

TB8100 Service Manual Glossary 155

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.

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.

Tas k M a na ge r 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.

156 Glossary TB8100 Service Manual

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.

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.

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.

Watchdog 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 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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