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2.6

Circuit Operation

M889-00

02/10/95

Copyright TEL

2.3.5

Forward And Reverse Power Metering

Forward and reverse power signals from the two IC3 buffers are available for metering
purposes. The output currents are adjustable via RV43 (forward power) and RV57
(reverse power).

2.3.6

Fan Control Circuitry

Figure 2.3 Fan Control Logic Diagram

Comparator IC3 pins 8, 9 & 10 are set to trigger at heatsink temperatures greater than
+70

°

C, and pins 12, 13 & 14 at temperatures greater than -10

°

C.

A logic AND function is applied to the comparator outputs by Q20 and Q21, thereby
turning on the fan unconditionally (via Q17 and Q18) if the heatsink temperature
e70

°

C.

A logic OR function is applied to comparator IC3 pins 8, 9 & 10 and Tx KEY signals,
thereby turning on the fan when the transmitter is keyed and the temperature is
between -10

°

C and +70

°

C.

If the temperature drops below -10

°

C, Q21 is turned off, preventing either Q19 or Q20

from activating the fan.

Q17 Q18

Fan

Ref

+

High Temp.

Sense

Comparator

IC3C

R72

Ref

+

Low Temp.

Sense

Comparator

IC3D

R116

NTC

NTC

Tx Key

Invert

Q19

OR

Q20,

R106, R107

NAND

Q20, Q21,

R119, R120

Fan Driver

13.8V

Filtered

«
...
16
17
18
19
20
...
»

Summary of Contents for T889

Page 1: ...M889 00 1 Copyright TEL 02 10 95 T889 Power Amplifier UHF FM 800 870MHz Issue 100 October 1995 M889 00 100 ...

Page 2: ...rie 92 316 Sèvres Cedex France Phone 33 1 41 14 05 50 Fax 33 1 41 14 05 55 Germany Tait Mobilfunk GmbH Willstätterstraße 50 D 90449 Nürnberg 60 Germany Phone 49 911 96 746 0 Fax 49 911 96 746 79 New Zealand Tait Communications Ltd Unit 4 75 Blenheim Road P O Box 1185 Christchurch Phone 64 3 348 3301 Fax 64 3 343 0558 Singapore Tait Electronics Far East Pte Ltd 4 Leng Kee Road SIS Building 05 11A S...

Page 3: ...d in an updata ble ring binder format and do not apply to this manual PCB Information PCB information is provided for all current issue PCBs as well as all previous issue PCBs manufactured in production quanti ties and is grouped according to PCB Thus you will find the parts list grid reference index if necessary PCB layouts and circuit diagram s for each individual PCB grouped together Errors If ...

Page 4: ...ed stored or reduced to any electronic medium or machine readable form without prior written permission from Tait Electronics Ltd Ordering Tait Service Manuals Service Manuals should be ordered from your nearest Tait Branch or approved Dealer When ordering quote the Tait Internal Part Number IPN and where applicable the version Date Of Issue IPN M889 00 100 T889 Power Amplifier Service Manual Issu...

Page 5: ...vided into seven Sections as listed below There is a detailed table of contents at the start of each Section Section Title 1 General Information 2 Circuit Operation 3 Introduction To Servicing 4 Initial Tuning Adjustment 5 Fault Finding 6 Installation 7 PCB Information ...

Page 6: ...95 3 5 02 10 95 3 6 02 10 95 3 7 02 10 95 3 8 02 10 95 3 9 02 10 95 3 10 02 10 95 4 1 02 10 95 4 2 blank 4 3 02 10 95 4 4 02 10 95 5 1 02 10 95 5 2 blank 5 3 02 10 95 5 4 02 10 95 5 5 blank fold out 5 6 02 10 95 fold out 5 7 02 10 95 5 8 02 10 95 5 9 02 10 95 5 10 blank 6 1 02 10 95 6 2 blank 6 3 02 10 95 6 4 02 10 95 6 5 02 10 95 6 6 blank 7 1 1 02 10 95 7 1 2 blank 7 1 3 02 10 95 7 1 4 02 10 95 ...

Page 7: ...tion provides a brief description of the T889 PA along with detailed specifica tions and a list of variants available The following topics are covered in this section Section Title Page 1 1 Introduction 1 3 1 2 1 2 1 1 2 2 Specifications Introduction General 1 4 1 4 1 4 1 3 Versions 1 6 ...

Page 8: ...1 2 General Information M889 00 02 10 95 Copyright TEL ...

Page 9: ...mitter can still produce half its rated power VSWR and thermal protection is incorporated into the basic design while monitoring and alarm signals are available for both forward and reverse power The output power is adjustable from the front panel The main PCB is mounted directly on a die cast chassis heatsink For long term relia bility four high quality low loss Teflon PCBs are sweated to the mai...

Page 10: ... test methods and the conditions which apply for Type Approval testing in all countries can be obtained from Tait Electronics Ltd 1 2 2 General Power Output Rated Power 90W Range Of Adjustment 20 to 100W typical Duty Cycle Rating 90W continuous to 60 C Intermodulation 70dBc or 40dBi1 with 25dB isolation PA with output isolator interfering signal of 30dBc Mismatch Capability Ruggedness infinite VSW...

Page 11: ...10 95 Spurious Emissions Conducted Transmit 36dBm to 1GHz 30dBm to 4GHz Standby 57dBm to 1GHz 47dBm to 4GHz Radiated Transmit 36dBm to 1GHz 30dBm to 4GHz Standby 57dBm to 1GHz 47dBm to 4GHz Dimensions Height 191mm Width 120mm Length 340mm Weight 3 5kg ...

Page 12: ...1 6 General Information M889 00 02 10 95 Copyright TEL 1 3 Versions Description Version 10 800 870MHz ...

Page 13: ...ion Title Page 2 1 Introduction 2 3 2 2 RF Circuitry 2 3 2 3 2 3 1 2 3 2 2 3 3 2 3 4 2 3 5 2 3 6 Control Circuitry Power Control Driver Power Level Thermal Protection Forward And Reverse Power Alarms Forward And Reverse Power Metering Fan Control Circuitry 2 4 2 5 2 5 2 5 2 5 2 6 2 6 Figure Title Page 2 1 2 2 2 3 High Level Block Diagram Control Circuitry Block Diagram Fan Control Logic Diagram 2 ...

Page 14: ...2 2 Circuit Operation M889 00 02 10 95 Copyright TEL ...

Page 15: ...hich delivers a minimum of 40W This signal is split via three 3dB couplers L13 L14 L15 and used to drive the four final amplifiers Q3 Q4 Q5 Q6 These outputs are recom bined by L40 L41 L42 and passed to the antenna socket via the directional coupler and low pass filter The directional coupler senses forward and reflected power which is rectified D1 D2 and passed to the control circuitry for meterin...

Page 16: ...2 4 Circuit Operation M889 00 02 10 95 Copyright TEL 2 3 Control Circuitry Figure 2 2 Control Circuitry Block Diagram REF ...

Page 17: ...adjust will be 20 to 50W 2 3 3 Thermal Protection At excessively high temperatures the output power will automatically reduce to a pre set level set by RV74 thus preventing the PA from overheating A thermistor controlled voltage divider R68 R72 applies a voltage to a comparator with hysteresis IC1 pins 12 13 14 The output current from the comparator is summed into the power control network via RV7...

Page 18: ...eater than 10 C A logic AND function is applied to the comparator outputs by Q20 and Q21 thereby turning on the fan unconditionally via Q17 and Q18 if the heatsink temperature exceeds 70 C A logic OR function is applied to comparator IC3 pins 8 9 10 and Tx KEY signals thereby turning on the fan when the transmitter is keyed and the temperature is between 10 C and 70 C If the temperature drops belo...

Page 19: ... Head Screws UNC Thread Screws Screw Torques Disassembly Reassembly 3 5 3 5 3 5 3 5 3 5 3 3 3 3 1 3 3 1 1 3 3 1 2 3 3 2 Component Replacement Leaded Components Desoldering Iron Method Component Cutting Method Surface Mount Devices 3 6 3 6 3 6 3 6 3 7 3 4 3 4 1 3 4 1 1 3 4 1 2 3 4 2 To Replace PA Transistors Capacitor Transistor Spacing Q1 2SC2933 Pre Driver Q2 Q3 Q4 Q5 Q6 SD1414 Replacement Proced...

Page 20: ...3 2 Introduction To Servicing M889 00 02 10 95 Copyright TEL ...

Page 21: ...andling proce dures refer to the manufacturers data books e g Philips data books covering CMOS devices or Motorola CMOS data books Section 5 Handling etc Figure 3 1 Typical Anti static Bench Set up An anti static bench kit refer to Figure 3 1 is available from Tait Electronics Ltd under the usual consumable goods ordering system The kit is held in stock under IPN 937 00000 34 and contains 1 conduc...

Page 22: ...n current use all contain some beryllium oxide This sub stance while perfectly harmless in its normal solid form can become a severe health hazard when it has been reduced to dust For this reason the RF power transistors should not be broken open mutilated filed machined or physically damaged in any way that can produce dust particles ...

Page 23: ...ll black finish Pozidriv screws used in the T889 are 4 40 UNC thread and cannot be interchanged with M3 screws Note that different lengths are used in different applica tions 3 2 3 Screw Torques It is important to tighten the cover and power transistor securing screws to the correct torque to ensure that the T889 maintains its specified performance We recommend the following torque settings cover ...

Page 24: ...3 or 4 circles have been com pleted Remove the tip while continuing suction to ensure that all solder is removed from the joint then stop the suction Before pulling the lead out ensure it is not stuck to the plating If the lead is still not free resolder the joint and try again Note The desoldering iron does not usually have enough heat to desolder leads from the ground plane Additional heat may b...

Page 25: ...handling removal and replacement techniques This equipment should be serv iced only by an approved Tait Dealer or Service Centre equipped with the necessary facilities Repairs attempted with incorrect equipment or by untrained personnel may result in permanent damage If in doubt contact Tait Electronics Ltd or your nearest Tait Branch or Subsidiary ...

Page 26: ...ced in exactly the same position Note Be sure to measure between the transistor body and the tabs not the body of the capacitors Position the capacitors labelled b hard up against the transistor body 3 4 1 2 Q2 Q3 Q4 Q5 Q6 SD1414 Position all capacitors labelled b hard up against the transistor body 3 4 2 Replacement Procedure Desolder the tabs and grounding clips if an SD1414 by heating with a so...

Page 27: ...M889 00 Introduction To Servicing 3 9 Copyright TEL 02 10 95 Figure 3 2 Typical Transistor Capacitor Spacing Q1 Q2 Shown Grounding Clips b b b b b c c b measurement a Q1 Q2 ...

Page 28: ...the heatsink casting and desoldering it from the PCB Disconnect the input 50 ohm coaxial cable by unplugging it at the PCB Disconnect the battery positive and negative feed wires from the PCB Disconnect the alarm and metering wires from the PCB Lift the PCB gently from the heatsink to gain access to the underside of the PCB Caution Do not operate the PA with the PCB detached as the heatsink is use...

Page 29: ...arm adjust ment and power meter calibration The following topics are covered in this section Section Title Page 4 1 Initial Connections 4 3 4 2 RF Alignment 4 3 4 3 High Temperature Shutdown Power Level 4 3 4 4 Low Forward Power Alarm 4 3 4 5 High Reverse Power Alarm 4 4 4 6 Remote Forward Power Meter Calibration 4 4 4 7 Remote Reverse Power Meter Calibration 4 4 ...

Page 30: ...4 2 Initial Tuning Adjustment M889 00 02 10 95 Copyright TEL ...

Page 31: ...n the drive source the power output should exceed 100W Adjust RV69 driver power level until the output power drops to 100W Adjust RV63 to reduce the power output to the required level e g 90W 4 3 High Temperature Shutdown Power Level Set RV63 power control to the required output power Earth pin 12 of IC1 the pad at NTC R72 is convenient Adjust RV74 shutdown power level for an output power of 20W R...

Page 32: ...ing an unterminated 150W 3dB pad to the PA output This will result in a return loss of 6dB Note Remote indication is available at D range pin 4 4 6 Remote Forward Power Meter Calibration If a remote meter is connected adjust RV43 forward power meter for the remote reading to agree with the RF power meter reading 4 7 Remote Reverse Power Meter Calibration If a remote meter is connected connect a 50...

Page 33: ...r contact your nearest authorised Tait Dealer or Service Centre Further assistance may be obtained from the Customer Support Group Radio Infrastructure Division Tait Elec tronics Ltd Christchurch New Zealand The following topics are covered in this section Section Title Page 5 1 Visual Checks 5 3 5 2 Component Checks 5 3 5 3 DC Checks 5 3 5 4 RF Checks 5 4 5 5 5 5 1 5 5 2 5 5 3 Fault Finding Chart...

Page 34: ...5 2 Fault Finding M889 00 02 10 95 Copyright TEL ...

Page 35: ...ium or low resistance ranges The collector current drawn by multi junction transistors is a further guide to their per formance If an IC is suspect the most reliable check is to measure the DC operating voltages Due to the catastrophic nature of most IC failures the pin voltages will usually be markedly different from the recommended values in the presence of a fault The recommended values can be ...

Page 36: ... transistors Q1 Q6 Note 1 Always test individual PA stages at the 50Ω test points located at the ends of the semi rigid transmission lines furthest away from the RF transistors Note 2 Always test Q1 and Q2 as a pair Note 3 Use 50Ω semi rigid coax for the flying test leads For problems with the power control circuitry refer to the Power Control Fault Finding Chart Section 5 5 2 Transistor Input Tra...

Page 37: ...M889 00 Fault Finding 5 5 Copyright TEL 02 10 95 replace A4 pages 5 5 5 6 with A3 pages 5 5 5 6 file name 88900_5a 100 ...

Page 38: ...5 6 Fault Finding M889 00 02 10 95 Copyright TEL replace A4 pages 5 5 5 6 with A3 pages 5 5 5 6 file name 88900_5a 100 ...

Page 39: ...rid Check components in LPF Check output N type connector for short or wear Replace parts as necessary N N N Y Y Y Y N N Y Y N Y N N Y Y Is Q2 output 40W see Figure 5 1 A B N Check the condition of splitter hybrids L13 L14 L15 Are there any shorts between the splitter wires or broken wires Q3 Q4 Q5 Q6 outputs each 30W test each individually as per Figure 5 1 C D Check the condition of combiner hyb...

Page 40: ...e adjusting RV74 until PA output power is set to 35W Does high reverse power alarm LED light when PA operated into a mismatch of 3 1 or worse To test connect an unterminated 3dB pad to the PA output thereby setting up a 3 1 mismatch High Reverse Power Alarm Check Does the output power reduce to 35W at high operating temperatures To test heat R72 with the tip of a soldering iron Over Temperature Sh...

Page 41: ...stop the fan Spray freeze on R116 OR short R113 Check IC3 pin 14 11V Check Q21 Q20 N N Y Y Check Q20 Q21 collector voltages Check Q17 Q18 Check IC3 pin 14 1V Check Q19 Check Tx key is low at ground Do not key transmitter Does high temperature control circuit activate fan Heat R72 with tip of soldering iron Check IC3 pin 8 11V Check Q21 Q20 Fan control OK Heat R72 to 70 C with tip of soldering iron...

Page 42: ...5 10 Fault Finding M889 00 02 10 95 Copyright TEL ...

Page 43: ...M889 00 Fault Finding 5 5 Copyright TEL 02 10 95 ...

Page 44: ... its pad 2 Solder the test lead outer core to the earth plane remove the resist first 3 Solder the inner cores of L1 and the test lead together off the PCB main PCB L1 input test lead 50Ω test point Output Test Lead Q3 Q6 Q4 Shown Refer to drawing B above 1 Desolder the appropriate DC blocking capacitor and resolder on edge 2 Remove the wireline clamping plate and solder the test lead outer core t...

Page 45: ...tion of the basic rack mounting and wiring procedures The following topics are covered in this section Section Title Page 6 1 Rack Mounting 6 3 6 2 Rack Wiring 6 5 6 3 Power Supply 6 5 Figure Title Page 6 1 Guide Rails 6 3 6 2 Chassis Connectors 6 3 6 3 Latched Position 6 4 6 4 D Range Wiring Rear View 6 5 ...

Page 46: ...6 2 Installation M889 00 02 10 95 Copyright TEL ...

Page 47: ... guide rail is located with just one screw The PA is secured into the guide with two front panel mounting screws The RF input via the rear panel BNC connector should be connected to an adjacent T881 transmitter The RF output is via the rear N type connector whilst all DC audio and control connections are via the D range connector The guide rails will allow the PA to be latched in the extended posi...

Page 48: ...6 4 Installation M889 00 02 10 95 Copyright TEL Figure 6 3 Latched Position Stop RF Output Top Rail RF Input D Range Bottom Rail ...

Page 49: ...f access to the rear of the rack frame is restricted the cables should be long enough to permit full withdrawal of the chassis from the guide Figure 6 4 D Range Wiring Rear View 6 3 Power Supply If a power supply other than an appropriate Tait model is used ensure that it is capable of providing enough current to drive the T800 system and is also free from excessive ripple or noise Reverse Power M...

Page 50: ...6 6 Installation M889 00 02 10 95 Copyright TEL ...

Page 51: ... 7 PCB Information This section provides parts lists a grid reference index PCB layouts and circuit diagrams for the T889 PA This section contains the following information Section Title IPN Page 7 1 Introduction 7 1 3 7 2 T889 PA PCB 220 01326 01 7 2 1 ...

Page 52: ...7 1 2 PCB Information M889 00 02 10 95 Copyright TEL ...

Page 53: ...nd description A number in the variant column indicates that this component is fitted only to that variant The miscellaneous and mechanical section lists the variant and common parts in IPN order Grid Reference Index To assist in locating components and labelled pads on the PCB layouts and circuit diagrams a com ponent grid reference index has been provided This index lists the components and pads...

Page 54: ...o the sheet number printed on the bottom right hand corner of the CAD diagram and the last two characters refer to the location on that sheet of the continuation of the circuit e g 1 D4 If more than one line is represented indicated by a double thickness line a dot with a reference label will follow the route each individual line represents ...

Page 55: ...tion contains the following information IPN Section Page 220 01326 01 Parts List Mechanical Miscellaneous Parts Grid Reference Index PCB Layout Bottom Side PCB Layout Top Side RF Section Circuit Diagram Control Section Circuit Diagram 7 2 2 7 2 5 7 2 7 7 2 9 7 2 10 7 2 11 7 2 12 ...

Page 56: ...ER 0805 CHIP 4N7 10 X7R 50V C53 029 01270 02 CAP MICA 5MM CASE 2P7 0 25P C54 029 01560 01 CAP MICA 10MM CASE 5P6 0 25P C55 029 01680 01 CAP MICA 10MM CASE 6P8 5 C56 029 01560 01 CAP MICA 10MM CASE 5P6 0 25P C57 029 01270 02 CAP MICA 5MM CASE 2P7 0 25P C58 015 06100 08 CAP CER 1206 CHIP 100N 10 X7R 50V C59 014 07470 03 L CAP TANT CHIP 4U7 25V 20 6X3 2X2 5M C60 015 24470 08 CAP CER 0805 CHIP 4N7 10 ...

Page 57: ...10008 48 S XSTR SMD BCW60 BC848B215 NPN SOT23 AF see note below Note Fit two new grounding clips IPN 319 40009 00 when replacing SD1414 transistors see Section 3 4 2 R1 036 02100 03 L RES 1218 PWR CHIP 10E 20 1W R2 036 02100 03 L RES 1218 PWR CHIP 10E 20 1W R3 036 02100 02 RES 10E 1206 CHIP 200V 250MW RC01 R4 036 02100 03 L RES 1218 PWR CHIP 10E 20 1W R5 036 02100 03 L RES 1218 PWR CHIP 10E 20 1W ...

Page 58: ... 5 R120 036 14680 00 RES M F 0805 CHIP 6K8 5 R121 036 14100 00 RES M F 0805 CHIP 1K 5 R122 036 14100 00 RES M F 0805 CHIP 1K 5 R123 036 13470 00 RES M F 0805 CHIP 470E 5 R124 036 13220 00 RES M F 0805 CHIP 220E 5 R125 036 16100 00 RES M F 0805 CHIP 100K 5 R126 036 16150 00 RES M F 0805 CHIP 150K 5 R127 036 15100 00 RES M F 0805 CHIP 10K 5 R128 036 16100 00 RES M F 0805 CHIP 100K 5 R129 036 15220 0...

Page 59: ...11182 01 HEATSINK T889 COMPLETE D CAST MECH DRILLED 303 23117 00 COVER COMPL A2M2223 2 A2M2223 1 SIDE 303 50005 00 CONTACT A4M2311 SPRING EARTH T858 306 01010 00 FERRULE A4M948 HANDLE FXD EQUIP 308 01007 00 HANDLE A4M949 FXD EQUIP 316 06515 00 PNL FRT T889 SCRND COMPLETE 318 01011 00 RAIL A2M1872 BOTTOM T377 PA 318 01012 00 RAIL A3M1873 TOP T377 PA 319 01152 00 SHIELD A3M2250 F THRU MTG T857 ASSEM...

Page 60: ...7 2 6 PCB Information M889 00 02 10 95 Copyright TEL ...

Page 61: ... P0 C95 1 T7 2 P0 C96 1 V5 2 K0 C97 1 M9 1 U9 C98 1 N9 1 V9 C99 1 V6 2 L0 C102 1 U8 2 Q2 C103 1 T8 2 Q2 C104 1 U7 2 Q3 C105 1 T8 2 R3 C106 1 T8 2 R2 C107 1 U9 2 Q1 C108 1 U3 2 J8 C109 1 U4 2 H4 C114 1 V10 2 A8 C115 1 V9 2 A4 C116 1 U5 2 R7 C117 1 W7 2 P9 C118 1 W7 2 P8 C119 1 W8 2 P7 C120 1 W8 2 P6 C121 1 V3 2 P5 C122 1 V3 2 P4 C123 1 U5 2 Q7 C124 1 U5 2 Q7 C125 1 U5 2 R8 C126 1 U3 2 N6 C127 1 U3 ...

Page 62: ...0A 1 R4 1 B3 R61 1 V8 2 C0 R62 1 V8 2 C0 RV63 1 U6 2 M3 RV63A 1 V7 2 M2 R64 1 U8 2 N3 R65 1 U7 2 P1 R66 1 U9 2 P2 R67 1 V6 2 K1 R68 1 V6 2 K2 RV69 1 V2 2 E0 R69 1 U6 2 F0 R70 1 U7 2 F0 R72 1 M9 1 T9 R73 1 V5 2 L0 RV74 1 V2 2 M1 R75 1 V6 2 M0 R76 1 V6 2 M0 R77 1 U8 2 Q3 R78 1 U8 2 Q2 R79 1 U7 2 N1 R80 1 T8 2 R3 R81 1 U6 2 D7 R82 1 U6 2 D8 R83 1 V9 2 C4 R84 1 V6 2 C4 R85 1 S2 2 E3 R86 1 U4 2 G7 R87 ...

Page 63: ...M889 00 PCB Information 7 2 9 Copyright TEL 02 10 95 T889 PCB Layout Bottom Side 220 01326 01 ...

Page 64: ...7 2 10 PCB Information M889 00 02 10 95 Copyright TEL T889 PCB Layout Top Side 220 01326 01 L46 C97 C98 L19 L29 L96 C59 L22 L16 L32 L26 L1 L49 L43 L12 L39 L33 C45 C38 C15 C32 C25 ...

Page 65: ...M889 00 PCB Information 7 2 11 Copyright TEL 02 10 95 T889 RF Section 220 01326 01 ...

Page 66: ...7 2 12 PCB Information M889 00 02 10 95 Copyright TEL T889 Control Section 220 01326 01 ...

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