M889-00 T889 Power Amplifier UHF FM 800-870MHz Issue 100 October 1995 M889-00-100 Copyright TEL 02/10/95
M889-00 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 Head Office New Zealand Tait Electronics Ltd 558 Wairakei Road P.O. Box 1645 Christchurch New Zealand Phone: 64 3 358-3399 Fax: 64 3 358-3636 Australia Tait Electronics (Aust) Pty Ltd 275 Toombul Road Northgate 4013 P.O.
M889-00 About This Manual Scope This manual contains general, technical and servicing information on the T889 Power Amplifier. Revision Control Each page in this manual has a date of issue. This is to comply with various Quality Standards, but will also serve to identify which pages have been updated and when. Each page and its publication date is listed in the “List of Effective Pages”.
M889-00 Copyright All information contained in this manual is the property of Tait Electronics Ltd. All rights are reserved. This manual may not, in whole or 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. Ordering Tait Service Manuals Service Manuals should be ordered from your nearest Tait Branch or approved Dealer.
M889-00 Table Of Contents This manual is divided into seven Sections as listed below. There is a detailed table of contents at the start of each Section.
M889-00 List Of Effective Pages The total number of pages in this Manual is 64, as listed below. Page Issue Date Page Issue Date 1 2 3 4 5 6 02/10/95 02/10/95 02/10/95 02/10/95 02/10/95 02/10/95 5.10 blank 1.1 1.2 1.3 1.4 1.5 1.6 02/10/95 blank 02/10/95 02/10/95 02/10/95 02/10/95 6.1 6.2 6.3 6.4 6.5 6.6 02/10/95 blank 02/10/95 02/10/95 02/10/95 blank 7.1.1 7.1.2 7.1.3 7.1.4 02/10/95 blank 02/10/95 02/10/95 2.1 2.2 2.3 2.4 2.5 2.6 02/10/95 blank 02/10/95 02/10/95 02/10/95 02/10/95 3.1 3.
General Information M889-00 1 1.1 General Information This section provides a brief description of the T889 PA, along with detailed specifications and a list of variants available. The following topics are covered in this section. Section Title Page 1.1 Introduction 1.3 1.2 Specifications 1.4 1.2.1 Introduction 1.4 1.2.2 General 1.4 Versions 1.6 1.
1.
General Information M889-00 1.1 1.3 Introduction The T889 is an FM base station power amplifier designed for single or multichannel operation within the frequency range 800 to 870MHz. The output power capability is 20 to 100W. The PA comprises a broad band, two stage drive amplifier whose output is split to drive four separate output stages. The outputs from these final stages are then recombined and filtered before being fed to the output socket.
1.4 General Information 1.2 Specifications 1.2.1 Introduction M889-00 The performance figures given are minimum figures, unless otherwise indicated, for equipment tuned with the maximum switching band and operating at standard room temperature (+22°C to +28°C). Where applicable, the test methods used to obtain the following performance figures are those described in the EIA specification. However, there are several parameters for which performance according to the CEPT specification is given.
General Information M889-00 1.5 Spurious Emissions: Conducted - Transmit - Standby Radiated - Transmit - Standby .. -36dBm to 1GHz -30dBm to 4GHz .. -57dBm to 1GHz -47dBm to 4GHz .. -36dBm to 1GHz -30dBm to 4GHz .. -57dBm to 1GHz -47dBm to 4GHz Dimensions: Height Width Length Weight: Copyright TEL .. 191mm .. 120mm .. 340mm .. 3.
1.6 General Information 1.
Circuit Operation M889-00 2 2.1 Circuit Operation This section provides a basic description of the circuit operation of the T889 PA. The following topics are covered in this section. Section Title Page 2.1 Introduction 2.3 2.2 RF Circuitry 2.3 2.3 Control Circuitry 2.4 2.3.1 Power Control 2.5 2.3.2 Driver Power Level 2.5 2.3.3 Thermal Protection 2.5 2.3.4 Forward And Reverse Power Alarms 2.5 2.3.5 Forward And Reverse Power Metering 2.6 2.3.6 Fan Control Circuitry 2.
2.
Circuit Operation M889-00 2.1 2.3 Introduction 30W Q3 Power Control 60W Vsupply L13 Q16 L40 Q4 4W 40W 30W L14 L41 100W 120W LPF RF In Pad Q1 30W Q2 RF Out Directional Coupler Q5 L15 L42 60W Q6 30W Figure 2.1 High Level Block Diagram The T889 comprises a three stage RF power amplifier with extensive control circuitry. The final stage is composed of four transistors (Q3, Q4, Q5 & Q6) whose outputs are combined to provide the rated output power.
2.4 Circuit Operation 2.3 Control Circuitry M889-00 REF Figure 2.
Circuit Operation M889-00 2.3.1 2.5 Power Control The DC voltages from the directional coupler representing forward and reflected power are buffered by the two voltage followers, IC3 pins 1, 2 & 3 and pins 5, 6 & 7. Their outputs are summed at an integrator (IC1 pins 8, 9 & 10), which drives the series pass control element (Q16). Forward and reflected power are summed so that, under high output VSWR, the power control turns the PA down.
2.6 Circuit Operation 2.3.5 Forward And Reverse Power Metering M889-00 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 Invert 13.8V Filtered Tx Key Q19 OR NAND Q17 Q18 Comparator NTC Ref High Temp. Sense + R72 IC3C NTC Comparator Low Temp.
Introduction To Servicing M889-00 3 3.1 Introduction To Servicing This section provides some general and advisory information on servicing procedures. The following topics are covered in this section. Section 3.1 Title Page General 3.3 3.1.1 Caution: CMOS Devices 3.3 3.1.2 Caution: Aerial Load 3.3 3.1.3 Caution: Beryllium Oxide & Power Transistors 3.4 Mechanical 3.5 3.2.1 Pozidriv Recess Head Screws 3.5 3.2.2 UNC Thread Screws 3.5 3.2.3 Screw Torques 3.5 3.2.
3.
Introduction To Servicing M889-00 3.1 3.3 General If you require further information about the T889 or this manual, contact your nearest authorised Tait Dealer or Service Centre. Further assistance may be obtained from the Customer Support Group, Radio Infrastructure Division, Tait Electronics Ltd, Christchurch, New Zealand. When requesting this information, please quote the equipment type number (e.g. T889-10) and serial number.
3.4 Introduction To Servicing 3.1.3 Caution: Beryllium Oxide & Power Transistors M889-00 The RF power transistors in current use all contain some beryllium oxide. This substance, 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.
Introduction To Servicing M889-00 3.2 Mechanical 3.2.1 Pozidriv Recess Head Screws 3.5 Pozidriv recess head screws are the preferred standard on all Tait manufactured equipment. The very real advantages of this type of screw will not be realised unless the correct screwdrivers are used by servicing personnel. 3.2.2 UNC Thread Screws All black finish Pozidriv screws used in the T889 are 4-40 UNC thread and cannot be interchanged with M3 screws.
3.6 Introduction To Servicing 3.3 Component Replacement 3.3.1 Leaded Components M889-00 Whenever components are removed from or fitted to the PCB, care must be taken to avoid damage to the track. The two satisfactory methods of removing components from PTH PCBs are detailed below. Note: The first method requires the use of a desoldering station, e.g. Philips SBC 314 or Pace MBT-100E. 3.3.1.
Introduction To Servicing M889-00 3.3.2 Caution: Copyright TEL 3.7 Surface Mount Devices Surface mount devices (SMD's) require special storage, handling, removal and replacement techniques. This equipment should be serviced 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.
3.8 Introduction To Servicing 3.4 To Replace PA Transistors M889-00 Caution: As the location of certain components in the PA is critical to performance, it is important that any components removed or disturbed are refitted in EXACTLY the same position. Caution: Do not solder the tabs before torquing down otherwise the device may be broken. 3.4.1 Capacitor /Transistor Spacing Refer to Figure 3.2. 3.4.1.
Introduction To Servicing M889-00 3.9 Grounding Clips b b Q2 b b measurement a c c Q1 b b Figure 3.
3.10 Introduction To Servicing 3.5 To Remove The PCB From The Heatsink M889-00 Most components are soldered topside only, but in some cases access to the underside of the PCB is necessary. Remove the D-range connector. Disconnect the power feed to the fan. Remove the 13 PCB retaining screws (2 are hidden beneath the harmonic filter shield). Remove the transistor mounting screws. Remove the mounting screws for the TO-220 devices: R6, R7, R9, R16, R17, R17a and R18.
Initial Tuning & Adjustment M889-00 4 4.1 Initial Tuning & Adjustment The following section describes the initial set-up procedures, including alarm adjustment 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.
4.
Initial Tuning & Adjustment M889-00 4.1 4.3 Initial Connections Connect the PA to a power supply, an output RF load and a power meter as detailed below: power supply rating RF load >30A >150W. Provide a keyed RF drive at the required frequency. Connect the drive source key line to pin 12 of the external connector. Set RV69 (temperature shutdown) fully anticlockwise to avoid RF power cycling between the levels as set by RV63 and RV74. 4.2 RF Alignment Set RV63 (power control) fully clockwise.
4.4 Initial Tuning & Adjustment 4.5 High Reverse Power Alarm M889-00 Set RV63 to the required output power. Connect a known mismatch of the required value to the PA output. Apply RF drive and Tx key. Adjust RV52 (reverse power alarm) so that the front panel high reverse power LED just lights. Example: A VSWR of 3:1 can be simulated by connecting 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.
Fault Finding M889-00 5 5.1 Fault Finding The following test procedures and fault finding flow charts may be used to help locate a hardware problem, however they are by no means a complete fault finding procedure. If the fault still exists after having progressed through them in a logical manner, contact your nearest authorised Tait Dealer or Service Centre.
5.
Fault Finding M889-00 5.1 5.3 Visual Checks Remove the cover from the T889 and inspect the PCB for damaged or broken components, paying particular attention to the surface mounted devices (SMD's). Check for defective solder joints. If repair or replacement is considered necessary, refer to Sections 3.3, 3.4, 3.5 and 3.6. 5.
5.4 Fault Finding 5.4 RF Checks M889-00 The PA Fault Finding Chart (Section 5.5.1) provides a systematic approach for locating a fault in the RF circuitry. Use this chart in conjunction with Figure 5.1, which shows the locations of the 50Ω input and output test points for RF transistors Q1-Q6.
M889-00 Fault Finding 5.5 replace A4 pages 5.5/5.6 with A3 pages 5.5/5.6, file name 88900_5a.
5.6 Fault Finding M889-00 replace A4 pages 5.5/5.6 with A3 pages 5.5/5.6, file name 88900_5a.
Fault Finding M889-00 5.5 Fault Finding Charts 5.5.1 PA RF circuitry OK. Y 5.7 Is maximum power >90W @ 800-870MHz? N Are RV69 & RV63 fully clockwise? Rotate clockwise: RV63 first, RV69 second. N Y Is the drive from the exciter 4W? N Set drive to 4W. Y Is Q2 output >40W? (see Figure 5.1, A & B) Check Q1 collector >13V. Check Q2 collector 5-14V. Check for shorts around transistor caps C2, 3, 9, 19, 10, 11, 12, 13 & 14. Check transistor junction resistance (see Section 5.2).
5.8 Fault Finding 5.5.2 Power Control M889-00 RF Power Level Control Check Ensure RV69 is fully clockwise. Check sense voltages from directional coupler on IC3 pins 1 & 7. N Does output power adjust over the range 20-100W using RV63? Y Low Forward Power Alarm Check Does low forward power alarm LED light when output power reduced to 60W using RV63? Use RV63 to adjust output power to 60W. Adjust RV48 until forward power LED is just lit.
Fault Finding M889-00 5.5.3 5.9 Fan Control Circuitry Key transmitter. Does fan run at room temperature? Check Q20 & Q21 collector voltages. Check Q17 & Q18. Check IC3 pin 14 <1V. Check Q19. Check Tx-key is low (at ground). N Y Spray "freeze" on R116 or short R113. Does the low temperature inhibit circuit stop the fan? N Spray "freeze" on R116 OR short R113. Check IC3 pin 14 >11V. Check Q21 & Q20. Y Do not key transmitter. Heat R72 to >70°C with tip of soldering iron.
5.
M889-00 Copyright TEL Fault Finding 5.
Fault Finding 5.6 M889-00 B Output Test Lead - Q1 & Q2 1. Desolder C15 and resolder on edge L46 as shown. 2. Remove the wireline clamping plate and solder the test lead outer core to the outer core of the wireline (L14 shown). 3. Solder the inner core of the test lead to the raised end of C15. C97 output test lead (to wattmeter, analyser etc.) L49 50Ω test point C98 C15 (DC blocking capacitor) L12 (transmission line) L14 (wireline) L12 L43 C15 C45 C38 C59 Teflon PCB main PCB 4.
Installation M889-00 6 6.1 Installation The following section gives a brief description 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.
6.
Installation M889-00 6.1 6.3 Rack Mounting The T889 PA is designed for use in a standard 483mm rack frame using the supporting guide rails supplied with the unit (refer to Figure 6.1). The lower guide rail is located in the rack frame with three screws, two at the rear and one at the front. The short upper guide rail is located with just one screw. The PA is secured into the guide with two front panel mounting screws.
6.4 Installation Stop M889-00 Top Rail RF Output RF Input D-Range Bottom Rail Figure 6.
Installation M889-00 6.2 6.5 Rack Wiring Wire the D-range connector as shown in Figure 6.4. Ensure that the cables are not subjected to any stresses due to tight bends or incorrect lengths. The RF coaxial cables to the BNC and N-type connectors should be free from acute bends or twists. If 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. Pin 9 Pin 1 +13.
6.
PCB Information M889-00 7 7.1.1 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 7.1 Introduction 7.2 T889 PA PCB Copyright TEL IPN Page 7.1.3 220-01326-01 7.2.
7.1.
PCB Information M889-00 7.1 7.1.3 Introduction PCB Identification All PCBs are identified by a unique 10 digit number, the last 2 digits of which define the issue status. The issue status starts at 00 and increments through 01, 02, 03, etc. as the PCB is updated. Some issue PCBs never reach full production status and are therefore not included in this manual. A letter following the 10 digit IPN has no relevance in identifying the PCB for service purposes.
7.1.4 PCB Information M889-00 the line to indicate where the rest of the circuitry is located. The first digit refers to 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.
PCB Information M889-00 7.2 7.2.1 T889 PA PCB This section contains the following information. IPN 220-01326-01 Copyright TEL Section Page Parts List 7.2.2 Mechanical & Miscellaneous Parts 7.2.5 Grid Reference Index 7.2.7 PCB Layout - Bottom Side 7.2.9 PCB Layout - Top Side 7.2.10 RF Section Circuit Diagram 7.2.11 Control Section Circuit Diagram 7.2.
7.2.2 PCB Information M889-00 T889 Parts List (IPN 220-01326-01) How To Use This Parts List The components listed in this parts list are divided into two main types: those with a circuit reference (e.g. C2, D1, R121, etc) and those without (miscellaneous and mechanical). Those with a circuit reference are grouped by component type in numerical order. Each component entry comprises three or four columns: the circuit reference, variant number (if applicable), IPN and description.
PCB Information M889-00 Ref IPN Description Ref D3 D4 D6 D13 001-00011-60 001-10000-70 001-10000-70 001-10000-70 (S) DIODE SR2607 6A/30V (S) DIODE SMD BAV70 DUAL SWITCH SOT-23 CO (S) DIODE SMD BAV70 DUAL SWITCH SOT-23 CO (S) DIODE SMD BAV70 DUAL SWITCH SOT-23 CO FTC 012-04100-05 CAP F/THRU 1N SUPPR FLTR STUD MTG (fan circuit; mounted on heatsink) IC1 IC2 IC3 IC4 IC5 002-10003-24 002-00014-62 002-10003-24 002-00014-62 002-10003-58 (S) IC SMD 324 QUAD OP AMP SO14 (S) IC 317L 100MA REG 3 TERMINAL
7.2.
PCB Information M889-00 7.2.5 T889 Mechanical & Miscellaneous Parts (220-01326-01) IPN Description IPN Description 012-04150-01 CAP CER F/THRU 1N5 NO LEAD C1-C15 318-01011-00 RAIL A2M1872 BOTTOM T377 PA 318-01012-00 RAIL A3M1873 TOP T377 PA 051-00006-02 SOLDER SPRING 1.3MM A4M1877 (x6) (LED wire joints) 319-01152-00 SHIELD A3M2250 F/THRU MTG T857 ASSEMBLE D.RANGE BEAD FERRITE 7D 1.9*0.9*3.8MM STACK POLE ASSEMBLE D.
7.2.
PCB Information M889-00 7.2.7 T889 Grid Reference Index (IPN 220-01326-01) How To Use This Grid Reference Index The first digit in the PCB layout reference is a "1" or "2", indicating the top or bottom side layout respectively, and the last two characters give the location of the component on that diagram. The first digit in the circuit diagram reference is the sheet number, and the last two characters give the location of the component on that sheet.
7.2.
M889-00 PCB Information 7.2.
PCB Information 7.2.
M889-00 PCB Information 7.2.
7.2.
