Glenayre GL-T8541 User Manual Download

Page: 33 / 90

Glenayre Document Number: 9110.01002

GL-T8541 PA

09/10/99

THEORY OF OPERATION

t8541

p6.

fdk

Page: 6-7

Figure 6-4 The 3 to 1 Combiner Board Block Diagram

Reflected
Sample to
Metering

Forward
Sample to
Metering
Board

Board

Simplified Temperature Sensing Circuit

Temperature
Sample Output
to Metering Board

R5
Temperature
Sensor

+5V

R143

U4-A

R1
50

Ω

3-Way
Wilkinson Hybrid

C2
C3

C4
C5

C6
C7

CR1

CR2

Low Pass Filter

Directional
Coupler

3 to 1 UHF Combiner

RF Output to
Isolator or
Lightning
Arrester

RF Input
From PA
Board

Summary of Contents for GL-T8541

Page 1: ...Glenayre All rights reserved No part of this work may be reproduced or copied in any form or by any means graphic electronic or mechanical including photocopying recording taping or information retri...

Page 3: ...iption 3 1 3 2 1 Electrical Connectors 3 1 3 2 2 Chassis Cooling 3 1 3 2 3 PA Front 3 2 3 2 4 PA Rear 3 2 3 3 Conceptual Description 3 2 3 4 PA Module Interconnection 3 5 3 4 1 PA Module Dc Signal and...

Page 4: ...6 5 3 Directional Coupler 6 6 6 6 PA Module Overall RF Flow 6 8 6 7 Metering Board 6 9 6 7 1 Temperature Monitoring Circuit 6 9 6 7 2 Metering Board to Combiner Board to Amplifier Board Interface6 10...

Page 5: ...2 7 10 Troubleshooting 7 12 7 10 1 Troubleshooting Chart 7 12 7 11 Advanced Troubleshooting 7 15 7 11 1 Checking PA Module Supply Voltage 7 15 7 11 1 1 Open Transistor or Blown Fuse 7 15 7 11 1 2 Meas...

Page 6: ...e Document Number 9110 01002 Table of Contents 09 10 99 Page iv Copyright 1997 Glenayre 8 7 Combiner Board 8 5 8 7 1 Removal 8 5 8 7 2 Reinstallation 8 5 8 8 Metering Board 8 6 8 8 1 Removal 8 6 8 8 2...

Page 7: ...ematic page 1 or 2 2000 00601 6 18 Figure 6 11 Metering Board Schematic page 2 of 2 2000 00601 6 19 Figure 6 12 Driver Board Assembly Top View 2000 00050 6 20 Figure 6 13 Driver Board Schematic 2000 0...

Page 8: ...istor Gate and Drain Pads 7 22 Figure 8 1 Fan Panel Assembly exploded 8 7 Figure 8 2 Top Cover Details 8 8 Figure 8 3 Driver Board Mounting Diagram 8 9 Figure 8 4 3 to 1 Splitter Board Mounting Diagra...

Page 9: ...3 2 Metering Board J1 to Combiner Board J8 Connector Pinout 3 5 Table 6 1 GL T8541 PA Optional Isolator RF Power Output 6 2 Table 6 2 Metering Board to Combiner Board Interface 6 10 Table 6 3 Power A...

Page 11: ...cument Part Number Description GL T 8xx1 series transmitter system TM 9110 01004 Transmitter manual main binder with typical rackup of typical equipment Switching power supply manual 9130 00001 Glenay...

Page 12: ...cations Failures caused by unau thorized modifications force majeure lightning physical environmental or electrical damage including use with incompatible equipment are specifically excluded from this...

Page 13: ...itter system 2 2 GL T8541 PA Specifications Refer to Table 2 1 PA Specifications for power amplifier specifications Note the specifications are subject to change without notice Table 2 1 PA Specificat...

Page 14: ...gle isolator 40 dBc With dual isolator 70 dBc Operating voltage Vdc 26 5 28 Power consumption max At rated RF output 600 W Ambient temperature degrees C See derating factor 30 to 60 Humidity percent N...

Page 15: ...protection modular construction status output to exciter 3 2 Physical Description Refer to Figure 3 2 for board locations in the GL T8541 PA Refer to Table 3 1 for pc as semblies and part numbers 3 2...

Page 16: ...odulated RF is sent from the exciter to the PA input for amplification A control voltage from the exciter is used in the metering board to generate an AGC automatic gain control signal The AGC voltage...

Page 18: ...r Amplifier UHF 3 to 1 Combiner Board Low Pass Filter and Directional Coupler Part of Combiner Board UHF Driver Board UHF 3 to 1 Splitter 120 Watt UHF PA Board 120 Watt UHF PA Board 120 Watt UHF PA Bo...

Page 19: ...jumper straps Figure 3 3 shows the locations of the copper jumper straps in the PA module and the names of the signals they carry 3 4 1 1 The Metering Board Location The metering board is mounted on...

Page 20: ...output connector The sample is rectified and filtered providing a dc voltage proportional to the reflected power UHF 3 to 1 Combiner Board Low Pass Filter and Directional Coupler Part of Combiner Boa...

Page 21: ...y lifting 4 1 2 Test Equipment and Tools Required Common hand tools are required for disassembly and reassembly An RFI immune voltmeter may be required for voltage measurement An in line current meter...

Page 22: ...n 4 1 5 Power Requirement The power amplifier requires a 28 volt dc supply to operate as specified Total supply current varies depending on transmitter model other racked equipment and RF output One G...

Page 25: ...PA On and Off Control The PA does not contain an on off switch but turns on and off whenever the power supply equipment is turned on and off When the PA is on it remains in a standby condition until...

Page 27: ...iver board The 19 watt driver board signal is applied to the 1 to 3 splitter board which yields 6 watts from each of its three outputs Each of the three power amplifier boards supplies 100 watts to th...

Page 28: ...in the isolator reject load This increases the isolator and reject load dissipation and oper ating temperature 2 High antenna system VSWR means less power will be radiated from the antenna resulting...

Page 29: ...metering board When unkeyed the preamp key signal value is 0Vdc When keyed the preamp key signal has a value of 5 0Vdc The Q2 bias adjustment is R16 Depending on the bias setting the driver will put...

Page 30: ...errite beads are positioned around the coaxial to insure a balanced output signal with equal amplitudes from the center conductor and shield of the line Microstrip techniques augmented with chip capac...

Page 31: ...e transmitter with no RF input applied exciter RF output cable disconnected Refer to the VDT manual for addi tional information regarding the exciter VDT display The correct idle current adjustment un...

Page 32: ...ng amplifiers will be higher than normal while the defective amplifier current will be lower than normal or zero R1 on the combiner board is a balanced 3 resistor array arranged in a star formation Ea...

Page 33: ...g Forward Sample to Metering Board Board Simplified Temperature Sensing Circuit Temperature Sample Output to Metering Board R5 Temperature Sensor 5V R143 U4 A R1 50 3 Way Wilkinson Hybrid L2 L1 L3 L4...

Page 34: ...nayre 6 6 PA Module Overall RF Flow The overall RF flow through all of the boards in the PA module is shown in Figure 6 5 The discrete capacitors and inductors that connect the various traces of the R...

Page 35: ...ng board receives the following three monitoring signals from the PA module they are the heat sink temperature signal the forward power sample voltage the reflected power sample voltage The metering b...

Page 36: ...combiner board Refer to Table 6 2 for a listing of the metering board to combiner board interface connections Table 6 2 Metering Board to Combiner Board Interface J1 J8 Pin Number Function of the Conn...

Page 37: ...t dc fan power is fused at the front of the power supply 6 7 4 Metering Board Fuses Primary 28 volt dc operating power is received at terminal P1 on the metering board The negative side of the 28 volt...

Page 38: ...le 6 4 Metering Board Test Points Test Point and Color Voltage Regulator Function metering board unless specified otherwise TP1 black Ground None Ground reference point for test point measurement TP2...

Page 39: ...nter U15 and U16 at pins 11 10 and 9 respectively The switched output of U15 which is analog line D2 appears on J6 pin 9 of the PA exciter interface ribbon cable connector The switched output of U16 w...

Page 41: ...Glenayre Document Number 9110 01002 GL T8541 PA 09 10 99 THEORY OF OPERATION t8541p6 fdk Copyright 1997 Glenayre Page 6 15 v1020 hgl Figure 6 7 Metering Board Fuses Test Points and Jumpers 2000 00601...

Page 42: ...t U3 D sets the conduction of Q1 at a level that causes the voltage drop across R47 to equal the drop across R4 The same current flows through R28 Q1 drain Q1 source and R47 therefore the voltage drop...

Page 43: ...the U9 A compar ator to produce the AGC signal The RF output sample signal is proportional to the transmitter s RF output power level and is obtained from the forward directional coupler The AGC refe...

Page 45: ...Glenayre Document Number 9110 01002 GL T8541 PA 09 10 99 THEORY OF OPERATION t8541p6 fdk Copyright 1997 Glenayre Page 6 19 v1019 hgl Figure 6 11 Metering Board Schematic page 2 of 2 2000 00601...

Page 51: ...Glenayre Document Number 9110 01002 GL T8541 PA 09 10 99 THEORY OF OPERATION t8541p6 fdk Copyright 1997 Glenayre Page 6 25 v0839 hgl Figure 6 17 120 Watt PA Board Schematic 2000 00027...

Page 55: ...s or to perform programming and many of the calibration procedures for this PA A straight through DE 9 to DE 9 cable or an EIA 232 DE 9 to DB 25 adaptor cable is needed to connect from the serial port...

Page 56: ...heat or other anomalies Replace or repair any suspect parts 7 5 Input Voltage Check To be sure that the power amplifier is not operating under adverse electrical conditions or to check the calibratio...

Page 57: ...uts agree and the external wattmeter indication is different a power calibration is needed If the external wattmeter and VDT power output indications agree and both are less than the exciter power set...

Page 58: ...g The RF Output of the PA The setup shown Figure 7 2can be used to calibrate the RF output power level of the PA Follow the forward and reflected power calibration instructions in the DSP exciter VDT...

Page 59: ...ternal wattmeter Refer to the exciter VDT user manual for transmitter operating instructions and to Table 7 1 for the relationship to forward and reflected power levels and the voltage standing wave r...

Page 60: ...isolators and the power output based on 250 watts input The loss of the isolator under test can be calcu lated using the formula below Where LossdB isolator loss in dB Pin power amplifier output power...

Page 61: ...ery small and is proportional to the isolation of the isolator For this test operate the transmitter in the cali bration mode and set the PA output power level to approximately 20 watts refer to the e...

Page 62: ...n be measured with a meter this measurement procedure will be covered in the next section 6 Enter the forward power calibrate mode and key the transmitter key sequence 6 1 7 The driver idle current sh...

Page 63: ...ing board and dc power source Reinstall PA module leaving RF input disconnected 6 Apply power to the transmitter 7 Enter the forward power calibrate mode and key the transmitter key sequence m 5 6 1 8...

Page 64: ...de of Figure 7 6 E Remove power from the transmitter F Remove the meter from the test points G Replace jumper JW1 8 Adjust the Q2 bias using the following sub routine A The exciter RF output should be...

Page 65: ...Glenayre Document Number 9110 01002 GL T8541 PA 09 10 99 CHECKOUT AND MAINTENANCE t8541p7 fdk Copyright 1997 Glenayre Page 7 11 Figure 7 6 Driver Board left and PA BOARD right Layouts...

Page 66: ...log should contain a record or maintenance procedures performed It should also contain a brief description of any troubles encountered the trouble symptoms any repairs performed and any alignment proc...

Page 67: ...s for all PAs possible combiner board discoloration Combiner board RF path problems Replace PA module RF output ok all currents ok excessive harmonic content in output Combiner board low pass filter d...

Page 68: ...metering board jumper JP5 is in position A even when PA temperature is low Open 12 volt metering board regulator Replace metering board 1 RF output normal Driver current at idle value when transmitter...

Page 69: ...Supply Voltage Each PA board and the driver board receives its own fused current monitored 28 volt supply from the metering board The metering board receives its 28 volt supply from the power supply...

Page 70: ...ing the Exciter Output Low RF output from the exciter VCO RF amplifier or a failed cable between the exciter and PA module can cause a low RF output fault on the VDT If either of these conditions are...

Page 71: ...ground pad and center conductor to Q1 RF output pad as shown in Figure 7 9 8 Reinsert the PA module into the transmitter chassis 9 Connect the other end of the coax cable through a wattmeter and to a...

Page 72: ...UT AND MAINTENANCE 09 10 99 Page 7 18 Copyright 1997 Glenayre Figure 7 9 Driver Board Q1 Test Setup Remove RF Jumper Remove L6 To Test To RF Wattmeter Ground Pad and Test Load Coaxial Cable Q1 RF Outp...

Page 73: ...module into the transmitter chassis 8 Connect the other end of the coax cable through a wattmeter and to a 50 ohm test load refer to Figure 7 10 9 Reconnect power to transmitter 10 Go to the calibrate...

Page 74: ...ent Number 9110 01002 CHECKOUT AND MAINTENANCE 09 10 99 Page 7 20 Copyright 1997 Glenayre Figure 7 11 Driver Board RF Output Test Setup Remove RF Jumper To RF Wattmeter Ground Pad and Test Load Coaxia...

Page 75: ...mall increase in the unkeyed AGC voltage for example from 13V to 12V can indicate a failed PA transistor 7 11 3 1 Finding Bad PA board An effective way to find a bad PA board in a PA module with at le...

Page 76: ...002 CHECKOUT AND MAINTENANCE 09 10 99 Page 7 22 Copyright 1997 Glenayre v0838 hgl Figure 7 12 120 Watt PA Board Showing RF Transistor Gate and Drain Pads RF transistor gate pad Measure resistance betw...

Page 77: ...system Also remove all dc power from the PA module before removing PA cover or PA inner PCB cover Note Components on the pc boards require special tools and techniques for replacement Glenayre recomm...

Page 78: ...s and hardware for later reinstallation Remove screws and store for later use 6 The driver board can now be lifted off of the PA module heat sink This procedure is complete 8 4 2 Reinstallation 1 Make...

Page 79: ...procedure is complete 8 5 2 Reinstallation 1 Make certain that there is no grit or other foreign matter in the contact area between power resistors R1 and R2 and the heat sink Apply heat sink compoun...

Page 80: ...plifier board can now be lifted off of the PA module heat sink This pro cedure is complete 8 6 2 Reinstallation 1 Make certain that there is no grit or other foreign matter in the contact area between...

Page 81: ...ard can now be lifted off of the PA module heat sink This procedure is complete 8 7 2 Reinstallation 1 Make certain that there is no grit or other foreign matter in the contact area between R1 the thr...

Page 82: ...fan panel door thumb screws and swing the fan panel door open 4 Remove the PA exciter interface D sub 15 connector from J6 on the metering board Refer to Figure 7 1 for a rear view of the installed me...

Page 89: ...Glenayre Document Number 9110 01002 GL T8541 PA 09 10 99 REMOVAL AND REINSTALLATION t8541p8 fdk Copyright 1997 Glenayre Page 8 13 v1023 hgl Figure 8 7 Metering Board Mounting Diagram...

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