Marconi 2944_2945A Service Manual 电路图.pdf

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1、COMMUNICATIONS SERVICE MONITORS 2944 and 2945A and AVIONICS COMMUNICATION SERVICE MONITOR 2946A IFR. 2002 No pariofthis book may be reproduced or transmuted inanrform or by any means, electronic or meclumical, including photocopying. or recordedbyany information storage orrelril(ilsystem, wilhmf/ pe

2、rmission in writingby FR, PrintedintheUK . Manualpartno. 46882-310 Issue5 23December2002 j RadioFans.CN 收音机爱 好者资料库 Ii About this manual This manual provides servicing information to component level for the Communications Service Monitors2944and2945Aand for the Avionics Communication Service Monitor

3、2946A. Intended audience Thebook is intended for qualified service engineers and assumes a knowledgeofthe instrument10a level covered in Operating Manuals 46882/311, 46882/31;2 and 46882/569. Structure Chapter 1 Technical description Thisincludes block diagrams and detailed board circuit description

4、s.Thecircuit descriptionsreferdirectly to the servicing diagrams contained inChapter7. Chapter 2 Access and layout Refer to thischapterfor board and unit access, service policy and routine safety testing and inspection. Chapter 3 Adjustment and calibration Refer to thischapterfor informationonuser c

5、alibrations, software calibrations and hardware adjustments. Chapter 4 Initial repair Thischapter contains information regarding simple fault finding. Chapter 5 Fault finding The infonnation in this chapter is innowchart form, giving several levelsoffault diagnosis information from very basic repair

6、 down to board component level. Chapter 6 Replaceable parts Contains board component parts and a sectiononmiscellaneous (including mechanical) parts. Chapter 7 servicing diagrams Contains interconnection drawings, board circuits and board component layout drawings. Appendix A Module identification C

7、ontains cross references for module designations andIFRpart numbers. Associated publications Refer to the Operating Manual 46882311 or46882-312for an up to date listofassociated publications. 46882-310 RadioFans.CN 收音机爱 好者资料库 Contents 46682-310 Chapter 1 TECHNICAL DESCRIPTION Backgroundn1-3 Alternat

8、ive boards and assemblies.1-3 Overviewofoperation1-3 Detailed technical description1-7 CONTROL AND MMI1-8 B2/1 Microprocessorboard (44830/110),.1*8 Frontpanel/keyboard (46662/451)1-28 Display(28624308).,:.1-29 Powersupplymodule (44991/179)1-29 RECEIVER SECTION.1-32 All/IInput/outputswitchingBroad ba

9、ndpowermeter (44830-163)1-32 AII/2Input/outputswitchingBroad band powermeter(44830226)132 A21 2 stage inputattenuator (44429/081):1-36 A2 Input mixer(448291922)1-37 A7/1 Ist localoscillatorcontrol (44830/111)1-39 AS/IIst localoscillator (44830/112)1-42 AAIVoltagecontrolled oscillator (41830/160)1-45

10、 A3 2nd for example, B3 only or B3/1 only. Boardsorassemblies that differ significantly from a previous versions are described separately. Other chaptersofthe manual alsocoverall improvementsknownat the timeofpublication. Overview of operation As an introduction to these descriptions, abriefinsighto

11、fthe purposeofthe Service Monitor and its methodofoperation is given.Formore detailed information consult the operating manual. TheCommunications Service Monitor 2945A, is an integrated test instrument primarily designed for testing mobile radio communication equipment.Itis AC mainsorDC battery powe

12、red. The Avionics Communication Service Monitor2946Ais identical to the Communications Service Monitor 2945A, but also includes software for testing receiversforAvionics systems such as ILS, VOR andSELCAL TheCommunications Service Monitor2944is derived fron the 2945A. However some facilities that ar

13、e provided as standardonthe2945Aare offered as optionsonthe 2944. The Service Monitor contains RF and AF signal generator circuits, RF andAFmeasuring circuits, with a back-litLCDdisplayforsetting up test parameters and presenting test results. Alternative oscilloscope and spectrum analyzer display m

14、odes are included. TheSYSTEMtest facility, allows radio communication equipment, designed to function on automatic systems, to be tested using optional programs within the Service Monitor. Amicroprocessorcontrols all functionsofthe instrument. TheService Monitor can be controlled manually from the f

15、ront panel, or remotely usingRS232or GPIB interfaces. Transmitter testing To test a mobile radio transmitter, the Service Monitor produces an AF signal, which is fed to the AF inputofthe transmitter. The RF output from the transmitter is fed to the Service Monitor, usually by direct connection. Freq

16、uency and power measurements are made to the RF signal. Distortion, modulation level,and other measurements are made to the demodulated signal. Theparameters for transmitter testing are set up using the TRANSMITIER TEST screen, accessed by pressing theTxTEST key.Thetest results are also displayedont

17、his screen. Receiver testing To test a mobile radio receiver, the Service Monitor generates anRFtest signal, which is fed to the receiver. usually by direct connection.Thetest signal canbeFMorAM modulated. Thedemodulated output from the receiver is fed to the AF inputofthe ServiceMonitorwhere the pa

18、rametersofthe signal are measured. Theparameters for receiver testing are set up using the RECEIVER TEST screen, accessed by pressing the RxTESTkey.Thetest results are also displayedonthis screen. 46882-3101-3 TECHNICALDESCRIPTION Duplex testing The Service Monitors 2944, 2945Aand 2946A are duplex i

19、nstruments. When carrying out testson duplex transceivers, the Service Monitor is able to generate modulated RF signals,while providing an AF signal to modulate the transmitter. The measuringcircuits are able to make all measurementsto the frequency offset. incoming RF signal, including the demodula

20、ted signal, and to the AF output of the receiver. The frequency offset between the transmit and the receive signalscan also be measured. The RF input and output connectors canbeset for any permutation, to suithueportortwoport connections. When switchingbetweenthe Rx TEST mode, the Tx TEST mode and t

21、he Dx TEST mode, no changes take place to the set-upofthe Service Monitor or to the stateofthe output signals and measurement functions. TheDUPLEXscreen, accessed bypressing the DxTEST key, allows the results of both receiver and transmittertests tobeseen simultaneously. Primary parametersof receive

22、r testingand transmitter testingcanbeset from this screen. Transmitter distortion results and oscilloscope displays are not shownon theDUPLEXscreen. Spectrum analyzer mode TheSPECTRUMANALYZERmode of the Service Monitor isaccessed bypressing the SPEC ANA key.Itconfigures the internalcircuits to provi

23、de a display which showssignal strength against frequency. The RF inputsignal is applied to the Y axis of the display, whilethe Service Monitor receiver circuits are repeatedly swept over the requiredfrequency range, in step withthe X axis of the display. Tracking generator This facilityis not stand

24、ardonthe 2944,but is available asOption 28. With the truckinggeneratorfunction active,the output of the Service Monitor RF generator is made to sweep in synchronizationwiththe RF input tuning. This allows the responseof filters and other frequencydependentcircuits tobemeasured and viewed. The tracki

25、ng generatorisactivated from theSPECTRUMANALYZERdisplay. Lookand Listen This facilityis not standard onthe 2944,but is available asOption 27. The Look and Listenmode of the spectrum analyzer, allows the signal tuned to the center frequencyof the display to bedemodulated and fed to the internalloudsp

26、eaker or to the accessory socket. The Look and Listen mode is activated from theSPECTRUMANALYZERdisplay. AFtestlng The AFTEST modeallows the AFgenerators and the AF measuringcircuits tobeused for active testingof audio circuits. The parameters for AF testingare set upusing theAUDIOTESTscreen, access

27、edbypressing the APTESTkey. . . ,i-. I .j3RDLoCAL , ,:;IOSClUATOR , j00 MHI; OPTJPNlImD r.:;:, ,C FII.reR o fiLTERS ,-I3RlH.OCAl. i,iOSClUAIOR ,iIMlutII: _)+J.I.5MHz ,j ir:-h jAIO ! , , I ,;:l ,I I LOOK.U$Tft ,SWEl!INPUT :-,*;,-:,-, . Fig. 1- Simplified blockdiagram , TECHNICAL DESCRIPTION Detailed

28、technical description This technical description of the constituent assemblies of the Service Monitor is sub-divided into the following areas. Control and MMI Receiver Audio processing Signal generator Interfaces Systems The sequence of descriptions forthecircuit sectionsofeach board, follow the flo

29、wofthe relevant circuit diagram sheets from left to right, starting from sheet one. A block diagram showing the RF circuits and the audio processing circuits of the Service Monitor is shown in Fig. 1-1Simplified block diagram.Detailed block diagrams are included in the technical descriptions where n

30、ecessary. Each board description has a table showing the connections toit,with individual pins listed where this is practical. DC voltages, signal frequencies and levels, and control line labels are shown. The DC supply voltages to eachboardare tabulated. with currents shown where this is practical.

31、 8211 CONTROL AND MMI 82/1Microprocessorboard(44830/110) Overview TECHNICAL DESC/lIPTlON Themicroprocessor board is fitted within the undersideofthe top tray.Itcontains the 8OCI88 microprocessorwhichcontrols all functionsofthe Service Monitor, together with the required memoryinthe formof RAM,NOVRAM

32、,EPROMandEEPROM. As well as the microprocessor and memory. this board contains the hardware for mostofthe control and display functionsofthe Service Monitor. Theseare Thecomponents which form the masterclock,used by the microprocessor andotherareasof the Service Monitor. 1/0address decoding. Keyboar

33、d decoding and variable control interpretation. Serialinterfacecontrol. Interface to the parallel,GPIBand memory card options. Analogue measurements,by AtoDconversion. RFattenuatorcontroldrivers. RFfrequencycontrol. Display generation, updating and control; including oscilloscope and spectrum analyz

34、er displays. Cellular and other system test option interfacing, Board replacement Thisboard holds information unique to the particular instrument, and also the current calibration data.Ifthe board is replaced with a substitute board, recalibrationofthe whole Service Monitor willbenecessary.Theunique

35、datacan onlybereplaced at anIFRService Center. SeeChapter3, Adjustment and Calibration. TECHNICALDESCRIPTION Connections (refer to the relevant circuit diagram forpinconnections) B2I1 PLA PLB PLC PLD PLE PLF PLG PLH PLJ PLK PLL PLM PLN PLP PLR PLS PLT PLU PLW PLX PLY SKA Powerralls Fromtheexternalfr

36、equencystandardsocketonthe rearpan,s!. Suppliespowerand frequencycorrectionto the TemperatureControlledcrystal (Xtal)Oscillator or theoptionalOvenControlledcrystal(Xtal)Oscillator.Returns the 10 MHz,TILoutput from the oscillator to the board. Supplies3 individual10 MHzclocksignalsto the RFtray.(A8I1

37、,A9! andA13J1). 50n,OdBm. Singlepin connectionfromtemperaturesensoron 20 dB 50nload. Voltagebelow 2.5 V causesthe overloadwarningto trigger. Multi-pin connectionto Cellularsystemsand memorycard/timestampoptions. Multi-pin connectionto the frontpanelkeyboard. Multi-pin connectionto GPIS/parallelinter

38、laceoption. Voltagesupplyto, and signalingfrom,the rotarycontrol. Multi-pin connectionto RS232interface. Multi-pinconnectionto audio processorboard 81/1. (AlsoseePLM). Multi-pinconnectionfor controlsignalsto RFattenuatorsA20 andA21. Multi-pin connectionto audio processorboard 81/1. (Alsosee PLK). Mu

39、lti-pinconnectionto RFtray assembly Notusedin this instrument. Supplyvoltageto LCDback-flqhtinverter. Powerrail connectionsfrompowersupplyunit. ON/CHARGE and LOWSAIT signalingfrompower supplyunit. Logamplifieroutput signalfrom A4 Supplies10 MHzclocksignalto A15. 50n,0 dBm Carrierdetectionsignalto op

40、tionalCellularSystemsboard, S3. Sweepmodetest point. GoesLOWduring analyzersweep. Altemativeoutputfor 10MHzclock. Notusedon this instrument. VdC 46882-310 Power railEntry pointInsitu currentBoard only current -12 VPLSDins3 and 4400mA250mA +SVPLSoms5 and 6620 rnA580 rnA +12VPLSpins 7 and 8580 mA350mA

41、 OVPLSDins1and 2 A block diagramofthe board, showing the main elementsofthe control and measurement systems, is given in Fig.I-I. 1-9 8211TECHNICALDESCRIPTION Fig.-2Block diagramofcontrolandmeasurement systems 1-1046882-310 TECHNICAL DESCRIPTION Detailed description 8211 46882-310 SupplyVoltages The

42、 +5 V,-12V and +12 V suppliesrequiredfor the board are routed fromthepower supply module through PLS. A branch taken fromeachsupply is given additional filtering to provide a clean supply where required. Voltageregulator,5Volt Voltage regulatorle80provides a noise-free 5 V supply from the +12 V supp

43、ly.Thisprovides the clean supply for theTCXOorOCXO10 MHz crystal oscillator. 10MHzmasterclock The 10MHzinternal frequency standard for the Service Monitor canbeeither the standard Temperature Controlled Crystal Oscillator (TCXO)Xl,ortheoptional Oven Controlled Crystal Oscillator (OCXO). The crystal

44、oscillator is mounted on the frameofthe B tray and connected to theboardthrough PLB. Theclock signalsofvarious frequencies, required for the board and for other areasofthe Service Monitor, are all produced by the master clock circuitsorderived from it.Ifan external frequency standard isconnectedto t

45、he instrument, theTCXOoroexois locked to the external standard. SeeFig. I*3,Block diagramofmaster clock. TCXO The standardTeXOis powered by a regulated 5 V supply to itsveeconnector pin 3.The 10 MHz,TILoutput is from pin 4.Theveconnection to pin I is the control voltage input, mentioned under Freque

46、ncy correction, below.Ifno correction is applied, this will have a norninallevelof+2.5 V. Increasing the control voltage to +5 V will reduce the output frequency by approximately300Hz, while reducing it to 0 V will increase the output frequency by approximately 300 Hz OCXO TheoptionalOCXOrequires a

47、12 V supply, connected throughPLB,pin4.The5 V supply connected to pin 3 is not used in this instrument.Thefrequency control voltage is supplied to it through pin 5, and the 10 MHz,TILoutput to theboardis through pin 1.Ifno correction is applied, this will have a nominal levelof+2.5 V. Increasing the

48、 control voltage to +5 Vwill increase the output frequency by approximately 150 Hz, while reducing it to 0 V will reduce the output frequency by approximately 150Hz. The absenceofR223 when theOCXOis fitted,correctsfor the opposite tuning senseoftheOCXO compared to the TCXO. Frequency correction The

49、frequencyofeither internal frequency standardcanbe corrected to offset any error in its basic frequency. A frequency offset is applied from the frequency standard adjustment screen, accessed by using the HELPISETUPJ.Calibrate, Freq Stnd,key sequence. A security code restricts the useoftheCalibratekey. Detailsoftileuseofall the calibration facilities willbefound in Chapter 3, Adjustments and Calibration. Correctiontothe clock frequency is achieved by applyi