Tektronix 1705A CRT

Theory of Operation

1705A Spectrum Monitor 4-19

Q5 is a currentamplifier feeding the output stage. Q3 and Q4 form apush-pull

output stage. Q3acts as a 2.7 mA constant current pull-up, while Q4 is the

pull-down transistor. C6 speeds up the amplifier by coupling ac signals to the

base of Q3. CR2and R41 protect the amplifier during crt arcing.

The pinout for the CRTis shownin Figure 4-3.

Pin Description

1 Filament(f)

2 Cathode (k)

3 GRID (g1)

4 FOCUS (g3)

5 ASTIG (g4)

6 GEOM (g5)

7 VERTPLATE (y2)

9 VERTPLATE (y1)

11 HORIZ PLATE(x2)

12 1st ANODE (g2)

13 HORIZ PLATE(x1)

14 Filament (f)

12 11

Figure4 -3: Pinout of the CRT Socket

CRT

Contents

Main 1705A Spectrum Monitor i Table of Contents Introduction Section1 Introduction 1--1................................................ Operating Instructions Section 2 Operating Instruction s 2--1....................................... Installation Section 3 Installation 3--1................................................. Theory of Operation Section 4 Theory of Operation 4--1......................................... 1705A Spectrum Monitor iii Checks and Adjustments Section 5 Checks And Adjustments 5--1..................................... iv 1705A Spectrum Monitor Maintenance 6- - 1.......................................... Section 6 Maintenance 6--1................................................ Section 7 Options 7--1.................................................... Replaceable ElectricalParts Diagrams/Circuit Bo ard Illustrations Replaceable Mechanical Parts List of Figures Page List of Tables General Safety Summary ToAvoidFireor PersonalInjury Symbolsand Terms Service Safety Summary Page Preface Page Preface 1705A Spectrum Monitor xv Contacting Tektronix Page Page Page Section 1 Introduction TypicalConfigurations Accessories Standard Accessories Safety Information Optional Accessories 1-4 1705A Spectrum Monitor ELECTRICAL SPECIFICATION Table1- 1: Spectrum Display 1705A Spectrum Monitor 1-5 Table1- 1: Spectrum Display (Cont.) Table1- 2: CRT Display Table1- 3: Power Source 1-6 1705A Spectrum Monitor Table1- 4: Environmental Characteristics Table1- 5: Physical Characteristics Table1- 6: Certifications and Compliances 1705A Spectrum Monitor 1-7 Table1- 6: Certifications and Compliances (cont.) Page APPLICATIONS Locating Satellites Satellite Footprints Using the 1705A for Satellite Communication L- Band Input Signals Zeroing in on a Satellite Locating the Satellite Identifying the Satellite Page TRANSPONDER FindingThe C orrect Transponder Optimize Signal Strength Looking at Exciters with the 70 MHz Input Miscellaneous Uses forthe 1705A 1-18 1705A Spectrum Monitor Page Page Section 2 Operating Instructions Front-panel Controlsand Indicators INPUT FILTER Operating Instructions Tektronix POWER SWEEP DISPLAY INPUT Page Rear- Panel Connectors POSITION INPUTS POWER 12 3 4 POWER 5 6 Powering-up Measurement Graticule VerticalScales Operating Instructions 2-8 1705A Spectrum Monitor Table2- 1: dB Reference Reading in dB VoltageRatio Power Ratio Readingin dB VoltageRatio Power Ratio Reading in dBm v(75)v(50) Reading in dBm v(75)v(50) Horizontal Scales Page 70 MHZ L-BAND Center Frequency Readout Page Page Customizing FrequencyReadout TurningOn or Off Readout Changing Readout Position SPECTRUM SPAN/DIV Changing Readout Frequency 12.00 GHZ Locating Ku -Band Satellite s TestMode Basic Operating Procedure Page Page Page Page Page Page Page Section 3 Installation ElectricalInstallation Mechanical Installation Operating Options Cabinet Options Page Cabinetizing Cabinet Securing Screws Rack Adapter Page Page Custom Installation Page Page Section 4 Theory of Operation Overview Block Diagram RF Input Circuits (Diagram 1) IF Amplifier Circuits (Diagram 2) Sweep Generator Circuits (Diagram 3) Deflection Amplifiers (Diagram 4) Microprocessor (Diagram 5) Front Panel (Diagram 6) Low VoltagePower Supply (Diagram 7) RF Input Diagram 1 High Voltage(Diagram 8) 70 MHz Input L-Band Input IF Amplifier Diagram 2 70 MHz Local Oscillator 2nd Local Oscillator Input Filter,Mixer, and IF Resolution Filter and Log Detector Sweep Generator Diagram 3 Ramp Generator Sweep Shapers GainControl (SPAN/DIV) Bright-U p Generator Deflection Amplifiers Diagram 4 Z-Axis Control Buffers VerticalDeflection Horizontal Deflection Microprocessor Diagram 5 Microprocessor Front Panel Diagram 6 Readout TraceRotate Graticule Lights Indicators,C ontrols, and Switches +18 VoltSupply Low VoltagePower Supply Diagram 7 Line Rectifier and Filter PulseW idth Modulator Output Filters Error Amplifier Feedback Transformer Driver and Peak Detector Output Under-Voltage Shutdown High VoltagePower Supply Diagram 8 HV Osc and Error Amp Power SupplyOutput s Focus Amplifier Grid Drive Circuit Z-Axis Amplifier CRT Page Page Page Section 5 Checks And Adjustments Recommended Equipment List ElectricalInstruments Auxiliary Equipment Performance Check Short-Form Procedure Page Long Form Procedure Checks and Adjustments 5-6 1705A Spectrum Monitor Table5- 1: PreliminaryCont rolSet tings Figure5 -1: Initialequipment connections Page Page Page Page Page Page Page Page Page End of the Performance Check Procedure Adjustment Procedure Short-Form Procedure Long Form Procedure Checks and Adjustments 1705A Spectrum Monitor 5-19 Figure5 -7: Adjustment locations CAUTION MAINS VOLTAG E A1 PWR SPLYBD A3 MAIN BD FRONT Page Page Page Page Page Page Page End of Adjustment Procedure Page Page Page Section 6 Maintenance PREVENTIVE MAINTENANCE Cleaning VisualInspection Static-Sensitive Components TROUBLESHOOTING Performance Checks and Readjustments SPECTRUM SPAN/DIV Diagnostic Routines Page END OF NON VOLATILE <2444> RAM TEST: 2444 TEST GOOD PRESS [INPUT]KEY TO EXIT Page TroubleshootingAids LED and Key Tests Foldout Pages Parts Lists Major Assembly Interconnection General Troubleshooting Techniques Page Power Supply TroubleshootingProcedure Introduction Low VoltsSupply Page High VoltsSupply Focus AmplifierC heck Z-Axis Amplifier Check Grid Drive Check High VoltageOscillator Check CRT VoltageCheck CORRECTIVE MAINTENANCE Obtaining ReplacementParts Components Mechanical Disassembly/Assembly Bezel Removal Graticule Light Removal and Replacement Removal of the CRT Replacing the CRT Removal of the Rear Panel Removal of Front- Panel Assembly Removing the L-Band Tuner Removing the 70 MHz Tuner Removal and Replacement of the Main Board Removal and Replacement of the Power SupplyB oard Removing the LNB Power SupplyB oard REPACKAGING Page Page Page Section 7 Options Field Upgrade Kits Cabinets CRT Options Power Cord Options ORDERING Page Page Section 8 Replaceable Electrical Parts Parts OrderingInformation Using the Replaceable ElectricalParts List Cross Index- Mfr. Code Number to Manufacturer Abbreviations List of Assemblies Column Descriptions Component No. (Column 1) 1705A Spectrum Monitor 8-3 CROSSINDEX - MFR.CODE NUMBER TO MANUFACTURER 8-4 1705A Spectrum Monitor 1705A Spectrum Monitor 8-5 8-6 1705A Spectrum Monitor 1705A Spectrum Monitor 8-7 8-8 1705A Spectrum Monitor 1705A Spectrum Monitor 8-9 8-10 1705A Spectrum Monitor 1705A Spectrum Monitor 8-11 8-12 1705A Spectrum Monitor 1705A Spectrum Monitor 8-13 8-14 1705A Spectrum Monitor 1705A Spectrum Monitor 8-15 8-16 1705A Spectrum Monitor 1705A Spectrum Monitor 8-17 8-18 1705A Spectrum Monitor 1705A Spectrum Monitor 8-19 8-20 1705A Spectrum Monitor 1705A Spectrum Monitor 8-21 8-22 1705A Spectrum Monitor 1705A Spectrum Monitor 8-23 8-24 1705A Spectrum Monitor 1705A Spectrum Monitor 8-25 8-26 1705A Spectrum Monitor 1705A Spectrum Monitor 8-27 8-28 1705A Spectrum Monitor 1705A Spectrum Monitor 8-29 Page Page Page Diagrams/Circuit Board Illustrations Symbols Component Values Assembly Numbers Grid Coordinates Page 1705A Spectrum Monitor A3 Main Board Component Locator Page A3 Schematic Diagram <1> Component Locator Chart Assembly A3 and A5. Partial Assembly A3 also shown on Diagrams, 2, 3, 4, and 5. A5 70 MHz INPUT LOCALOSCILLATOR RF INPUT <1>RF INPUT <1>RF INPUT <1>RF INPUT <1> 70 MHz A570 MHZ TUNER Schematic Diagram <2> Component Locator Chart Assembly A3. Partial Assembly A3 also shown on Diagrams 1, 3, 4, and 5. RESOLUTION FILTER& LOG DETECTOR 10 KHz FILTER 1705ASPECTRUM MONITOR IFAMPLIFIER <2> Schematic Diagram <3> Component Locator Chart Assembly A3. Partial Assembly A3 also shown on Diagrams 1, 2, 4, and 5. FORTHE ORDER OF CALIBRATION. THENUMBERS MAY NOT MATCHTHE NOTE:THE NUMBERS BY ADJUSTMENTSARE SILKSCREENON THE BOARD FOR THE70MHz LINEARITY SECTION. LBAND LINEARITY RAMP GENERATOR SWEEP GENERATOR<3> CONTROL 70 MHz LINEARITY Schematic Diagram <4> Component Locator Chart Assembly A3. Partial Assembly A3 also shown on Diagrams 1, 2, 3, and 5. FILTER DEFLECTION POST REGULATORS <6> LOWPASS Schematic Diagram <5> Component Locator Chart Assembly A3 and A3A1. Partial Assembly A3 also shown on Diagrams 1, 2, 3, and 4. MICROPROCESSOR <3> <3> ROTATION MICROPROCESSOR <5> A2 Schematic Diagram <6> Component Locator Chart The schematic diagram has an alphanumeric grid to assist in locating parts within that diagram. A2 Front Panel Board A4 18V Power Supply Board Assembly A2 and A4. 1705ASPECTRUM MONITOR FRONT PANEL& 18V SUPPLY <6> A1 Power Supply Board Component Locator A1 Power Supply Board LINE RECTIFIER AND FILTER CLAMP ERROR OUTPUT UV SHUTDOWN PULSE WIDTH MODULATOR Schematic Diagram <8> Component Locator Chart A10 CRT Socket Board (Front of Board) A10 CRT Socket Board (Back of Board) Assembly A10. V1 HV OSC & ERRORAMP A10CRT SOCKET BOARD GRID DRIVE CRT Page Page Page Section 10 Replaceable Mechanical Parts Parts OrderingInformation Using the Replaceable MechanicalParts List Cross Index- Mfr. Code Number to Manufacturer Abbreviations Chassis Parts Column Descriptions 1705A Spectrum Monitor 10-3 CROSSINDEX - MFR.CODE NUMBER TO MANUFACTURER 10-4 1705A Spectrum Monitor 1705A Spectrum Monitor 10-5 10-6 1705A Spectrum Monitor 1705A Spectrum Monitor A4 A1 A3 A2 A3A1 A5