Video Signal, Failure Detection | JVC 370 SC, 330, 340 SC specification

Chapter 2—Functional Description

Circuit failure detection.

Beam current sense.

Arc protection.

This section uses Figure 2-16 for reference. The description provides information to perform module-level troubleshooting.

Figure 2-16Video Amplifier Board, Block Diagram

Video Signal

The video signal comes directly from the VPB backplane connector via a coaxial cable to the Video Amplifier Board and enters as VIN. The input signal will be a maximum of 1Vpp. The video amplifier takes the input signal, amplifies and level shifts it so that it will be a negative-going 75Vpp signal modulating the +84Vdc black level, and applies this to the cathode of the CRT. In general, the 84Vdc black level will be seen only during the DC Restore interval. Power for the video amplifier is a locally derived 100V that is regulated down from the 107V input from the SPS.

Failure Detection

The Failure Detection circuit senses the health of the video amp's 100V power supply. When the 100V supply falls below about +64V, the normally low /VIDOK signal is pulled high. The /VIDOK signal is then sent to the VPB.

Model 330, 340SC and 370SC Service Manual

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JVC 370 SC, 330, 340 SC service manual Video Signal, Failure Detection

Contents

Hughes-JVC Technology Corporation Model Model 340 SC Model 370 SC Confidential and proprietary information Manufacturer Hughes-JVC Technology Corporation Introduction Safety Equipment Projector Weight Installation Safeguards Ultra Violet and Infrared Light Heat SafeguardsLight Safeguards Fans Viii Power Supply Fluid SafeguardsVentilation and Foreign Object Retrieval Safety Safety Acronyms Used In Manual Updates SafetyHardware Compatibility Software Graphics enhancement Memories Decoder board option Functional Descriptions Contents Cover and Base 1Model 330, 340SC and 370SC System Block Diagrams Electronics Systems Overview External Power Requirements Functional Descriptions System Power Supply System Power STB STB AC Input CRT SCB HDB VDB VPB RTG VAB Arc Lamp Ignitor 4System Power Supply Input/Output Diagram 22-30V depending on projector model High Voltage Power Supply High Voltage Power Supply Functional Descriptions Card Cage 104668 Backplane Board 100571 Circuit Boards Functional Descriptions 10Raster Generation Block Diagram Raster Timing Generator Board RTG p/n 11Raster Timing Generator Block Diagram Sync Detector and Selector Sync Generator Serration and Equalization Lockout Phase Locked LoopVsync Detector, Field Separator, and Mux Adjustment Counters Information Description Serial Communication Outputs Description Raster Timing Generator I/OSystem Controller Board Inputs Description Vertical Deflection Board Video Processor Board Horizontal Deflection Board P/N 102523 HDB Interlocks and Protection Vertical Oscillator 12Horizontal Deflection Board Block Diagram Horizontal Power Supply Horizontal Phase Locked LoopHorizontal Centering Geometric Correction Flyback SwitchingOutput Section Bus Information Description Horizontal Sweep Failure DetectionIIC Horizontal Deflection Board I/O Vertical Deflection Board Inputs Description Raster Timing Generator Inputs DescriptionMain Horizontal Deflection Coils Inputs Description GND Vertical Deflection Board P/N 102521VDB Functional Description 13Vertical Deflection Board Vertical Preamps Sweep Failure Detection Vertical AmplifiersSide Pincushion and Keystone Correction Top and Bottom Pincushion and Keystone Correction Horizontal Linearity Correction Rxcorr Rycorr Gxcorr Gycorr Bxcorr Correction Amplifiers Input Description General I/O Video Processor Board Outputs Description System Controller Board Output DescriptionHorizontal Deflection Board Inputs Description Main Vertical Deflection Coils System Power SuppliesCorrection Coils Interlocks and Shutdowns Functional Descriptions Video Processor Board P/N 104672 VPB Decoder 15Video Processor Board, Block Diagram R Brightness and Contrast Amplifiers Video/Sync MuxSync Strip SG Sync Strip Switch Logic and Video Enable On-Screen SwitchGamma Correction RGB Sensitivity and Threshold Amplifier Dynamic Focus Amplifier ILA Bias Redbias IIC VidokIIC Sweepok IIC Beamdet Raster Timing Generator RthreshGthresh Bthresh Video Amplifier Board Outputs Description Video Amplifier Board Inputs DescriptionExternal Video Inputs Description Decoder Image Light Amplifiers Hdfocus High Voltage Power Supply Outputs DescriptionSystem Power Supply Inputs Description Vdfocus Video Amplifier Board P/N 103567 or 103774 VAB Failure Detection Video Signal Arc Protection DC RestoreEnable Circuit Beam Current Sense General I/O CRTs High Voltage Power SupplyOutput Description System Controller Board P/N 104668 SCB General Functional Description CPU Expanded Memory Working and Compressed Memory DACs Correction Address Generator Overlay Address Generator Overlay Memory IR Interface Overlay InterfaceLED Display Buffers and Logic RS232 Interface Serial Interface IIC Interface Video Processor Board Output Description Video Processor Board Description Corrstrt Vertical Deflection Board Description Dot Matrix Status Display Horizontal Deflection Board Backplane Board p/n RS-232 Interface SignalsIR Interface Relay Lens CRT AssemblyImage Light Amplifier ILA Assembly Optical Section Functional Description Filters infrared light CRT Image FocusesILA Generates high intensity light beam Prism Arc Lamp AssemblyProjection Lens Ultraviolet Filter and Condensing Lens Image Light AmplifierOptical Subassemblies Cold Mirror Functional Description Functional Descriptions Service Cover-Off Power-On Sequence Service Adjustments 1Power Interlock Switch and Main Circuit Breaker CRT Yoke Rotation Service Adjustments Vertical Size Tracking Vertical Linearity Tracking Horizontal Size Tracking ILA Bias Settings CRT Mechanical Focus Service Adjustments Service Adjustments Electronic Focus Front/Rear Jumpers Jumper Settings A R Inverted Vertical Jumpers G2 Setting 10 G2 AdjustmentSensitivity/Threshold Offset Service Adjustments Model 330 Arc Lamp Alignment and Focus Arc Lamp Alignment and Focus Service Adjustments Axis Plate Model 340SC and 370SC Arc Lamp Alignment and Focus Model 340SC and 370SC Arc Lamp Adjustments Arc Lamp Current Adjustment Watts ± 25W Amps Normal Amps Maximum Service Adjustments Maintenance Remove/Replace Before performing any removal and replacement procedures 1Major components of the Model 330 Projector 2Major components of the Model 340SC and 370SC Projectors Ventilation Filters Projector Covers Model 330 Ignitor and Arc Lamp Assembly P/N 900611S Removal Arc Lamp Assembly J503 J504 Ignitor Assembly Output POSInput NEG Interlock Switch Fan Connector Circuit Breaker Mm Set Screw Mounting Screws Collimating Condensing Lens Adjustment To remove the system power supply see -4and -5and Figure System Power Supply Maintenance Electronics Module System and HV Power Supply left side of projector Maintenance Model 330 CRT Removal Cathode Ray Tube CRT Maintenance 10Model 340SC and 370SC CRT Assembly Model 340SC and 370SC CRT Removal Video Amplifier Board VAB To remove the CRT yoke see -9or Figure CRT Yoke High Voltage Power Supply Hvps Card Cage Printed Circuit Boards Image Light Amplifier Assembly Projection Lens 2for reference to part numbers, if necessary SCB Socket Battery Replacement 13System Controller Board Sram Chips Location Description Quantity 330 340SC 370SC Recommended Spares General Information Troubleshooting On-Screen Text Description First Set Power-On Codes Code Description Second Set Code Meaning Description Break Points Break Trap Data from the Diagnostics Menu Resetting the Projector Main Menu Main Menu Structure Cutoff Problem Possible Solution Service Operator Symptom to Manual Check Raster Edge Video image not Correct using P Incushion Squared Adjust Contrast and Brightness No response Set I/R remote dip switch settings Problem Possible Solution Service Operator Symptom to Manual Glossary of Terms CRT Hdtv ISO MTS VHS Secam Freq Vertical Glossary