Toshiba TW40F80 manual RAY Protection Circuit, X-RAY protection circuit

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7. X-RAY PROTECTION CIRCUIT

7-1. Outline

In case picture tube using high voltage, when high voltage rises abnormally due to components failure and circuit mal- function, there is possible danger that X-RAY leakage in- creases to affect human body. To prevent it, X-RAY protec- tion circuit is equipped.

7-2. Operation

Figure 9-23 shows the circuit diagram. Supposing high volt- age rises abnormally due to some reason, pulse at pin 9 of T461 also rises, and detection voltage ED rectified by D471 and C471 in X-RAY protection circuit rises. When ED rises, emitter voltage of Q464 divided by R459 and R462 becomes higher than [zener voltage (6.2V) of D458 + Q464 VBE ]. This causes Q464 turns on to supply base current to Q463.

Then Q463 turns on. By this Tr6 and Tr6 turn on to make ON/OFF pulse at pin 7of QA01 in low level, Q846 and Q845 turns off, then relay SR81 turns off. Tr6 and Tr7 are in thy- ristor-connection, and 5V of power holds protection opera- tion until main power switch is turned off. During circuit operation, power LED near main power switch blinks turn on and off in red.

Caution:

• To restart TV set, repair failure first.

5V

Z801

15
R9
R10		12V
Tr7
		Q463
R19	C894	Q464	R459

RELAY	Q846	Tr6		14
RELAY
SR80	16	R12	C1			R462
	16	R12	C1		D459	C458
					D459
		Tr5		R879	R468
		Tr5			R468

			R458
Q845	R11	R467	D458
Q845		R467

C459

17

ED

R472 T461

9

D471 C471

Fig. 9-23 X-RAY protection circuit

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Image 79

Contents TW40F80 Contents Wide Aspect Conversion Circuit Failure Analysis Terminal FUNCTION, Description and Block DiagramSection XI Digital Convergence Circuit Section X Deflection Distortion Correction CircuitReduction of Parts Count Section FeatureImproved Serviceability Outline Merits of BUS SystemChassis Model SpecificationsVideo 3 Inputs Front ViewIN-VIDEO Rear View100 Remote Control ViewStarsight Newosd FRO. Surr Chassis LayoutConstruction of Chassis RF AGC Major FeaturesSection II TUNER, IF/MTS/S. PRO Module Circuit Block OutlineAudio Multiplex Demodulation Circuit A.PRO Section Audio Processor A.PRO block diagramConfiguration of the audio circuit and signal flow are given Terminal No Name POP TunerOperation of Channel Selection Circuit SDA SCL MicrocomputerMicrocomputer Terminal Function Terminal Name Function In/Out Logic Remarks Microcomputer Terminal Name and Operation LogicEEPROMQA02 On Screen FunctionSDA System Block Diagram Local key assignment Function Local KEY Detection MethodCode Function Remote Control Code AssignmentTo TV set Custom codes are 40-BFH TV set for North U.S.A Code Function OPT0 OPT1 Models HEX Optional Setting for Each ModelTest Signal Selection Entering to Service ModeService Adjustment Contents to be Confirmed by Customer Failure Diagnosis ProcedureExecuting Self Diagnosis Function Self Check Understanding Self Diagnosis IndicationClearing method of self diagnosis result TV does Not Turned on Troubleshooting ChartYES No Picture Snow Noise No Acception of KEY-INNo Indication On Screen Memory Circuit CheckSection IV DVD Switch Circuit DVD Switch Block Diagram Outline Operation ConfigurationSection V WAC Circuit Outline Circuit OperationWide aspect conversion unit block diagram PB6348 Pin function of TC9097F QFP 80 pin Pin FunctionName Function Names and functions of TC9097FVFL2 TC9097F system block diagram Block DiagramE2PROM OK? Wide Aspect Conversion Circuit Failure Analysis ProceduresRaster Horizontal One Adjustment MethodPrinciples of Operation Section VI Dual Circuit OutlineScreen multi-search process System Component Diagram of Dual Unit Video/Color/Deflection Process Section OSD Sub screen process section Sub Screen Process SectionMain/Sub screen superimposing section Main/Sub Screen Superimposing SectionMPC1832GT Main IC Terminal FUNCTION, Description and Block DiagramDiagram QY01QY01 mPC1832GT pin layout QY03 TC9092AF internal block diagram QY03 TC9092AF pin layout CKW QY03 TC9092AF pin list No Pin name Pin functionMRD1 QY10/QY11 M518221-30ZS internal block diagram Configuration Circuit Description Section VII 3-DIMENSION Y/C Separator Circuit OutlineCircuit Description Terminal description PZ01 Theory of Operation Section Viii Vertical Output Circuit OutlineCircuit Operation Output CircuitActual Circuit Sawtooth Waveform GenerationOutput Output stage power supply voltage Up-and Down-ward Linearity Balance Linearity Characteristic CorrectionProtection Circuit for V Deflection Stop Character Correction Up-and Down-ward Extension CorrectionUZ11BSB +35V Over Current Protection CircuitTheory of Operation UZ22BSDKetsu Raster Position Switching CircuitBasic Operation of Horizontal Drive SignalSection IX Horizontal Deflection Circuit Outline Horizontal Drive CircuitOn period OFF period FBT Signal DEF/POWER PCBHorizontal Output Circuit Operation of Basic CircuitT4~t6 Description of the basic circuit T1~t2T2~t3 T3~t4Linearity Correction LIN Amplitude CorrectionCurve Correction S Capacitor Linearity coil Left-right Asymmetrical Correction LIN coilEHT White Peak Bending Correction CircuitOutline Operation TheoryBlanking Gate Protector Low Voltage ProtectionHigh Voltage DPC Circuit Regulator High Voltage Generation CircuitAFC ABL2. +35V 1. +210VHigh Voltage CR-BLOCK High Voltage CircuitAnode FBT CR-BLOCK E H ActualED’ 23 X-RAY protection circuit RAY Protection CircuitOver Current Protection Circuit Block Diagram Functions and FeaturesOUT Diode Modulator CircuitActual Circuit Later Half Scanning Period Basic Operation and Current PathFirst Half Scanning Period First Half of Scanning Period Later Half of Flyback PeriodP.T Section XI Digital Convergence Circuit Outline PLL ResetMemory PromPicture Adjustment Entering/Exiting Mode Service ModeFirst screen Second screen Initial screenSfull ENT Key function of remote control unitEach Screen Adjustment Method Operation procedureNormal/Full Theater Wide1 Theater Wide 269.5 When Convergence Unit is Replaced When CRT is ReplacedCase Study Adjusting Procedure in Replacing CRT TroubleshootingAdjusting Procedure in Replacing Convergence Unit/Main Def Convergence Output Circuit Convergence Block Diagram Convergence Troubleshooting Chart Main Unit